Convert Degrees to Foot Pounds?

9773 views
Skip to first unread message

Kenn E. Thompson

unread,
Nov 26, 2004, 8:22:42 PM11/26/04
to
Working on a Deutz Diesel engine. The instructions say to torque the
bolts to 30 foot pounds then turn 45 degrees.

Can I convert the degrees to foot pounds so I can use a torque wrench
to make them more exact?

Is there an abbreviation for "foot pounds"?

Tom Gardner

unread,
Nov 26, 2004, 9:11:47 PM11/26/04
to
Do what it says. There are factors that affect torque readings. The
engineers have it right, no sense second guessing them.


"Kenn E. Thompson" <webm...@deltafarms.com> wrote in message
news:96aa2d22.04112...@posting.google.com...

Robert Swinney

unread,
Nov 26, 2004, 9:58:02 PM11/26/04
to
Yep. It is probably easier to turn 45 degrees and stop rather than to
"torque" to some specified final amount.

Bob Swinney
"Tom Gardner" <tom(nospam)@ohiobrush.com> wrote in message
news:DnRpd.209$nE7...@newssvr17.news.prodigy.com...

DoN. Nichols

unread,
Nov 26, 2004, 9:54:28 PM11/26/04
to
In article <96aa2d22.04112...@posting.google.com>,

Kenn E. Thompson <webm...@deltafarms.com> wrote:
>Working on a Deutz Diesel engine. The instructions say to torque the
>bolts to 30 foot pounds then turn 45 degrees.
>
>Can I convert the degrees to foot pounds so I can use a torque wrench
>to make them more exact?

No -- that would be making them *less* exact.

Do you have an old school protractor? (The D-shaped thing with
angles marked on it in degrees.) Use your torque wrench as instructed
to tighten to 30 foot pounds, and then place the protractor to measure
the angle of the wrench handle. Turn it an extra 45 degrees (1/8 of a
full turn). This part is to stretch the bolt after you get it to that
torque starting point. And that bolt should *never* be re-used -- you
stretch it once, no more.

>Is there an abbreviation for "foot pounds"?

"Ft-Lbs" is one.

Enjoy,
DoN.

--
Email: <dnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Anthony

unread,
Nov 26, 2004, 11:24:02 PM11/26/04
to
webm...@deltafarms.com (Kenn E. Thompson) wrote in
news:96aa2d22.04112...@posting.google.com:


They are not wanting a specific 'torque' on the bolt, they want a
specific amount of bolt stretch, or yield. You torque it to 30 to get it
to the initial point, then they want it stretched by x mm, which is 1/8
of the pitch. So say for a M8x1.5 this is going to be .1875 mm of
stretch, after the 30 lb-ft of torque are applied. As I believe Don said,
NEVER, NEVER reuse a torque+stretch bolt. They are designed to stretch
ONCE. They WILL FAIL if stretched a second time.
And yes, technically, it is lb-ft, not ft-lbs.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

Old Nick

unread,
Nov 26, 2004, 11:49:24 PM11/26/04
to
On 26 Nov 2004 17:22:42 -0800, webm...@deltafarms.com (Kenn E.
Thompson) vaguely proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

You are far better off simply doing as they say.

I was amazed when I started looking at tightening techniques. I have
an industrial fastener reference from a largish nuts and bolts firm
here in Oz. In it they say that "guess work" by the operator is on
average 35% inaccurate and that's plus or minus!....and the torque
wrench is 25% ! Turn of nut (your need) is 15%. So actually, guessing
is less harmful over torque wrenches than torque wrenches over turn of
nut! <G>

Then you get down to really careful, $$ stuff like strain gauges,
special washers that show tension etc. Lastly are Strain Gauges, which
these guys say are within 1%.

Tim Williams

unread,
Nov 26, 2004, 11:51:59 PM11/26/04
to
"Anthony" <tonyt...@hotmail.com> wrote in message
news:Xns95ADEED67544...@216.77.188.18...

> And yes, technically, it is lb-ft, not ft-lbs.

3 * 4 = 4 * 3. ;^)

Tim

--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms


Leo Lichtman

unread,
Nov 27, 2004, 1:57:14 AM11/27/04
to

"Tim Williams" wrote: 3 * 4 = 4 * 3. ;^)
^^^^^^^^^^^^^^
That's the reciprocity law, and it applies to addition and multiplication.
However, there is a HUGE difference when you are dealing with vectors. If
the vectors are colinear, you get WORK, and by convention it is labelled
foot-pounds. If the vectors are at right angles, you get TORQUE, and label
it pound-feet. The labelling is arbitrary, but important. :-)


ATP

unread,
Nov 27, 2004, 7:54:11 AM11/27/04
to

"DoN. Nichols" <dnic...@d-and-d.com> wrote in message
news:co8q94$bt4$1...@fuego.d-and-d.com...

> In article <96aa2d22.04112...@posting.google.com>,
> Kenn E. Thompson <webm...@deltafarms.com> wrote:
> >Working on a Deutz Diesel engine. The instructions say to torque the
> >bolts to 30 foot pounds then turn 45 degrees.
> >
> >Can I convert the degrees to foot pounds so I can use a torque wrench
> >to make them more exact?
>
> No -- that would be making them *less* exact.
>
> Do you have an old school protractor? (The D-shaped thing with
> angles marked on it in degrees.) Use your torque wrench as instructed
> to tighten to 30 foot pounds, and then place the protractor to measure
> the angle of the wrench handle. Turn it an extra 45 degrees (1/8 of a
> full turn). This part is to stretch the bolt after you get it to that
> torque starting point. And that bolt should *never* be re-used -- you
> stretch it once, no more.
>
Doesn't every bolt stretch when you torque it down? How are these
fundamentally different?


