Pannier rack dropout attachment bolt question.

[James]

It seems to me that many pannier racks attach to threaded dropout eyelet
using what may be described as a "socket head cap screw".

Basically a bolt with an Allen key head.


Would it make sense from an engineering perspective to have a
countersunk hole in the pannier rack arm and use a countersunk cap screw?


FWIW, the heavy steel gravel bike I have, has a pair of threaded holes
in each of the rear dropouts, for which I made a pair of trailer hitch
posts from a piece of 30x4mm flat steel bar and 10mm steel bolt. I
countersunk the holes in the steel bar and Phillips head countersunk cap
screws seem to work a treat. Never come loose though they can't be
tightened as well as an Allen or Torx head.


--
JS

[AMuzi]

Countersinking may help clearance/ snagging/ aesthetics but
not mechanical function.

You'll have more trouble with phillips heads and ULS 'button
heads' than with standard m5 stainless DIN912 full height
socket head cap screws.
https://24-trends.de/rd/st/zylinderkopf/2.jpg

Further dimensions, comparisons:

https://www.aftfasteners.com/socket-cap-screws-dimensions-and-mechanical-properties/

You may have some advantage with 7991 heads countersunk with
matching angle but you have to settle for a smaller fastener
drive key. meh.

Lube your fasteners for best torque.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[Frank Krygowski]

I think what you're proposing would be theoretically better, but the
advantages would be too small to notice.

I've never had a problem with the typical attachment screws for that
purpose. But I've always stayed away from those button heads that take a
3mm Allen key.


--
- Frank Krygowski

[James]

Thanks.

--
JS

[James]

Thanks.

--
JS

[Tom Kunich]

Since the object of a rack is to hang pannier's on it, I can't see what saving 4 mm on a bolt would be. James is pulling a trailer and again what advantage is gained by using pan heads? Have you ever caught your pants leg on a rack bolt?

[sms]

On 6/24/2021 5:52 PM, James wrote:
> It seems to me that many pannier racks attach to threaded dropout eyelet
> using what may be described as a "socket head cap screw".
>
> Basically a bolt with an Allen key head.
>
>
> Would it make sense from an engineering perspective to have a
> countersunk hole in the pannier rack arm and use a countersunk cap screw?

Are you assuming that the racks weight limit could be increased by the
use of a countersunk cap screw? Or that countersunk screws would be less
likely to loosen?

You'd have to increase the thickness of the end of the rack arm in order
to have enough metal for a countersunk bolt.

BTW, if anyone is looking for flange, washer, metric, Stainless Steel
Allen Head bolts, see
<https://www.aliexpress.com/item/32988120188.html>. I like these bolts
for racks and water bottle cages. No need for separate washers.

[Lou Holtman]

Are you saying that you order a couple of bolts from Aliexpress?

Lou

[Sir Ridesalot]

I'm not an engineer of bicycle parts. However, in my opinion I think that in order to have a countersunk hole in a rack leg, that you'd need to make the rack leg thicker so that the countersunk hole doesn't make it weaker. I'd never countersink any hole on an existing rack leg.

Cheers

[Lou Holtman]

From an engineering point of view countersunk screws suck. The centerline of the countersunk part always has a little offset from the cylindrical part of the hole/thread. When you tighten the screw the part always moves a little bit and/or put unnecessary stress on the bolt head. Maybe not that important in case of a bicycle rack but certainly when you need to position a part with an accuracy of a couple of 0.1 mm.

Lou

[AMuzi]

That's probably right for cap screws. Where we need a
countersink fastener, we typically use a centerdrill:

https://3.imimg.com/data3/AL/AF/MY-3838818/centre-drill-bit-500x500.jpg

with a 7991 screw:
http://www.celticfasteners.co.uk/ekmps/shops/43b1f6/images/m10-x-100-skt-csk-a2-304-stainless-steel-to-din-7991-packed-in-10-s-1710-p.jpg

Which seems accurate enough for bicycle applications,
typically on aluminum gear tabs not high-load applications.

[Lou Holtman]

You are right for bicycle application. I'm in the 0.1 mm business ;-)

Lou

[sms]

On 6/26/2021 12:55 AM, Lou Holtman wrote:

<snip>

> Are you saying that you order a couple of bolts from Aliexpress?

Yes, because the availability of metric fasteners in the U.S. is very
limited. I have an industrial fastener supplier very close to me and
they have no metric, flange head or truss head bolts other than Philips
head. For metric Allen head bolts they have button head available.

If I order from eBay they also come from China.

I have enough of each common size and length to last me a very long time!

[jbeattie]

On Saturday, June 26, 2021 at 11:29:08 AM UTC-7, sms wrote:
> On 6/26/2021 12:55 AM, Lou Holtman wrote:
>
> <snip>
> > Are you saying that you order a couple of bolts from Aliexpress?
> Yes, because the availability of metric fasteners in the U.S. is very
> limited. I have an industrial fastener supplier very close to me and
> they have no metric, flange head or truss head bolts other than Philips
> head. For metric Allen head bolts they have button head available.

Really, I can get metric screws at the neighborhood Ace hardware store. This is pre-remodel: https://fastly.4sqi.net/img/general/width960/12901589_94eiDUskb0yEciXlUOqUy1EGEsTrTgV6m4Lnpm0vFjY.jpg Two aisles of fasteners and tons of metric. I've gotten a bunch of M5 cap and button-head screws from that store, even some M4 and smaller for the odd-ball BB fender boss on the old Roubaix and some other fittings. I doubt they have washer-head, but I haven't checked. I usually just use a washer.

And your industrial fastener store must totally suck because M5 screws of every head type are easily available in Portland. https://www.oregonbolt.com/linecard We even have a company that makes machine/construction bolts -- you can have your company logo embossed on a bolt head. https://www.portlandbolt.com/products/bolts/ Not that you need giant bolts.

Buying locally is probably not as cheap as buying a gross of Chi-screws from Alibaba, but they are available in the US, and we're not even talking about the US internet giants like McMaster-Carr. I can't imagine that SCV doesn't have some M5 cap screws and washers sitting around.

-- Jay Beattie

[Tom Kunich]

We can usually go down to the local hardware store and get stainless metric screws off the shelf with no trouble.

[Tom Kunich]

On Saturday, June 26, 2021 at 11:29:08 AM UTC-7, sms wrote:

Has it even crossed your mind to go down to the local Ace Hardware Store?

[Frank Krygowski]

On 6/26/2021 2:29 PM, sms wrote:
> On 6/26/2021 12:55 AM, Lou Holtman wrote:
>
> <snip>
>
>> Are you saying that you order a couple of bolts from Aliexpress?
>
> Yes, because the availability of metric fasteners in the U.S. is very
> limited. I have an industrial fastener supplier very close to me and
> they have no metric, flange head or truss head bolts other than Philips
> head. For metric Allen head bolts they have button head available.

https://www.mcmaster.com/screws/system-of-measurement~metric/


--
- Frank Krygowski

[Frank Krygowski]

Around here, hardware stores vary greatly in their selection of metric
fasteners. Lowe's pickings are pretty slim. Ace hardware is much better.
Menards is excellent. And this place, Hartville Hardware, is amazing.
https://www.hartvillehardware.com/

They claim to be the largest hardware store in the U.S. I doubt that,
but still...


--
- Frank Krygowski

[Tom Kunich]

Around here they used to have OSH which was spotty since they often took their time re-ordering metric stock. But Ace has always been a winner.

[John B.]

I'm not sure that you are 100% correct as I've certainly used counter
sinks that had a pilot on them to assure that the "counter sink" was
centered on the hole.
--
Cheers,

John B.

[John B.]