Jeff R.

unread,
Nov 27, 2004, 8:34:08 AM11/27/04
to

"ATP" <walter...@unforgiven.com> wrote in message
news:8Q_pd.4230$M36....@fe12.lga...

Also...
Doesn't this assume that these bolts are tightened past their elastic limit?
Past their UTS?

Surely not...

==
Jeff R.


Jeff R.

unread,
Nov 27, 2004, 8:37:05 AM11/27/04
to

"Jeff R." <conta...@this.ng> wrote in message news:41a88252$0$17543

> Doesn't this assume that these bolts are tightened past their elastic limit?
> Past their UTS?

Brain fart.
I meant "Yield Stress"

(oops)


Anthony

unread,
Nov 27, 2004, 9:05:24 AM11/27/04
to
"Jeff R." <conta...@this.ng> wrote in
news:41a88302$0$20863$afc3...@news.optusnet.com.au:

The tightening technique is to get the bolt very near the yield point,
and not over it. However, if you reuse the bolt, you will exceed the yeld
point. This will result in insufficient clamping pressure for the joint,
and could (very likely, actually) result in broken fastners.

The torque technique is becoming industry standard nowadays, and that is
because it is inherintly more accurate.
If you torque a bolt to 70-80 lb-ft, the inaccuracies of the measurement
grow expotentially as you increase torque due to friction, head galling,
lubrication distribution and other variables during the tightening. By
keeping the measured torque lower, you reduce these inaccuracies
substantially. By specifying the angle of final placement from a lower
given torque, you use the thread pitch to determine the linear stretch
amount for the fastener.

Tim Williams

unread,
Nov 27, 2004, 11:43:19 AM11/27/04
to
"Leo Lichtman" <l.lic...@worldnet.att.net> wrote in message
news:ezVpd.983262$Gx4.2...@bgtnsc04-news.ops.worldnet.att.net...

> If the vectors are colinear, you get WORK, and by convention it is
labelled
> foot-pounds. If the vectors are at right angles, you get TORQUE, and
label
> it pound-feet. The labelling is arbitrary, but important. :-)

I'm well aware of the dot vs. cross product, but didn't know the order of
the units mattered at all... interesting!

Now if only I would remember that bit of trivia. ;-p

Tim Wescott

unread,
Nov 27, 2004, 12:11:01 PM11/27/04
to
Tim Williams wrote:

Mathematically they don't matter -- and if you depend on convention then
you'll just get screwed up by the person who's document you're reading
who didn't know the convention.

Best to understand what you're looking at, and assume that the
manufacturer _probably_ knew what they were talking about.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Ken Davey

unread,
Nov 27, 2004, 1:31:50 PM11/27/04
to
DoN. Nichols wrote:
> In article <96aa2d22.04112...@posting.google.com>,
> Kenn E. Thompson <webm...@deltafarms.com> wrote:
>> Working on a Deutz Diesel engine. The instructions say to torque the
>> bolts to 30 foot pounds then turn 45 degrees.
>>
>> Can I convert the degrees to foot pounds so I can use a torque wrench
>> to make them more exact?
>
> No -- that would be making them *less* exact.
>
> Do you have an old school protractor? (The D-shaped thing with
> angles marked on it in degrees.) Use your torque wrench as instructed
> to tighten to 30 foot pounds, and then place the protractor to measure
> the angle of the wrench handle. Turn it an extra 45 degrees (1/8 of a
> full turn). This part is to stretch the bolt after you get it to that
> torque starting point. And that bolt should *never* be re-used -- you
> stretch it once, no more.
>
Precisely!!
Ken.
--
http://www.rupert.net/~solar
Return address supplied by 'spammotel'
http://www.spammotel.com


Ken Davey

unread,
Nov 27, 2004, 1:33:40 PM11/27/04
to
The Eleventh Commandant:
THOU SHALT NOT ASSUME!
Regards.

Leo Lichtman

unread,
Nov 27, 2004, 4:59:46 PM11/27/04
to

"Tim Wescott" wrote: (clip)if you depend on convention then you'll just
get screwed up by the person who's document you're reading who didn't know
the convention.(clip)
^^^^^^^^^^^^^^
I would certainly not adhere to the convention if the context indicated
otherwise. I was responding to Tim Williams post, and it turns out that he
knew this as well. So..."Never mind."


Old Nick

unread,
Nov 27, 2004, 5:02:40 PM11/27/04
to
On Sat, 27 Nov 2004 14:05:24 GMT, Anthony <tonyt...@hotmail.com>

vaguely proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

>The tightening technique is to get the bolt very near the yield point,
>and not over it. However, if you reuse the bolt, you will exceed the yeld
>point. This will result in insufficient clamping pressure for the joint,
>and could (very likely, actually) result in broken fastners.

AFAICS, you shouldn't exceed the yield point if you use the bolt
again. The whole idea of Yield point (and I am prepared to learn
another lack in my "knowledge base here, believe me" is that it's the
point at which the steel deforms permanently. Any bolt tightened to
below the yield will return to its former length. (???)