On Sat, 26 Jun 2021 11:29:02 -0700, sms <scharf...@geemail.com>
wrote:

Really? You don't have a "screw shop" in your town? Everywhere I've
been there was a shop selling nuts, bolts and machine screws. The best
one I came across was a small shop in Singapore where the guy told me
that they even have Whitworth in "about all the sizes" :-)
--
Cheers,

John B.

[Jeff Liebermann]

On Sat, 26 Jun 2021 08:37:43 -0700 (PDT), Lou Holtman
<lou.h...@gmail.com> wrote:

>From an engineering point of view countersunk screws suck. The centerline of the countersunk part always has a little offset from the cylindrical part of the hole/thread. When you tighten the screw the part always moves a little bit and/or put unnecessary stress on the bolt head. Maybe not that important in case of a bicycle rack but certainly when you need to position a part with an accuracy of a couple of 0.1 mm.

I agree. However, I don't think the problem is excess stress. My
guess is that badly positioned flat head screws look awful and will
certainly incur the wrath of the aesthetics committee. If one must
use flat head screws, floating nuts can deal with the drill position
tolerance:
<https://www.google.com/search?q=floating+nuts&tbm=isch>
<https://catalog.pemnet.com/viewitems/floating-self-clinching-fasteners-a4-as-ac/floating-self-clinching-fasteners-a4-as-ac-metric>

Note: Using a countersink to mill a slot to deal with the problem is
a really bad idea.

--
Jeff Liebermann je...@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

[John B.]

On Sat, 26 Jun 2021 20:10:52 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>On Sat, 26 Jun 2021 08:37:43 -0700 (PDT), Lou Holtman
><lou.h...@gmail.com> wrote:
>
>>From an engineering point of view countersunk screws suck. The centerline of the countersunk part always has a little offset from the cylindrical part of the hole/thread. When you tighten the screw the part always moves a little bit and/or put unnecessary stress on the bolt head. Maybe not that important in case of a bicycle rack but certainly when you need to position a part with an accuracy of a couple of 0.1 mm.
>
>I agree. However, I don't think the problem is excess stress. My
>guess is that badly positioned flat head screws look awful and will
>certainly incur the wrath of the aesthetics committee. If one must
>use flat head screws, floating nuts can deal with the drill position
>tolerance:
><https://www.google.com/search?q=floating+nuts&tbm=isch>
><https://catalog.pemnet.com/viewitems/floating-self-clinching-fasteners-a4-as-ac/floating-self-clinching-fasteners-a4-as-ac-metric>
>
>Note: Using a countersink to mill a slot to deal with the problem is
>a really bad idea.

Rather then floating nuts why not just a bolt with a nut on the end.
Assuming, of course, that one can get to both sides of the stay :-)
--
Cheers,

John B.

[sms]

We have one industrial fastener store, but the selection of Allen head
metric bolts is limited <https://www.olander.com/products/sockets/>. We
have an Ace Hardware store and a Tru-Value hardware store with a limited
selection of metric fasteners. No truss head or flange head metric bolts
with an Allen head though you can find some Philips head versions.

We once had a store called "Mr. Metric" that offered a lot of metric
fasteners but they closed. We had an electronics surplus store that had
a mess of fasteners, some metric, but they closed.

I prefer not to have to add washers to cages and racks and I prefer
everything on the bicycle to be Allen head and stainless steel.

Also, if I do buy metric Allen head bolts at a hardware store they cost
close to $1 each, besides not having a head that is the best for
fastening accessories.

If I buy them from Olander there's a $5 per line item minimum (they got
tired of end users coming in to buy one 20￠ item and instituted that
policy a few years ago). Also at Olander you can't order online, you
have to submit an RFQ and they call you back with a quote and you have
to give them your credit card number over the phone (pre-Covid you could
go to the counter and buy stuff, not sure if they've reopened).

So the bottom line is that to get the ideal metric fasteners for bicycle
stuff, you have to order from somewhere outside the U.S.. And it's no
big deal, as long as you're not in a big hurry. A set of two bottle cage
bolts, with the proper head, can cost you close to $5 on Amazon
<https://www.amazon.com/dp/B07Z6J6W9R>.

[Jeff Liebermann]

On Sun, 27 Jun 2021 12:08:13 +0700, John B. <sloc...@gmail.com>

Actually, neither my floating nut or your bolt, two washers, lock
washer and nut sandwich will work. I forgot to look at the original
problem before getting involved in the flat head screw solution. The
original problem was to attach "many pannier racks attach to threaded
dropout eyelet". In other words, the dropout is already threaded and
a nut is not necessary. Something like this:
<https://cdn.shopify.com/s/files/1/0081/1222/files/TIGHTENEYELET.gif>
Since there is only one screw involved, there's no alignment or
tolerance problem.

If the aluminum rack were countersunk for a flat head screw, it would
probably work. However, the head would be about 10mm in diameter[1]
for a 90 degree screw head angle[2]:
<https://i394.photobucket.com/albums/pp29/monsterbolts/SpecSheets/DIN7991_M5.jpg>
The lugs on my rear rack are 12mm wide, leaving only about 1mm of
aluminum on the sides. Countersinking is going to remove quite a bit
of aluminum from the rack lugs. The M5 FH screw should fit and hold
(thanks to friction on the sides of the screw head), but might deform
the aluminum lug if over-tightened. It's like driving a wedge into
the aluminum. If the rack lugs were wider or harder, FH might work,
but at 12mm wide, I don't like it.


[1] M5 FH Head diameter can be 9.75mm to 11.20mm.

[2] Note that US flat head screws most commonly have a head angle of
82 degrees. Choose your hardware and countersink wisely because M5 FH
and 10-32 FH threads are almost interchangeable, except for the head
angles.

[Jeff Liebermann]

On Thu, 24 Jun 2021 22:31:49 -0400, Frank Krygowski
<frkr...@sbcglobal.net> wrote:

>I've never had a problem with the typical attachment screws for that
>purpose. But I've always stayed away from those button heads that take a
>3mm Allen key.

Agreed. Perhaps Torx screws? I have a few Torx screws on my
bicycles, but no flat heads. Torx M5 flat heads, in stainless of
course:
<https://www.mcmaster.com/torx-screws/thread-size~m5/head-type~flat/material~stainless-steel/>

[Frank Krygowski]

Long ago, I wanted my fenders to be easily removable. A trick I used was
to insert a mounting screw into the threaded hole starting from the
inside. That formed a threaded stud facing out. Then a wing nut held the
fender in place.

Since then, I just leave the fenders on all the time. And I know there
are fender clips that allow the fender stays to pop out easily, which is
probably a better solution.

(I never used that "stud" trick with a rack that would carry a heavy load.)


--
- Frank Krygowski

[jbeattie]

You should consider: https://road.cc/content/review/192758-sks-raceblade-propro-xl These are actually great fenders. I have a set that I pop-on the gravel bike when my son comes to visit in the rainy-season. Coverage is excellent, and they are easy-on, easy-off and highly adjustable.

BTW, I'm hiding inside from the sun. It's like Phoenix in Portland with no AC. I would much rather have a winter storm, assuming no threat of roof collapse from snow, etc. The big snow dump this killed three azaleas that got buried for a week, which made me sad, but this heat is probably going to kill a lot more than that.

-- Jay Beattie.

[AMuzi]

Standard equipment for Nottingham built Raleighs with solid
strut mudguards. Very handy, never saw one break.

This is not original but shows the concept clearly:
https://live.staticflickr.com/3434/3365268610_25e9b5e92c.jpg

[AMuzi]

Agree on SKS Race Blades. Clever, useful, great for the
mechanically disinclined. Now available in fat besides race
bike models.

[Frank Krygowski]

On 6/27/2021 12:19 PM, jbeattie wrote:
> On Sunday, June 27, 2021 at 8:36:05 AM UTC-7, Frank Krygowski wrote:
>>
>>> Rather then floating nuts why not just a bolt with a nut on the end.
>>> Assuming, of course, that one can get to both sides of the stay :-)
>> Long ago, I wanted my fenders to be easily removable. A trick I used was
>> to insert a mounting screw into the threaded hole starting from the
>> inside. That formed a threaded stud facing out. Then a wing nut held the
>> fender in place.
>>
>> Since then, I just leave the fenders on all the time. And I know there
>> are fender clips that allow the fender stays to pop out easily, which is
>> probably a better solution.
>
> You should consider: https://road.cc/content/review/192758-sks-raceblade-propro-xl These are actually great fenders. I have a set that I pop-on the gravel bike when my son comes to visit in the rainy-season. Coverage is excellent, and they are easy-on, easy-off and highly adjustable.

As I said, I just leave them on all the time now. The only disadvantage
I see is very occasional, when I want to fit my back inside our
hatchback. I easily take off the front wheel, but the front fender
prevents the bike from laying as flat as I like.

Don't those Race Blades allow rear wheel water to sling forward onto the
chain and your feet?

> BTW, I'm hiding inside from the sun. It's like Phoenix in Portland with no AC. I would much rather have a winter storm, assuming no threat of roof collapse from snow, etc. The big snow dump this killed three azaleas that got buried for a week, which made me sad, but this heat is probably going to kill a lot more than that.

Yes, we talked to a Portlander yesterday about that. My sympathies! It
just hit 91 F here, and I just turned on the AC for the first time this
year. If my wife were a little tougher I wouldn't have needed to do even
that.

--
- Frank Krygowski

[Jeff Liebermann]

On Sun, 27 Jun 2021 01:12:15 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>If the aluminum rack were countersunk for a flat head screw, it would
>probably work. However, the head would be about 10mm in diameter[1]
>for a 90 degree screw head angle[2]:
><https://i394.photobucket.com/albums/pp29/monsterbolts/SpecSheets/DIN7991_M5.jpg>
>The lugs on my rear rack are 12mm wide, leaving only about 1mm of
>aluminum on the sides. Countersinking is going to remove quite a bit
>of aluminum from the rack lugs. The M5 FH screw should fit and hold
>(thanks to friction on the sides of the screw head), but might deform
>the aluminum lug if over-tightened. It's like driving a wedge into
>the aluminum. If the rack lugs were wider or harder, FH might work,
>but at 12mm wide, I don't like it.

I found another problem with using flat head screws. The aluminum
rack thickness will probably not be thick enough to clear the M5 FH
screw head height. I just measured my rack lugs at 2.3mm thick.
<http://www.learnbydestroying.com/jeffl/pics/bicycles/Bor_Yueh/index.html#Bor_Yueh_04.jpg>
From:
<https://i394.photobucket.com/albums/pp29/monsterbolts/SpecSheets/DIN7991_M5.jpg>
the M5 FH screw head height is 3.1mm. Installing such a screw will
cause the head to hit the threaded lug before it tightens on the rack
lug. In other words, the screw can't be tightened on the rack lug. A
thicker "heavy duty" aluminum pannier rack lug might work. A stack of
5mm washers would work, but that defeats the purpose of using a flat
head screw.

I just noticed that I specified the wrong M5 FH screw type (DIN 7991).
I originally found a FH M5 screw with a shoulder, where the threads do
NOT extend all the way to the base of the head. That's not going to
work. This DIN 965 screw would be a better choice:
<https://cdn.shopify.com/s/files/1/1818/5247/files/Phil_FLAT_M5_spec_1024x1024.jpg>
The screw dimensions are slightly smaller. The head is about 9mm
diameter and head height is 2.5mm. This screw will still bottom out
on the threaded lug before it can be tightened on a 2.3mm thick
aluminum rack lug. Better, but not good enough.

[Sir Ridesalot]

My concern if countersinking on a rack leg not designed for a countersink, is that it might weaken the strut a lot at the point where the countersink is.

Cheers

[AMuzi]

>"Don't those Race Blades allow rear wheel water to sling forward?

Minimal spray compared to any other 'mini' mudguard system.
Not as good as classic 28" Roadster steel mudguards but the
SKS actually fit race bikes, quickly and easily.
Impressively light weight too.

For certain riders, no waiting for a hardware packet from
china. Bonus!

[AMuzi]

IME common DIN fasteners relevant to bicycle accessories
(m4, m5, m6) are offered full thread or partial. I linked a
chart the other day but the Inter Webs are full of DIN
screws, many many permutations.

[Jeff Liebermann]

On Sun, 27 Jun 2021 12:46:35 -0700 (PDT), Sir Ridesalot
<i_am_cyc...@yahoo.ca> wrote:

>My concern if countersinking on a rack leg not designed for a countersink, is that it might weaken the strut a lot at the point where the countersink is.
>Cheers

Yep, that's one problem with a flat head screw. I mentioned it in my
previous rant as:

"The lugs on my rear rack are 12mm wide, leaving only about
1mm of aluminum on the sides. Countersinking is going to
remove quite a bit of aluminum from the rack lugs."

However, the problem of the M5 FH screw head hitting the threaded
dropout before it can clamp down on the aluminum rack leg lug makes
the thinned and weakened material problem irrelevant. Either way, an
M5 FH screw is not going to work without a redesign of the pannier
rack leg lug.

I probably should have asked this earlier, but what problem are you
trying to solve?

[Jeff Liebermann]

On Sun, 27 Jun 2021 15:02:07 -0500, AMuzi <a...@yellowjersey.org> wrote:

>IME common DIN fasteners relevant to bicycle accessories
>(m4, m5, m6) are offered full thread or partial. I linked a
>chart the other day but the Inter Webs are full of DIN
>screws, many many permutations.

I hereby confess to being guilty of missing the obvious. Notice that
I posted the first message at 1:20AM. I was mostly asleep and trying
to recover from what I believe was a failed cooking experiment. I was
looking for something to do in a roughly vertical position to prevent
acid reflux problems. About two hours later, I finally fell into bed.
Sorry, but I couldn't think of anything better to do at the time than
to answer Usenet questions. I'll try to be more awake next time.

[AMuzi]

On 6/27/2021 3:15 PM, Jeff Liebermann wrote:
> On Sun, 27 Jun 2021 12:46:35 -0700 (PDT), Sir Ridesalot
> <i_am_cyc...@yahoo.ca> wrote:
>
>> My concern if countersinking on a rack leg not designed for a countersink, is that it might weaken the strut a lot at the point where the countersink is.
>> Cheers
>
> Yep, that's one problem with a flat head screw. I mentioned it in my
> previous rant as:
> "The lugs on my rear rack are 12mm wide, leaving only about
> 1mm of aluminum on the sides. Countersinking is going to
> remove quite a bit of aluminum from the rack lugs."
>
> However, the problem of the M5 FH screw head hitting the threaded
> dropout before it can clamp down on the aluminum rack leg lug makes
> the thinned and weakened material problem irrelevant. Either way, an
> M5 FH screw is not going to work without a redesign of the pannier
> rack leg lug.
>
> I probably should have asked this earlier, but what problem are you
> trying to solve?
>

If I recall, OP wondered about advantages to countersinking
rack fasteners, if any. We all tried to dissuade him in one
way or another. As with everything RBT, conversation
digressed. Which is good!

[Jeff Liebermann]

On Sun, 27 Jun 2021 12:46:35 -0700 (PDT), Sir Ridesalot
<i_am_cyc...@yahoo.ca> wrote:

Will these "decorative" FH countersunk cup washers work?
<https://www.google.com/search?q=flat+head+countersunk+cup+washers+m5&tbm=isch>
<https://www.amazon.com/uxcell-Screw-Aluminum-Countersunk-Washers/dp/B01JVHCDWK>
The nice part is you don't need to countersink the aluminum rack ends.
My rack mount is 12.3mm wide (measured). These washers are 12mm wide,
so it should fit without a hangover, err... overhang.