I can see two possible problems. Metal fatigue if the bolt is in place
for an extended time, and / oe under heat/cold/ vibration etc.
Accidental overtightening. Thsi would be an enginerring tning. If the
bolts were _really_ taken to near yield, there would little margin for
error. But once a bolt has exceeded yield, it starts to lose tension
anyway. That woud be dangerous.

Old Nick

unread,
Nov 27, 2004, 5:05:46 PM11/27/04
to
On Sun, 28 Nov 2004 00:37:05 +1100, "Jeff R." <conta...@this.ng>

vaguely proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

>

AFACUI, the answer is still no if you are asking about stretching. A
spring is the most dramatic example of a metal that can be "stretched"
without exceeding yield stress. To stretch steel you need to apply
stress. It will start to stretch under very small stress. It will
_permanently_ stretch when it passes yield.

Old Nick

unread,
Nov 27, 2004, 5:10:58 PM11/27/04
to
On 26 Nov 2004 21:54:28 -0500, dnic...@d-and-d.com (DoN. Nichols)

vaguely proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

>This part is to stretch the bolt after you get it to that


>torque starting point. And that bolt should *never* be re-used -- you
>stretch it once, no more.

Ok. Why should yopu not re-use the bolt? You are only stretching it,
but not to Yield.

I have questioned Anthony about this. My theory says I am right, but
you guys know your stuff. So fact is against me. I am never willing to
let being thought a fool stop me from opening my mouth. I have leraned
a lot that way...

...everything except when to keep my mouth shut! <G>


Lane

unread,
Nov 27, 2004, 7:44:04 PM11/27/04
to

"Old Nick" <nsnsa...@dodo.com.au> wrote in message
news:fmuhq011g31431kq6...@4ax.com...

>
> Ok. Why should yopu not re-use the bolt? You are only stretching it,
> but not to Yield.
>

Metal fatigue plays a factor once the bolt is stretched. I know that there
are a number of engines that use this method in tightening head bolts. And
they are not to be re-used under any circumstances.

Lane


B.B.

unread,
Nov 27, 2004, 9:04:01 PM11/27/04
to
In article <fmuhq011g31431kq6...@4ax.com>,
Old Nick <nsnsa...@dodo.com.au> wrote:

>On 26 Nov 2004 21:54:28 -0500, dnic...@d-and-d.com (DoN. Nichols)
>vaguely proposed a theory
>......and in reply I say!:
>
> remove ns from my header address to reply via email
>
>>This part is to stretch the bolt after you get it to that
>>torque starting point. And that bolt should *never* be re-used -- you
>>stretch it once, no more.
>
>Ok. Why should yopu not re-use the bolt? You are only stretching it,
>but not to Yield.

I think it's because they get hot while under tension and while
getting hammered by the engine. That gives 'em a small amount of work
hardening that won't like a restretch later on.
I read it somewhere on the internet, but then again, I read it
somewhere on the internet.

>I have questioned Anthony about this. My theory says I am right, but
>you guys know your stuff. So fact is against me. I am never willing to
>let being thought a fool stop me from opening my mouth. I have leraned
>a lot that way...
>
>...everything except when to keep my mouth shut! <G>

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

Dan Caster

unread,
Nov 28, 2004, 2:05:49 PM11/28/04
to
Recently I borrowed some material from a friend on bolts and read a
lot of it.
And as usual the answer is " it depends ". Torqueing to a low value
and then tightning a number of degrees was stated as being more
accurate than just using a torque wrench.

But without more information, I can't tell you if these bolts are
being tightned until they yield or not. You can design bolted joints
so that the bolts are tightened unitl they yield slightly, or you can
design joints so they do not tighten the bolts to yield.

But if the original poster has the book that says how to tighten the
bolts, I am pretty sure it would say if the bolts should not be
reused. My SWAG would be that tightening them 45 degrees, probably is
not into yield. On the other hand, using new bolts ( of the correct
grade )will never get you into trouble.

Dan

Old Nick <nsnsa...@dodo.com.au> wrote in message news:<fmuhq011g31431kq6...@4ax.com>...

> Ok. Why should yopu not re-use the bolt? You are only stretching it,

Ted Edwards

unread,
Nov 28, 2004, 3:03:17 PM11/28/04
to
Old Nick wrote:

> again. The whole idea of Yield point (and I am prepared to learn
> another lack in my "knowledge base here, believe me" is that it's the
> point at which the steel deforms permanently. Any bolt tightened to
> below the yield will return to its former length. (???)

Ideally, this is true. i.e. Yield point is stress level that separates
elastic (returns to original dimention when the stress is relieved) from
plastic (returns to original dimention when the stress is relieved)
deformation. Regretably most materials do not behave ideally so you
will often see yield point defined as the point where residual
deformation is some small percentage of original dimension.

Ted


invntrr

unread,
Nov 28, 2004, 6:36:01 PM11/28/04
to

"Dan Caster" <dca...@krl.org> wrote in message
news:3183eab.04112...@posting.google.com...