For reinforcing a countersunk hole, maybe flush finishing washers?
<https://www.google.com/search?q=flush+finishing+washer+m5&tbm=isch>
However, countersinking might still weaken the pannier rack lug hole.
I don't know exactly how to make these work, but I thought you might
find them interesting.

[Jeff Liebermann]

Guilty again. I didn't read the entire thread before I replied. I
won't apologize and promise to be good because it will probably happen
again.

A dash of topic drift: When I was designing marine radios, I had to
deal with various mechanical designers, industrial designers and
consultants. All of them tended to design packages that were similar
to those of their previous employer. Whether their experience was
appropriate was not considered debatable. One mechanical designer
came from the flush rivet school of aircraft design and systematically
redesigned a few products so that they could use flush flat head
screws. These required much tighter tolerances than the previous
hardware, which was reflected by a spectacular increase in packaging
costs. There were also assembly problems from production and dealers.
As the de facto damage control engineer, it was my job to fix the
problems (without changing anything). I systematically removed all
the flat head screws from the design and replaced them with pan head.
The complaints magically faded away.

I forgot to mumble something about flat head screws being terrible for
waterproofing, which is a basic requirement for most marine radios.

[Lou Holtman]

On Sunday, June 27, 2021 at 11:03:17 PM UTC+2, jeff.li...@gmail.com wrote:
> On Sun, 27 Jun 2021 12:46:35 -0700 (PDT), Sir Ridesalot
> <i_am_cyc...@yahoo.ca> wrote:
> Will these "decorative" FH countersunk cup washers work?
> <https://www.google.com/search?q=flat+head+countersunk+cup+washers+m5&tbm=isch>
> <https://www.amazon.com/uxcell-Screw-Aluminum-Countersunk-Washers/dp/B01JVHCDWK>
> The nice part is you don't need to countersink the aluminum rack ends.
> My rack mount is 12.3mm wide (measured). These washers are 12mm wide,
> so it should fit without a hangover, err... overhang.

Those are nice washers but as you mentioned they are decorative. It would be strange to use these in a normal application because you use a countersunk bolt in case it has to be flush with the surface of the part. In all other application a countersunk bolt is not the first choice.

Lou

[James]

On 28/6/21 8:21 am, Lou Holtman wrote:

>
> Those are nice washers but as you mentioned they are decorative. It
> would be strange to use these in a normal application because you use
> a countersunk bolt in case it has to be flush with the surface of the
> part. In all other application a countersunk bolt is not the first
> choice.
>

I wondered about the sensibility of using a countersunk head for a
couple of reasons. First so that there is more friction between the
screw head and rack such that the probability of the screw working loose
is lessened, and second so that there is practically no way that while
the fastener is not loose that the rack could move against the frame
while the bike is ridden over bumpy ground.


Clearly using a regular bolt there must be clearance between the rack
and bolt shank or threads, and if the bolt is not quite tight then over
bumpy ground there is a possibility that the rack could move relative to
the eyelet. A CS head should fix that I would have thought.

FWIW I'm planning a multi day tour that will take me over some gravel
roads and there are few towns so that I will carry camping equipment and
food for the trip.

--
JS

[Frank Krygowski]

Thank Goodness for my non-racing bikes!


--
- Frank Krygowski

[Frank Krygowski]

Instead of countersinking, I'd use thread locker on the screws and carry
a few extra screws plus the appropriate tightening tool.

Granted, those would weigh even more than my few salt packs! But I bet
you can manage the extra weight. ;-)


--
- Frank Krygowski

[John B.]

On Sun, 27 Jun 2021 01:12:15 -0700, Jeff Liebermann <je...@cruzio.com>

For attaching things to bicycle frames I have always relied on
threaded "bushings" whether brazed on the outside of the tube or flush
with the outer diameter of the tube and for fasteners I've always used
fillster head Allen "screws". Never had one come loose yet :-)

A #5 alloy steel machine screw has a shear strength of ~1,325 lbs and
a #6 ~1,615. In stainless it is unlisted for the #5 and ~375 for the
#6.
O.D. #5 - 0.125", #5 - 0.138
https://www.aftfasteners.com/socket-cap-screws-dimensions-and-mechanical-properties/
--
Cheers,

John B.

[AMuzi]

Ah there's the rub.

If people could manage shear loading in their various
arrangements we would not be discussing it here. Adding the
rack out some place beyond mudguard stays is common. But
also flexy racks themselves put a not-ideal load on bolts.

[Jeff Liebermann]

On Mon, 28 Jun 2021 07:49:30 +0700, John B. <sloc...@gmail.com>
wrote:

>For attaching things to bicycle frames I have always relied on
>threaded "bushings" whether brazed on the outside of the tube or flush
>with the outer diameter of the tube and for fasteners I've always used
>fillster head Allen "screws". Never had one come loose yet :-)
>
>A #5 alloy steel machine screw has a shear strength of ~1,325 lbs and
>a #6 ~1,615. In stainless it is unlisted for the #5 and ~375 for the
>#6.
> O.D. #5 - 0.125", #5 - 0.138
>https://www.aftfasteners.com/socket-cap-screws-dimensions-and-mechanical-properties/

Ummm... we were discussing metric screws, specifically M5 for pannier
mount. A #5 screw is a smaller diameter US standard screw thread.

I just wasted 30 mins looking for metric socket head screws on the AFT
Fasteners web pile. Time to look elsewhere:
<https://www.bayoucitybolt.com/socket-head-cap-screws-metric.html#cap-mech>
For socket head cap screws, 2nd table from the bottom shows:

M5-0.8 Single shear strength threads 10.7 kN = 2,400 lbs
M5-0.8 Single shear strength body 13.4 kN = 3,012 lbs

M6-1.0 Single shear strength threads 15.2 kN = 3,417 lbs
M6-1.0 Single shear strength body 19.5 kN = 4,384 lbs

I think the bicycle rack will bend or break before an M5 cap screw
fails.

[James]

Carrying spares doesn't bother me, however if the plan is to notice a
missing bolt then try to replace it, irreversible damage may have
occurred to the rack (bending due to the pannier weight and rough road)
and the eyelet as the bolt slops about.


The best plan is to use a design with least chance of failure in the
first place.

--
JS

[John B.]

On Sun, 27 Jun 2021 20:23:53 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>On Mon, 28 Jun 2021 07:49:30 +0700, John B. <sloc...@gmail.com>
>wrote:
>
>>For attaching things to bicycle frames I have always relied on
>>threaded "bushings" whether brazed on the outside of the tube or flush
>>with the outer diameter of the tube and for fasteners I've always used
>>fillster head Allen "screws". Never had one come loose yet :-)
>>
>>A #5 alloy steel machine screw has a shear strength of ~1,325 lbs and
>>a #6 ~1,615. In stainless it is unlisted for the #5 and ~375 for the
>>#6.
>> O.D. #5 - 0.125", #5 - 0.138
>>https://www.aftfasteners.com/socket-cap-screws-dimensions-and-mechanical-properties/
>
>Ummm... we were discussing metric screws, specifically M5 for pannier
>mount. A #5 screw is a smaller diameter US standard screw thread.
>

Certainly. I found the reference which listed U.S. sizes (and
admittedly being lazy) but even gave you the diameter. But, to avoid
confusion I probably I should have shows the strength of a #10 (US)
screw which is very close to a 5mm screw and has a shear strength of
2,060 lbs for alloy and 950 for aluminum,
#10 dia - 0.190", 5MM - 0.196

>I just wasted 30 mins looking for metric socket head screws on the AFT
>Fasteners web pile. Time to look elsewhere:
><https://www.bayoucitybolt.com/socket-head-cap-screws-metric.html#cap-mech>
>For socket head cap screws, 2nd table from the bottom shows:
>
>M5-0.8 Single shear strength threads 10.7 kN = 2,400 lbs
>M5-0.8 Single shear strength body 13.4 kN = 3,012 lbs
>
>M6-1.0 Single shear strength threads 15.2 kN = 3,417 lbs
>M6-1.0 Single shear strength body 19.5 kN = 4,384 lbs
>
>I think the bicycle rack will bend or break before an M5 cap screw
>fails.
--

Cheers,

John B.