> Recently I borrowed some material from a friend on bolts and read a
> lot of it.
> And as usual the answer is " it depends ". Torqueing to a low value
> and then tightning a number of degrees was stated as being more
> accurate than just using a torque wrench.
>
> But without more information, I can't tell you if these bolts are
> being tightned until they yield or not. You can design bolted joints
> so that the bolts are tightened unitl they yield slightly, or you can
> design joints so they do not tighten the bolts to yield.
>
> But if the original poster has the book that says how to tighten the
> bolts, I am pretty sure it would say if the bolts should not be
> reused. My SWAG would be that tightening them 45 degrees, probably is
> not into yield. On the other hand, using new bolts ( of the correct
> grade )will never get you into trouble.
>
> Dan

How can you possibly correlate degrees to Ft lbs ? If I torque a 1/4 20..
45 degrees that will be much more torque then torque in a 1/4 28... 45
degrees.
If the manual says torque then turn ...it's already calculated on a fresh
bolt ... however if you reuse a standard bolt it has already been stretched
once ,I would not want to stretch it again.

Old Nick

unread,
Nov 29, 2004, 11:22:16 PM11/29/04
to
On Sun, 28 Nov 2004 20:03:17 GMT, Ted Edwards
<Ted_Es...@telus.net> vaguely proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

>Ideally, this is true. i.e. Yield point is stress level that separates


>elastic (returns to original dimention when the stress is relieved) from
>plastic (returns to original dimention when the stress is relieved)

I am sorry. I am a bit confused by the above lines.

>deformation. Regretably most materials do not behave ideally so you
>will often see yield point defined as the point where residual
>deformation is some small percentage of original dimension.

Which is to say that you use a bolt that only _just_ doesn't really do
the job. <G>

Gary Coffman

unread,
Nov 30, 2004, 11:47:23 AM11/30/04
to

The concept behind stress to yield bolts is to get a very consistent
bolt to bolt torque value when tightened according to the listed
procedure. Many modern head bolts have a reduced diameter section
on the shank for this purpose. Torque variance can be as small as
1% using this method. Ordinary torque wrench methods give a
bolt to bolt consistency variance that is often as large as 20%.
Consistent torque reduces the tendency of aluminum heads to
warp.

Gary

Dan Caster

unread,
Nov 30, 2004, 10:29:53 PM11/30/04
to
"invntrr" <inv...@verizon.net> wrote in message news:<Bhtqd.2617$

>
> How can you possibly correlate degrees to Ft lbs ? If I torque a 1/4 20..
> 45 degrees that will be much more torque then torque in a 1/4 28... 45
> degrees.
> If the manual says torque then turn ...it's already calculated on a fresh
> bolt ... however if you reuse a standard bolt it has already been stretched
> once ,I would not want to stretch it again.

I don't think I said anything about correlating degrees to ft lbs.
But if you have say a 4 inch long 1/4 20 bolt and you tighten it so it
is snug and then tighten it 45 degrees, you will have stretched the
bolt 0.0125 inches. So for a 4 inch long bolt you would have
stretched it .0031 inches per inch of length.
Now assuming this is less than yield, you can loosen it and retighten
it over and over. No new bolt needed. You don't worry about flexing
the springs in your car, do you. Stretching less than yield means it
returns to the original length when the stress is removed.

If you use a different length bolt, or a bolt with different threads
per inch, you have to calculate how many degrees to tighten it for the
stain you want.

Dan

Dan Caster

unread,
Nov 30, 2004, 10:38:43 PM11/30/04
to
dca...@krl.org (Dan Caster) wrote in message news:<3183eab.04112...@posting.google.com>...

> Recently I borrowed some material from a friend on bolts and read a
> lot of it.
> And as usual the answer is " it depends ". Torqueing to a low value
> and then tightning a number of degrees was stated as being more
> accurate than just using a torque wrench.
>
If anyone is interested in knowing more, the author of most of the
articles and books that I borrowed is John H. Bickford. Good books,
just not cheap.

Dan

invntrr

unread,
Nov 30, 2004, 11:09:58 PM11/30/04
to

"Dan Caster" <dca...@krl.org> wrote in message
news:3183eab.04113...@posting.google.com...

> "invntrr" <inv...@verizon.net> wrote in message news:<Bhtqd.2617$
>
> I don't think I said anything about correlating degrees to ft lbs.

The name of the thread is convert degrees to Foot Pounds so I assumed that's
what the subject was ... happens all the time where a thread starts out one
thing and turns into something else.
I guess you have to go back to the original post to figure out where the
subjects at ... I don't because some of the threads are really long.

DoN. Nichols

unread,
Nov 30, 2004, 11:07:55 PM11/30/04
to
In article <3183eab.04113...@posting.google.com>,

Dan Caster <dca...@krl.org> wrote:
>"invntrr" <inv...@verizon.net> wrote in message news:<Bhtqd.2617$
>
>>
>> How can you possibly correlate degrees to Ft lbs ? If I torque a 1/4 20..
>> 45 degrees that will be much more torque then torque in a 1/4 28... 45
>> degrees.
>> If the manual says torque then turn ...it's already calculated on a fresh
>> bolt ... however if you reuse a standard bolt it has already been stretched
>> once ,I would not want to stretch it again.
>
>I don't think I said anything about correlating degrees to ft lbs.

*You* didn't -- but it is in the "Subject: " header from the
original question.

>But if you have say a 4 inch long 1/4 20 bolt and you tighten it so it
>is snug and then tighten it 45 degrees, you will have stretched the
>bolt 0.0125 inches. So for a 4 inch long bolt you would have
>stretched it .0031 inches per inch of length.