[James]

On 28/6/21 5:21 pm, John B. wrote:

> Certainly. I found the reference which listed U.S. sizes (and
> admittedly being lazy) but even gave you the diameter. But, to avoid
> confusion I probably I should have shows the strength of a #10 (US)
> screw which is very close to a 5mm screw and has a shear strength of
> 2,060 lbs for alloy and 950 for aluminum,
> #10 dia - 0.190", 5MM - 0.19

"Alloy". Very few metals we use are pure. They're practically all alloys.

In Australia if you mention "alloy rims" people think aluminium alloy!

Did you mean steel?

--
JS

[sms]

On 6/27/2021 9:40 PM, James wrote:

<snip>

> Carrying spares doesn't bother me, however if the plan is to notice a
> missing bolt then try to replace it, irreversible damage may have
> occurred to the rack (bending due to the pannier weight and rough road)
> and the eyelet as the bolt slops about.
>
>
> The best plan is to use a design with least chance of failure in the
> first place.

True, that's why thread lock compound, or a flanged lock-nut (if there
is space) in addition to the M5 bolt into the threaded frame, is a good
idea to avoid lost bolts, <https://www.mcmaster.com/metric-locknuts/> or
<https://www.aliexpress.com/item/32977028879.html>.

I once fixed someone's lost rack bolt with a cable tie, good enough for
a temporary fix.

[sms]

On 6/26/2021 11:29 AM, sms wrote:
> On 6/26/2021 12:55 AM, Lou Holtman wrote:
>
> <snip>
>
>> Are you saying that you order a couple of bolts from Aliexpress?
>
> Yes, because the availability of metric fasteners in the U.S. is very
> limited. I have an industrial fastener supplier very close to me and
> they have no metric, flange head or truss head bolts other than Philips
> head. For metric Allen head bolts they have button head available.
>
> If I order from eBay they also come from China.
>
> I have enough of each common size and length to last me a very long time!

I do see that McMaster also offers Allen head bolts with a wide flange
head, but they are quite expensive, over $4 each
<https://www.mcmaster.com/metric-locknuts/metric-stainless-steel-ultra-wide-flanged-button-head-screws/>.

[Tom Kunich]

On Sunday, June 27, 2021 at 1:30:31 PM UTC-7, jeff.li...@gmail.com wrote:
> On Sun, 27 Jun 2021 15:02:07 -0500, AMuzi <a...@yellowjersey.org> wrote:
>
> >IME common DIN fasteners relevant to bicycle accessories
> >(m4, m5, m6) are offered full thread or partial. I linked a
> >chart the other day but the Inter Webs are full of DIN
> >screws, many many permutations.
> I hereby confess to being guilty of missing the obvious. Notice that
> I posted the first message at 1:20AM. I was mostly asleep and trying
> to recover from what I believe was a failed cooking experiment. I was
> looking for something to do in a roughly vertical position to prevent
> acid reflux problems. About two hours later, I finally fell into bed.
> Sorry, but I couldn't think of anything better to do at the time than
> to answer Usenet questions. I'll try to be more awake next time.

I made the mistake of having a cup of coffee when fighting that stupid handlebar. So I got little sleep last night and the my dinner was very slow to digest. Shit happens.

[Tom Kunich]

Well, I do have a touring bike. But I haven't ridden it in a couple of years. I'm not touring and it just sits in the back yard under cover. Only since the last one was stolen, I now keep a lock on the gate when I'm not out riding. I suppose I should keep it on all of the time but that would mean leaving my Douglas out in front while I locked the gate and went around through the house. And no one knows its there now unlike the last one where some Hispanic roofer watched me bring the last one in and put it in the back.

[Tom Kunich]

I've done a whole lot of miles with complete camping gear on the racks, including camping stove, tent, sleeping bag, clothing and at least some food and water. So racks are not all that weak.

[Frank Krygowski]

Sure. But I've done lots of miles on gravel, etc. with camping loads. I don't remember ever having a
rack screw loosen. I do use thread locker compound.

I suppose if you were a belt-plus-suspenders guy, you could use a longer mounting screw and add a
Nylock nut on the inside, assuming there's room.

- Frank Krygowski

[John B.]

On Mon, 28 Jun 2021 19:09:14 +1000, James <james.e...@gmail.com>
wrote:

I simply copied what was listed in the text I quoted. But certainly
you do know that the "steel" you mention is an alloy.
--
Cheers,

John B.

[John B.]

On Mon, 28 Jun 2021 08:40:18 -0700, sms <scharf...@geemail.com>
wrote:

Y'all certainly do pay high prices for stuff. The last 5mm machine
screws I bought, admittedly a year or so ago, cost in the neighborhood
of 15 baht (~50 cents) each.
--
Cheers,

John B.

[James]

On 29/6/21 1:50 am, Tom Kunich wrote:

>
> I've done a whole lot of miles with complete camping gear on the
> racks, including camping stove, tent, sleeping bag, clothing and at
> least some food and water. So racks are not all that weak.
>

It has been a long time since I toured with full camping gear, but last
time I did I had a rack break. Unsealed roads put a lot more stress on
racks than smooth bitumen, and I'd like to avoid getting caught out in
the middle of nowhere with no phone reception.

--
JS

[AMuzi]

Each?
They're cheaper per thousand or 5000 or 10000 pieces.

[ritzann...@gmail.com]

Sorry. I just could not resist the comment. I did resist making lots and lots of comments about other Tom posts in this and other recent threads.

"some Hispanic roofer" Are you implying maybe that it was a "Spic" who saw you stash your valuable touring bike in the back yard and it was he who stole your bike? Do you think it was important and crucial to the story that you explicitly identified the roofer as a "Spic"? Just saying "some roofer" would have been inappropriate? Not enough information. Identifying the roofer's race/nationality was a key part of the tale.

[AMuzi]

Good day for it though, Roofs are in the news:

https://www.nationalreview.com/news/national-archives-racism-task-force-labels-own-rotunda-example-of-structural-racism/

The US National Archives reports their building, especially
that racist dome design, is racist and the racist building
is chock full of racist documents written by racists. If
all that's true, then maybe Tom's just trying to fit in.

I don't know about any of it; seems batshit crazy to me.

[John B.]

Well, given that there are about 6 or 10 or so 5mm screws on my bikes
I think that 5,000 might be just a tiny bit of overkill :-)
--
Cheers,

John B.

[sms]

On 6/28/2021 4:20 PM, John B. wrote:

<snip>

> Y'all certainly do pay high prices for stuff. The last 5mm machine
> screws I bought, admittedly a year or so ago, cost in the neighborhood
> of 15 baht (~50 cents) each.

Yes, metric fasteners are ridiculously expensive. If you go to the
hardware store, the SAE fasteners are sold in larger quantities and are
inexpensive. The metric fasteners tend to be sold in tiny bags with one
or two pieces. If you work on bicycles on a regular basis it makes sense
to keep a stock of these.

At one time, a local Japanese "$1.50 store," Daiso, had a hardware
section with a lot of metric fasteners, but no more, see
<https://www.mtbr.com/media/daiso-japanese-imports-cheap-metric-stainless-steel-hardware.1626315/>

[John B.]