And to calculate the equivalent foot-pounds figure, you would
need to know the diameter of the section being stretched, the length of
the reduced diameter or section being stretched, and the tensile
strength at the current temper of the material. (And, as has already
been discussed, trying to do it all with a torque wrench is less
accurate.

>Now assuming this is less than yield, you can loosen it and retighten
>it over and over. No new bolt needed. You don't worry about flexing
>the springs in your car, do you. Stretching less than yield means it
>returns to the original length when the stress is removed.
>
>If you use a different length bolt, or a bolt with different threads
>per inch, you have to calculate how many degrees to tighten it for the
>stain you want.

*Or* -- a different reduced diameter length, if present. And
that would be more likely to be a torque to yield bolt application.

Enjoy,
DoN.

--
Email: <dnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

e

unread,
Nov 30, 2004, 11:57:09 PM11/30/04
to
webm...@deltafarms.com (Kenn E. Thompson) wrote in message news:<96aa2d22.04112...@posting.google.com>...

> Working on a Deutz Diesel engine. The instructions say to torque the
> bolts to 30 foot pounds then turn 45 degrees.
>
> Can I convert the degrees to foot pounds so I can use a torque wrench
> to make them more exact?
>

The turn-of-nut method sets a fixed stretch in the bolt, which gives a
fixed clamping pressure on the parts.

Depending on the design, the bolt is either acting like a spring, and:
modulus*(cross section)*stretch/(unstrained length of the stretched
section)
gives the clamping pressure

or it it being stretched to yeild and:
(yeild strength)*(cross section of yeild zone)
gives clamping pressure

In either case, the bolt should not be reused. If it is TTY, the next
time it is pulled in, the previously yeilded portion will have been
reduced in cross section and yeild at a lower tension. If not TTY, the
original tension is likely calculated to be 80% or more of yeild, and
there are likely high stress points that will yeild either as the bolt
is pulled in or during service.

The bolts are also quite likely to break, as the closer to the yeild
they are brought, the fewer fatigue cycles they can take, the obvious
limit being one cycle when they are stressed to the ultimate strength
the first pull (<--simplification to reduce volume of text)

The initial torque is principally to insure the parts are seated
properly before stretching the bolt. Since you arn't measuring the
actual stretch dirctly, there is no other easy way to insure that the
1/8 turn is used entirely for stretch, rather than some being wasted
to draw the parts together. The actual tension will be the sum of that
produced by the stretch of the bolt from the 1/8 turn and the tension
from the initial torque (which also strethes the bolt, and is likely a
minor part of the final tension)

There neatest tension setting setup I have worked with uses bolts
that have a small hole bored part-way up the axis with a pin slightly
longer than the hole depth inserted. As the bolt is tensioned, it
stretches, and when the pin is flush, the stretch, and therefore the
bolt tension, is correct.

Old Nick

unread,
Dec 1, 2004, 12:04:51 AM12/1/04
to
On 30 Nov 2004 19:29:53 -0800, dca...@krl.org (Dan Caster) vaguely

proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

>Now assuming this is less than yield, you can loosen it and retighten


>it over and over. No new bolt needed. You don't worry about flexing
>the springs in your car, do you. Stretching less than yield means it
>returns to the original length when the stress is removed.

This was my argument. But it would seem that in the real world, that
stretched bolt has been "damaged", or is assumed to be damaged.
Minimalism in engineering, heat, vibration etc.

Old Nick

unread,
Dec 1, 2004, 12:09:02 AM12/1/04
to
On 30 Nov 2004 20:57:09 -0800, enl_p...@yahoo.com (e) vaguely

proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

>webm...@deltafarms.com (Kenn E. Thompson) wrote in message news:<96aa2d22.04112...@posting.google.com>...


>> Working on a Deutz Diesel engine. The instructions say to torque the
>> bolts to 30 foot pounds then turn 45 degrees.
>>
>> Can I convert the degrees to foot pounds so I can use a torque wrench
>> to make them more exact?
>>
>
>The turn-of-nut method sets a fixed stretch in the bolt, which gives a
>fixed clamping pressure on the parts.
>
>Depending on the design, the bolt is either acting like a spring, and:
>modulus*(cross section)*stretch/(unstrained length of the stretched
>section)
>gives the clamping pressure
>
>or it it being stretched to yeild and:
>(yeild strength)*(cross section of yeild zone)
>gives clamping pressure

But surely if it's stretched to Yield (_and beyond_ if it's deformed),
then the clamping pressure will sart to drop straight away. Unless you
got _exactly_, and I mean _exactly_, Yield, you would not get (yeild
strength)*(cross section of yeild zone) but some lesser figure.

But I do have to admit,,,snip of very useful stuff after that. <G>

e

unread,
Dec 1, 2004, 11:34:06 AM12/1/04
to
Old Nick <nsnsa...@dodo.com.au> wrote in message news:<u8kqq01254jv8ok8s...@4ax.com>...


Amazingly, you just about do get exact clamping pressure. In fact, if
you don't go far into yeild, the pressure goes UP slightly as yeild
goes on a) because the yeild isn't an exact point, as the material
begins to stretch and neck, the stress goes up slightly, compensating
to a good extent for the reduced cross sectional area, and b) as the
material yeilds, it work hardens slightly, increasing the yeild stress
slightly. Ya, the effects are closely related. In practice, if it is
dead critical, a tool is used to detect yeild and stop there.