But why ever not describe someone in detail? After all the U.S.
government agencies differentiate between "White", "Black or
African American" and "Hispanic or Latino" when describing homicides.
--
Cheers,

John B.

[John B.]

And, just think, terms like "elderly", “handicapped” and “illegal
alien” are also derogatory.

But obviously the designation of the "dome" on a building as
"structural racism" is even more despicable as it must indirectly
refer to Italians as the Romans were the first builders in the history
of architecture to realize the potential of domes for the creation of
large and well-defined interior spaces.
--
Cheers,

John B.

[John B.]

On Mon, 28 Jun 2021 17:03:37 -0700, sms <scharf...@geemail.com>
wrote:

Cultural prejudice. Over here we use both metric and "the other
system". My wife happily buys cloth in either yards or meters and
seems to calculate the required quantity without counting on her
fingers and machine screws seem to priced by their physical size
rather then whether metric or inches.
--
Cheers,

John B.

[AMuzi]

'illegal alien' is in the statute. It's not pejorative.


The Republic and even the Empire welcomed all. Obey Roman
law and speak Latin (or Greek) and you're OK. Good system.

[AMuzi]

Out here in Nowhere, away from the Left Coast, metric
hardware is cheap and plentiful at locally owned Ace and
TruValu stores. Never been in a 'big' hardware store so I
can't speak to that.

[Radey Shouman]

$0.50 sounds like a real first world price.

https://www.boltdepot.com/Metric_socket_cap_Stainless_steel_18-8_(A-2)_5mm_x_0.8mm.aspx

[AMuzi]

They're something like $12 each in Santa Clara but they're
certified organic and are served with avocado toast.

[ritzann...@gmail.com]

Yes race, gender, and other things are recorded for many instances. Usually these indicators are used later for categorization. Or researchers can use them for drawing conclusions or correlations amongst events. Take prisoners. A Google search (evil according to Tom) shows about 1.8 million incarcerated in the USA. 38% are black. 35% are white. 21% are hispanic. And a few more percents to get up to 100%. The recent census also recorded the race, ethnicity of people. A census.gov website I found had the following results. 60% white. 18.5% hispanic. 13.4% black. 5.9% asian. 1.3% indian. I am not vouching for the accuracy of any of the numbers I just typed. I am just restating what I found using Google. But in this instance, prison population, it is useful to know the race of the prisoners and the total population. And then use that information to figure things out. Its appropriate to identify race.

Another example. Andy runs a bike shop. I am sure he keeps track or notices in the back of his mind the race, ethnicity of his customers. Percentage wise. Who buys the most new bikes? Who accounts for most of the repair work? And he can maybe use that information to improve his business. Somehow. So race, ethnicity is appropriate to keep track of. Maybe not officially recording it but just in the back of the mind type data.

But Tom, being Tom, brings in race, ethnicity, to his stolen bike story. I am guessing that he conjured up the story that the roofers in the neighborhood were spying on him (deep state Qanon) and watched him put his unlocked bike in the backyard. Easy to steal his precious bike. Maybe that is a plausible story. But does the race, ethnicity, of the roofers matter to his story? If they had been white caucasian roofers then he would not even have thought up the story. Or if they were asian roofers he would have assumed they were PhD students working summer jobs for their Stanford school. But hispanic roofers and stolen bike fit together tighter than a now old school JIS taper bottom bracket and crank arm.

Other example. Color of cars involved in accidents. I am sure the color of cars in wrecks is recorded on police reports. And time of day, night, too. Now I doubt the color of a car has any affect to a wreck. How much damage is done. How many people are injured or severity of injury. But color of vehicle and time of day might correlate so a researcher can say light colored cars, white cars, have fewer accidents at night when visibility is low. Maybe. So color of car maybe is correctly recorded in accidents. Does race of driver in an accident matter? Can we use that information to correlate bad/good driving to race? Not sure. But I suspect the race of the driver is also recorded in car accidents. Maybe irrelevant data.

[ritzann...@gmail.com]

What????????? John Menard (I think that is his name) the founder of Menards home improvement hardware store is from Wisconsin. He is a homegrown business hero for Wisconsin. Competing against that evil foreign Home Depot and Lowes. You've never been in a Menards store?

[James]

If it was pure it would be iron (Fe).

--
JS

[Frank Krygowski]

I'm curious about the details of the rack breakage.

I broke an early Blackburn rack decades ago. That had one center top strut facing forward, then bending
down, ending with a hole that allowed it to be held in place by a caliper brake's center mounting stud.
On the top of that strut was the name "Jim Blackburn" (IIRC) stamped deeply into the aluminum. The rack
failed by fatigue at the "J."

I wanted to keep it for my class because it was a perfect example of the dangers of a stress riser, but to
get a warranty replacement I had to return it.

None of that had anything to do with the mounting screw choices, though, which is why I'm curious
about your experience.

- Frank Krygowski

[AMuzi]

> What????????? John Menard (I think that is his name) the founder of Menards home improvement hardware store is from Wisconsin. He is a homegrown business hero for Wisconsin. Competing against that evil foreign Home Depot and Lowes. You've never been in a Menards store?
>

Nope. Never. I just wouldn't.

I have very good customers who own franchise hardware stores
including some quite formidable:
https://mcfarlanesinc.com/

The past 100+ years have been very good for the family
who've run it since 1917. Does Mr Menard ride?

[AMuzi]

IME racks fail primarily by being loose and rocking against
the mounting bolt until the aluminum breaks at the thin
spot. Other diverse failures are much less common. Rear
carriers without regular cargo last virtually forever.

[John B.]

No it is simply a statement of fact... which seems to becoming rare in
the U.S. in these modern times.

>
>The Republic and even the Empire welcomed all. Obey Roman
>law and speak Latin (or Greek) and you're OK. Good system.

In the 1st century it is estimated that of the Roman population as
many as 1/3rd were slaves.

And as for living happily under Roman rule if you spoke Latin, not so.
In fact there were very different laws for citizens and non-citizens.
For example citizens could not be crucified and even among citizens,
notably during the Republic, there were at least three different
levels of citizenship each with their own rights and privileges.
--
Cheers,

John B.

[AMuzi]

Yes, a different culture in a different time, and not
without flaws. But the principle of open citizenship not
determined by birth was notable and admirable, especially then.

[John B.]

And, perhaps, a more rational view of things. Remember that when a
General was granted a "Triumph there was a guy crouched in the rear of
the chariot whispering the General's ear as they paraded through the
streets, "Remember, you are only a man".
--
Cheers,

John B.

[James]

Mine suffered a weld (or welds) failure. Probably one weld failed and
before I noticed others had too.

It wasn't the mounting screws that came loose, but then the tours I went
on didn't include more than a few kms of gravel. I think I'll have over
100km of gravel at least on this up coming trip, and I don't know the
condition of the road. There could be a lot of corrugations, for example.

--
JS

[Jeff Liebermann]

On Tue, 29 Jun 2021 09:31:22 +1000, James <james.e...@gmail.com>
wrote:

Never mind a stronger rack. Just get a better phone:
<https://satellitephonestore.com/catalog/sale/satellite-phones>

A fun experiment is to measure the g (gravitational) forced acting on
the rack. The easy way is to use a smartphone accelerometer app.
Plenty to choose from:
<https://play.google.com/store/search?q=g force meter&c=apps>
The maximum range of the typical smartphone accelerometer is +/-16g.
Check the smartphone specs to get the real range and be sure to pick
an app that will indicate and record to the range limits.

Load the panniers with some weights. Clamp the smartphone to the rack
frame. Start the recorder and go for a ride or just pickup the
bicycle and drop it on the pavement. Extract the peak vertical
acceleration. The calculated loading is simply the g force times the
mass of whatever you put in the panniers. If the peak load exceeds
the fasteners shear strength, the fasteners will break.

Calculating where the rack will break is far more complexicated. Using
the pannier vendors maximum load specification would be a conservative
start. For example, if the data sheet maximum load capacity is 30Kg,
but you're only carrying 10Kg, then you can bounce over a road that
produces a 3g shock and be within the max load limit. In reality, the
pannier manufacture probably has a fairly large safety limit. For
example, if they have a 300% safety limit, then your 10Kg load can
handle a 9g shock. Unfortunately, the only way to know for sure if
your pannier loading is safe is to test it to destruction, which will
likely be rather expensive. If the rack rails are bent by the test,
you've likely exceeded the maximum load limit.

--
Jeff Liebermann je...@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

[Jeff Liebermann]

On Mon, 28 Jun 2021 22:33:59 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>A fun experiment is to measure the g (gravitational) forced acting on
>the rack. The easy way is to use a smartphone accelerometer app.
>Plenty to choose from:
><https://play.google.com/store/search?q=g force meter&c=apps>

This Android app looks good enough. There's no chart recorder, but it
does show min/max g forces. I strapped my phone to the rear rack and
bounced it on the floor a few times. It peaked at about +0.5g and
-0.5g relative. Note that resting indication is absolute, as in 1g,
not 0g, so come arithmetic is required to obtain relative g forces.
I might try it on my bumpy road with rear panniers this weekend.

[Jeff Liebermann]

On Mon, 28 Jun 2021 19:15:35 -0700 (PDT), Frank Krygowski
<frkr...@gmail.com> wrote:

>I broke an early Blackburn rack decades ago. That had one center top strut facing forward, then bending
>down, ending with a hole that allowed it to be held in place by a caliper brake's center mounting stud.
>On the top of that strut was the name "Jim Blackburn" (IIRC) stamped deeply into the aluminum. The rack
>failed by fatigue at the "J."

Like this rack?
<http://www.bikerecyclery.com/jim-blackburn-rear-pannier-rack-1980s-brake-bridge-mount/>

>I wanted to keep it for my class because it was a perfect example of the dangers of a stress riser, but to
>get a warranty replacement I had to return it.
>
>None of that had anything to do with the mounting screw choices, though, which is why I'm curious
>about your experience.
>
>- Frank Krygowski

[Frank Krygowski]

On Tuesday, June 29, 2021 at 2:14:50 AM UTC-4, jeff.li...@gmail.com wrote:

> On Mon, 28 Jun 2021 19:15:35 -0700 (PDT), Frank Krygowski wrote:
>
> >I broke an early Blackburn rack decades ago. That had one center top strut facing forward, then bending
> >down, ending with a hole that allowed it to be held in place by a caliper brake's center mounting stud.
> >On the top of that strut was the name "Jim Blackburn" (IIRC) stamped deeply into the aluminum. The rack
> >failed by fatigue at the "J."
> Like this rack?
> <http://www.bikerecyclery.com/jim-blackburn-rear-pannier-rack-1980s-brake-bridge-mount/>

No, it was an earlier version. The one you linked has a flat stainless steel strut attached to the brake bridge.
Mine had a round aluminum strut, the same stuff used to make the rest of the rack. And with Jim
Blackburn's name proudly and sharply stamped into it.

The flexibility of that stainless steel arm is probably an advantage regarding fatigue.

- Frank Krygowski

[jbeattie]

Was it a weld failure? If it had the solid bridge mount, that was an early rack. https://www.ebay.com/itm/Vintage-Blackburn-Rack-RARE-1st-Ed-Welded-Original-Correct-Collector-/283644564564 I had one, too, purchased in '75-76 from PAB and that I used for Canada and US tours and owned until recently. I had a friend who worked for Blackburn welding racks and used to see Blackburn running around SJ in his van making deliveries -- or whatever he was doing. That first design transitioned to the adjustable SS mount really quickly -- like by 78(?) or maybe even earlier. That rack was light years ahead of Pletcher and the other common racks on the market, but it was not bullet proof -- and there are some current racks that could carry elephants.

-- Jay Beattie.

[Frank Krygowski]

On Tuesday, June 29, 2021 at 8:22:52 AM UTC-7, jbeattie wrote:

> On Tuesday, June 29, 2021 at 7:24:11 AM UTC-7, wrote:
> > On Tuesday, June 29, 2021 at 2:14:50 AM UTC-4, jeff.li...@gmail.com wrote:
> > > On Mon, 28 Jun 2021 19:15:35 -0700 (PDT), Frank Krygowski wrote:
> > >
> > > >I broke an early Blackburn rack decades ago. That had one center top strut facing forward, then bending
> > > >down, ending with a hole that allowed it to be held in place by a caliper brake's center mounting stud.
> > > >On the top of that strut was the name "Jim Blackburn" (IIRC) stamped deeply into the aluminum. The rack
> > > >failed by fatigue at the "J."
> > > Like this rack?
> > > <http://www.bikerecyclery.com/jim-blackburn-rear-pannier-rack-1980s-brake-bridge-mount/>
> > No, it was an earlier version. The one you linked has a flat stainless steel strut attached to the brake bridge.
> > Mine had a round aluminum strut, the same stuff used to make the rest of the rack. And with Jim
> > Blackburn's name proudly and sharply stamped into it.
> >
> > The flexibility of that stainless steel arm is probably an advantage regarding fatigue.
> Was it a weld failure? If it had the solid bridge mount, that was an early rack. https://www.ebay.com/itm/Vintage-Blackburn-Rack-RARE-1st-Ed-Welded-Original-Correct-Collector-/283644564564

That was the one, and it was not a weld failure. It was a classic fatigue failure with easily visible "beach marks" in the fracture,
starting (IIRC) at the sharp notch of the "J" where his name was stamped into the strut.

- Frank Krygowski

[sms]

Ace and Tru Value out here have stacks of drawers with metric fasteners,
but the selection is quite limited, and the per piece price is
outrageous. You can buy Philips truss head metric bolts, but not Allen
truss head which is what is preferable for bottle cages, racks, and some
other accessories.

I bought a Blackburn kickstand for one bike and the M6x25 bolts it came
with were too long and were hitting the rear disc. I needed M6x20. I had
to wait two weeks for the proper bolts from Aliexpress, I could have
used less than optimal bolts from Ace Hardware.
<https://i5.walmartimages.com/asr/b3f2a5ad-6128-4ccd-9a9b-273810a27335.f2bb461d2a99972911e79edc8e164f3e.jpeg>.

[Radey Shouman]

You need to acquire something like this:

https://www.metricscrewandtool.com/product-page/screw-cutter-wire-crimper

Works like a charm in minutes, not weeks.

[Ralph Barone]

Only shears bolts up to M5.

I don’t know about anybody else, but I’ve had my best luck at marine supply
places. Lots of metric hardware, and mostly stainless steel.
https://www.stevestonmarine.com

[sms]

On 6/29/2021 12:31 PM, Ralph Barone wrote:

<snip>

> I don’t know about anybody else, but I’ve had my best luck at marine supply
> places. Lots of metric hardware, and mostly stainless steel.
> https://www.stevestonmarine.com

Yes, I agree. Unfortunately the two marine supply stores in my area
closed their stores. The closest ones still open are a little far to be
driving to to buy a bolt.

<https://www.westmarine.com/buy/fasco-fastener--stainless-steel-metric-cap-screws--P005377650>.

We had a great hardware store in Fremont which had a good selection of
metric fasteners but it closed a couple of years ago.
<https://www.yelp.com/biz/mcivor-hardware-fremont-2>.