Don Bruder

unread,
Dec 1, 2004, 1:37:01 PM12/1/04
to
In article <96aa2d22.04112...@posting.google.com>,

webm...@deltafarms.com (Kenn E. Thompson) wrote:

> Working on a Deutz Diesel engine. The instructions say to torque the
> bolts to 30 foot pounds then turn 45 degrees.
>
> Can I convert the degrees to foot pounds so I can use a torque wrench
> to make them more exact?

There's no really practical way other than doing it as specified.
"Angle-to-torque" conversion would involve too many things that could be
variable - What's the pitch of the thread on the bolt? What's the
coefficient of friction for the material the bolt is made from? How
about for the material that the bolt is going into? What's the
shape/area of the bolt-head to fastened surface contact point, as well
as the CoF for that interface? How many tuyrns of thread are going to be
in the hole and meshed with the threads that are in the hole? Etc, etc,
etc... LOTS of "etc"s that add up to "You're better off doing it as the
instructions say."

Add in the fact that, as others have said, these are probably "stretch
bolts", intended to be cranked to a specific torque as a "reference
point", then cranked an extra 1/8th of a turn in order to put a
specified amount of stretch on them, and you're still ending up back at
"do it the way the instructions say."

Besides - 45 degrees = 1/8 of a turn - It's really not that difficult to
"eyeball" a well-within-reasonably-accurate approximation.

--
Don Bruder - dak...@sonic.net - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.

Old Nick

unread,
Dec 1, 2004, 5:20:32 PM12/1/04
to
On 1 Dec 2004 08:34:06 -0800, enl_p...@yahoo.com (e) vaguely

proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

hmmm...OK. If that is the way it's worked, then I can see why you
would not use the bolt again.

I couldn't see why you would want to go to, and beyond Yield, when you
would get an elastic stress there to clamp the joint, without needing
to wreck the bolt. But if there is a point when you can actually
maximise the clamp even aftger Yield then I can see the reason. As a
RAG (Rough As Guts) "engineer" I just use a bigger bolt! <G>

Thanks.

e

unread,
Dec 2, 2004, 10:01:38 PM12/2/04
to
Old Nick <nsnsa...@dodo.com.au> wrote in message
It isn't about getting the maximum clamping load, but about uniform
clamping load and gaurenteed clamping load. Even lubricated threads
lose a lot to friction, and a lot of the torque goes into twisting the
bolt rather than tensioning it, as much as 20 to 30 percent. TTY
provides a method, without the need for special equipment like strain
gauges, for providing predictable and uniform loading.

Even standard bolts generally shouldn't be reused in high stress
applications like an engine head because the properties change when
they are first torqued.

Typical designs for load-bearing bolts loaded in the elastic range are
50 to 80 percent of the yeild stress. All you get for using a bigger
bolt and not loading it to this high a stress is a bigger hole and a
more expensive bolt. Greater than 80 percent gets into the range where
unknowns in the installation process may bring the bolt into yeild.
Often not a good thing, as bolts not designed for this usually don't
have good yeild characteristics (they tend to yeild at the thread
root, where the minimum diameter is. bold designed for TTY usually are
reduced shank diameter)

news:<2ngsq0d554nntvd7p...@4ax.com>...

Tom

unread,
Dec 19, 2016, 1:18:03 PM12/19/16
to
replying to Dan Caster, Tom wrote:
How about if I'm using my old head bolt it's a nissan altima 2.5 liter it only
give me a 35 foot pounds then add 75 to 80 degrees

--
for full context, visit http://www.polytechforum.com/metalworking/convert-degrees-to-foot-pounds-379705-.htm


cl...@snyder.on.ca

unread,
Dec 19, 2016, 4:57:04 PM12/19/16
to
On Mon, 19 Dec 2016 18:18:02 +0000, Tom
<0f8503901d844703ee...@example.com> wrote:

>replying to Dan Caster, Tom wrote:
>How about if I'm using my old head bolt it's a nissan altima 2.5 liter it only
>give me a 35 foot pounds then add 75 to 80 degrees
Called torque to yield - AKA big expense as they are not to be
re-used - and they are not cheap. Also called "stretch bolts"

Jim Wilkins

unread,
Dec 19, 2016, 5:15:43 PM12/19/16
to
<cl...@snyder.on.ca> wrote in message
news:grlg5c186li06al5q...@4ax.com...
http://www.felpro-only.com/blog/proper-installation-use-t-t-y-bolts/


David Billington

unread,
Dec 19, 2016, 5:21:13 PM12/19/16
to
IIRC it depends on the design and what the makers say. The Rover K
series engine uses torque angle method and the bolts can be re-used a
few times provided the overall length doesn't exceed a specified length,
the design does use long bolts though that run from the top of the
engine through to the bottom ladder assembly which supports the
crankshaft. Price can be cheap I recall the FIAT twin cam used torque to
yield head bolts but they were quite cheap to get a set of them even
from the main dealer.

cl...@snyder.on.ca

unread,
Dec 19, 2016, 8:46:13 PM12/19/16
to
On Mon, 19 Dec 2016 22:21:10 +0000, David Billington <d...@invalid.com>
wrote:
The vast majority of TTY boltsm I encountered up untill about the
early nineties were single use bolts according to the factory manuals
at the time.

edhun...@gmail.com

unread,
Dec 19, 2016, 9:34:03 PM12/19/16
to
FWIW, the explanation on that site is not quite right. A bolt, or any piece of steel that has even a small amount of ductility, will continue to develop more stress (clamping force) well after its yield point is reached. It isn't practical to use that part of the curve for something like a head bolt for a couple of reasons, one of which is that different grades of steel can behave very differently after you pass the yield point.

What you get, with TTY bolts, is a reliably accurate and consistent clamping force, combined with a small amount of elasticity that will keep the clamping force very high even if the strain is somewhat relaxed, as when an engine cools down a bit after running hot.

But you can, as a technical issue, increase the clamping force by torquing beyond the yield point. It just isn't a practical thing to do in ordinary circumstances with normal bolts or studs.

--
Ed Huntress

Jim Wilkins

unread,
Dec 19, 2016, 9:58:21 PM12/19/16
to
<edhun...@gmail.com> wrote in message
news:3755f358-1088-4903...@googlegroups.com...
=========================
https://en.wikipedia.org/wiki/Stress%E2%80%93strain_curve



Tim Wescott

unread,
Dec 20, 2016, 1:00:27 PM12/20/16
to
Reuben Geissler, my across-the-road neighbor, when I was 14, advised me
that the way to find the correct torque on my 1948 Chevy head bolts was
to "torque them 'till they break, then back off half a turn". I see no
reason why that advise isn't just as valid today as it was then.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

edhun...@gmail.com

unread,
Dec 20, 2016, 1:10:07 PM12/20/16
to
Right. Depending on the alloy and the state of heat-treatment, most steels can be stressed quite a bit higher than the yield point, and they display more strength.

By that time, though, your threads commonly are going to hell. d8-)

--
Ed Huntress

Jim Wilkins

unread,
Dec 20, 2016, 1:39:55 PM12/20/16
to
<edhun...@gmail.com> wrote in message
news:296d0fe6-050d-4e08...@googlegroups.com...
The head bolts for my 1978 Honda Accord were so exotic looking that I
bought one to study. The shank was necked down smaller than the
threads and deeply roll-indented in a coarse spiral pattern, which I
think was to selectively work-harden the shank where it stretched
while the thicker threaded end didn't stretch enough to progressively
strip the threads in the block.

-jsw


edhun...@gmail.com

unread,
Dec 20, 2016, 2:25:00 PM12/20/16
to
Wow, that's pretty fancy. I've never seen those.

At Wasino, we turned test runs of big-end bolts for Cosworth engines. They were a bitch; we had to use custom PCBN inserts to turn the threads.

Anyway, they had a *much* thinner shank, possibly because the threads were a weak point. The more accurate way to describe it may be that the threaded portion was intentionally oversize.

--
Ed Huntress

Larry Jaques

unread,
Dec 20, 2016, 3:22:15 PM12/20/16
to
What do you give the odds of the replacements being installed
correctly or the originals being reused? I've never seen TTY bolts,
but I got out of the biz in '85. It's been a while.

I have, however, seen plenty of people who used a torque wrench
improperly, trying to speed up the act of torquing bolts down. It
_always_ resulted in too little torque being applied to the head- or
main-bolts, sometimes with disastrous results.

--
...in order that a man may be happy, it is
necessary that he should not only be capable
of his work, but a good judge of his work.
-- John Ruskin

Larry Jaques

unread,
Dec 20, 2016, 6:15:44 PM12/20/16
to
On Tue, 20 Dec 2016 12:00:20 -0600, Tim Wescott <t...@seemywebsite.com>
wrote:

>Reuben Geissler, my across-the-road neighbor, when I was 14, advised me
>that the way to find the correct torque on my 1948 Chevy head bolts was
>to "torque them 'till they break, then back off half a turn". I see no
>reason why that advise isn't just as valid today as it was then.

I've always -loved- that one. LOL!
"Tighten it until it snaps, then _quickly_ back if off half a turn."

cl...@snyder.on.ca

unread,
Dec 20, 2016, 8:19:32 PM12/20/16
to
The only time I tried to re-use TTY headbolts I had to replace them
a few months later and it cost me a head gasket. When they break, you
can'y easily remove them without pulling the head. They may have been
compromised by not being properly torqued before, Undertorqued, they
fatigue from stretching and relaxing with every heaty cycle. Properly
totqued they basically don't move.

Larry Jaques

unread,
Dec 21, 2016, 10:57:02 AM12/21/16
to
On Tue, 20 Dec 2016 20:19:31 -0500, cl...@snyder.on.ca wrote:
I said:
>>> The vast majority of TTY boltsm I encountered up untill about the
>>>early nineties were single use bolts according to the factory manuals
>>>at the time.
>>
>>What do you give the odds of the replacements being installed
>>correctly or the originals being reused? I've never seen TTY bolts,
>>but I got out of the biz in '85. It's been a while.
>>
>>I have, however, seen plenty of people who used a torque wrench
>>improperly, trying to speed up the act of torquing bolts down. It
>>_always_ resulted in too little torque being applied to the head- or
>>main-bolts, sometimes with disastrous results.
> The only time I tried to re-use TTY headbolts I had to replace them
>a few months later and it cost me a head gasket. When they break, you
>can'y easily remove them without pulling the head.