[jbeattie]

Where do you live again? Bhutan? Its always amazing for me to hear that you don't have bike shops, real hardware stores with fasteners or marine supply stores -- or whatever store we happen to be discussing at the moment. What has happened to the SCV? We had plenty of those things when I was growing up down there. Is it all porn shops and cannabis dispensaries? Apple Stores? Louis Vuitton? This bizarre lack of bikes and fasteners makes me wonder if you're not looking very hard. I can walk a half mile or so to an Ace-affiliated hardware store and buy all the metric fasteners I need for my bikes.

-- Jay Beattie..

[sms]

Orchard Supply Hardware had a good selection of metric fasteners but
Lowe's bought the chain and shut it down. Now some of the old OSH stores
are being re-opened as "Outdoor Supply Hardware" and we'll see if they
are as good as the old OSH stores. We're getting one in Sunnyvale pretty
soon, and a new Ace store is taking over an old Rite Aid.

The Ace stores around here have the typical drawers of specialty
fasteners, including some metric hardware, you can get by, but for
Stainless Hex Socket Allen Truss Head Machine Screw, you have to order
online, Ace, Tru-Value, Lowe's, Home Depot, etc., aren't going to work,
and they really gouge on price.

It's better to just keep a small stock of M4, M5, & M6 flange head Allen
bolts so you don't have to keep searching for hardware. It's a lot less
expensive too. <https://www.aliexpress.com/item/32988120188.html>.

[James]

On 29/6/21 4:14 pm, Jeff Liebermann wrote:
> On Mon, 28 Jun 2021 19:15:35 -0700 (PDT), Frank Krygowski
> <frkr...@gmail.com> wrote:
>
>> I broke an early Blackburn rack decades ago. That had one center top strut facing forward, then bending
>> down, ending with a hole that allowed it to be held in place by a caliper brake's center mounting stud.
>> On the top of that strut was the name "Jim Blackburn" (IIRC) stamped deeply into the aluminum. The rack
>> failed by fatigue at the "J."
>
> Like this rack?
> <http://www.bikerecyclery.com/jim-blackburn-rear-pannier-rack-1980s-brake-bridge-mount/>
>

Mine was like that.

--
JS

[James]

On 29/6/21 3:33 pm, Jeff Liebermann wrote:

I don't think the bolt is likely to shear. My concern is that it might
work loose and in doing so with vibrations damage the frame, the bolt
and the rack.

My thought was that a countersunk head would be less likely to work
loose and would greatly reduce any movement between the frame and rack.

It seems that people don't think it is an issue, or that I should just
use some thread lock compound instead.

--
JS

[John B.]

On Tue, 29 Jun 2021 11:54:41 -0700, sms <scharf...@geemail.com>

Well, if you want to make a 20 mm bolt out of a 25mm bolt it is fairly
easy to do :-) Assuming that you learned how to do it in your youth
:-) And own a hacksaw and a file :-)

--
Cheers,

John B.

[John B.]

On Tue, 29 Jun 2021 16:43:04 -0700, sms <scharf...@geemail.com>
wrote:

What I've done for years was if I needed to go to the store and buy a
bolt/screw I bought several so now I've got several boxes of nuts and
bolts and screws in various sizes and only rarely do I have to go to
the store for one nut,bolt,washer, etc.
--
Cheers,

John B.

[Jeff Liebermann]

On Wed, 30 Jun 2021 09:49:45 +1000, James <james.e...@gmail.com>
wrote:

>I don't think the bolt is likely to shear. My concern is that it might
>work loose and in doing so with vibrations damage the frame, the bolt
>and the rack.

Lock washers, thread locker or both. I rather like Nord-Lock lock
washers for keeping screws from rattling loose:
<https://www.nord-lock.com/nord-lock/>
However, star type lockwashers should be sufficient. I would avoid
split ring lockwashers.

If there's a nut involved, Nylock nuts:
<https://en.wikipedia.org/wiki/Nyloc_nut>
<https://www.google.com/search?q=nylock+nut&tbm=isch>

>My thought was that a countersunk head would be less likely to work
>loose and would greatly reduce any movement between the frame and rack.

I beg to differ. Countersinking relies on:
1. The angle of the flat head screw is identical to the angle of the
countersunk hole. A few fractions of a degree off in either direction
and the contact surface area of the conical taper will be greatly
reduced. What really keeps FH screws from vibrating loose is
dissimilar metals rusting the screw in place.
2. If the head doesn't hold the screw in place, then tightening the
screw, which stretches the threads, will hold it. However, you have a
sandwich with aluminum in the middle. Aluminum will compress, cold
flow, and not be able to maintain the torque and pressure needed to
stretch (or tension) the screw threads. If it were a steel rack rail,
it would not compress and could be sufficiently tightened.

>It seems that people don't think it is an issue, or that I should just
>use some thread lock compound instead.

I don't think it's an issue in the stock configuration, where several
fastener locking systems will keep the screw in place. However, my
main objections are:
1. The FH screw head is too high and will bottom out on the dropout
before it can be tightened.
2. The amount of aluminum that must be removed to accept a
countersunk screw will severely weaken the rack support.
3. A small improvement in the type of screw head MIGHT also solve the
problem. For example, switching to a cap screw with a Torx head, so
that it could be tightened more than a pan head slot or whatever.
4. If you can't identify the specific cause of the screws falling out
from vibration, then carrying spare hardware might be necessary to
complete the ride. (Most of my shirts come with spare buttons). If
the screws continue to fall out, maybe Pop-Rivets instead of screws.

[Jeff Liebermann]

On Tue, 29 Jun 2021 19:16:03 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>On Wed, 30 Jun 2021 09:49:45 +1000, James <james.e...@gmail.com>
>wrote:
>
>>I don't think the bolt is likely to shear. My concern is that it might
>>work loose and in doing so with vibrations damage the frame, the bolt
>>and the rack.

>Lock washers, thread locker or both. I rather like Nord-Lock lock
>washers for keeping screws from rattling loose:
><https://www.nord-lock.com/nord-lock/>
>However, star type lockwashers should be sufficient. I would avoid
>split ring lockwashers.

Never mind. Too expensive at $23.23 for a package of 10:
<https://www.nord-lock.com/en-us/shop/washers/stainless-steel/nl5ss/>

[Frank Krygowski]

On 6/29/2021 5:25 PM, jbeattie wrote:
> On Tuesday, June 29, 2021 at 1:03:58 PM UTC-7, sms wrote:
>> On 6/29/2021 12:31 PM, Ralph Barone wrote:
>>
>> <snip>
>>> I don’t know about anybody else, but I’ve had my best luck at marine supply
>>> places. Lots of metric hardware, and mostly stainless steel.
>>> https://www.stevestonmarine.com
>> Yes, I agree. Unfortunately the two marine supply stores in my area
>> closed their stores. The closest ones still open are a little far to be
>> driving to to buy a bolt.
>>
>> <https://www.westmarine.com/buy/fasco-fastener--stainless-steel-metric-cap-screws--P005377650>.
>>
>> We had a great hardware store in Fremont which had a good selection of
>> metric fasteners but it closed a couple of years ago.
>> <https://www.yelp.com/biz/mcivor-hardware-fremont-2>.
>
> Where do you live again? Bhutan? Its always amazing for me to hear that you don't have bike shops, real hardware stores with fasteners or marine supply stores -- or whatever store we happen to be discussing at the moment.

We have fewer bike shops than I like, but we have hardware stores.

Still, I wouldn't bother riding the five minutes to Lowe's to buy 5mm
screws that were a few millimeters shorter. I'd reach into my little
drawer of 5mm screws and find ones the length I needed. The drawer must
have a hundred, mostly taken out of other stuff that was being
discarded, or unused extras that came with some bike component.

If I didn't have the precise length, I'd cut a longer one down. Thread
on a nut, make the cut, grind or file the end clean, remove the nut to
straighten the last thread, and hit it again lightly with a fine file.

Sheesh.

--
- Frank Krygowski