Ooh, bummer. Did you not know about their being TTY? Total cost was a
set of bolts, another head gasket, and another gasket job. Both time-
consuming and costly, right? Ouch.


>They may have been
>compromised by not being properly torqued before, Undertorqued, they
>fatigue from stretching and relaxing with every heaty cycle. Properly
>totqued they basically don't move.

UTI was a long time ago, but I don't recall ever hearing that an
undertorqued bolt fatigued from stretching like that. I may never have
learned about it.

Volkswagons are the leader when it comes to massive stretching of the
head bolts. I've heard them going down the street, the heads bopping
up and down on the cylinders. It heightens my disdain for the ugly,
hissing beasties. The Cherman engineers should be shot for the noise +
harmonics the engine and muffler produce. Give me fingernails on a
chalkboard any day, over that monstrosity. Thankfully, the new Bug
engines are all but silent.

Jim Wilkins

unread,
Dec 21, 2016, 1:15:02 PM12/21/16
to
"Larry Jaques" <lja...@invalid.diversifycomm.com> wrote in message
news:kq6l5cl6qhbhfmcug...@4ax.com...
I bought two $300 high-mileage Beetles which were pretty quiet after I
adjusted the valves.

This morning I addressed two other issues that might be of interest. I
bought a used 120VAC starter to fit the Tecumseh HSK70 engine on my
20-year-old Toro 724 snowthrower. Running a 1/4-20 bottoming tap into
the mounting holes in the block cut two more turns and let them accept
1/2" long screws. I've seen the shallow holes strip, possibly from
using 3/8" screws.

I use Dell D820 laptops running Win7 as portable TVs and digital
recorders. On one the screen started intermittently blanking which
turned out to be triggered by the lid-closed switch, a magnet in the
lid by the latch and sensor in front of the right touchscreen button.
You can find the magnet with a paper clip. Holding a magnet over the
sensor blanks the screen even if Do Nothing is set in Power Options.
Apparently this is an APCI Lid driver bug in Vista, Win7 and maybe 10.
The suggested fix is to replace (disable) it with the Volume Manager
driver, which seems to work so far. Swiping a magnet over the sensor
to simulate closing the lid still blanks the screen.
http://www.techsupportforum.com/forums/f217/solved-laptop-lid-problem-164329.html

--jsw


Larry Jaques

unread,
Dec 22, 2016, 12:05:01 AM12/22/16
to
"Hmmm..." he distrusted. ;)


>This morning I addressed two other issues that might be of interest. I
>bought a used 120VAC starter to fit the Tecumseh HSK70 engine on my
>20-year-old Toro 724 snowthrower. Running a 1/4-20 bottoming tap into
>the mounting holes in the block cut two more turns and let them accept
>1/2" long screws. I've seen the shallow holes strip, possibly from
>using 3/8" screws.

Ooh, that could be a lifesaver for many owners and repairmen.


>I use Dell D820 laptops running Win7 as portable TVs

Whatever _for_?


>and digital
>recorders. On one the screen started intermittently blanking which
>turned out to be triggered by the lid-closed switch, a magnet in the
>lid by the latch and sensor in front of the right touchscreen button.
>You can find the magnet with a paper clip. Holding a magnet over the
>sensor blanks the screen even if Do Nothing is set in Power Options.
>Apparently this is an APCI Lid driver bug in Vista, Win7 and maybe 10.
>The suggested fix is to replace (disable) it with the Volume Manager
>driver, which seems to work so far. Swiping a magnet over the sensor
>to simulate closing the lid still blanks the screen.
>http://www.techsupportforum.com/forums/f217/solved-laptop-lid-problem-164329.html


Only in a Mickeysoft product would it be possible for an audio program
to control the magnetic screen driver.

Jim Wilkins

unread,
Dec 22, 2016, 8:16:01 AM12/22/16
to
"Larry Jaques" <lja...@invalid.diversifycomm.com> wrote in message
news:binm5clf205jl8pbp...@4ax.com...
> On Wed, 21 Dec 2016 13:15:49 -0500, "Jim Wilkins"
> <murat...@gmail.com> wrote:
>

>>I use Dell D820 laptops running Win7 as portable TVs
>
> Whatever _for_?

Don't expect me to validate your personal peculiarities.

I record mostly the morning, noon and evening weather reports instead
of trying to remember them, because I need to plan my outdoor work and
line-dried laundry for dry days and save indoor jobs for bad weather
like this morning. The local radio is useless for weather and
http://radar.weather.gov shows when it's time to stop and cover up
because <something> is about to hit, but not what it is, or the track
and timing of distant storms. I don't pay for either cable TV or a
smart phone plan.

PBS still runs concerts and some fairly decent science and history
material and the commercial networks have been presenting live
performances of Broadway shows featuring some of the
Kelly/Astaire-class talent that Dancing With the Stars has attracted.
I can't defend the rest of their programming.
http://www.justjaredjr.com/2016/11/09/mark-ballas-reunites-with-derek-hough-brings-jersey-boys-to-dwts/
Derek's sister:
https://www.youtube.com/watch?v=iHJNpG2kRxc

>>and digital
>>recorders. On one the screen started intermittently blanking which
>>turned out to be triggered by the lid-closed switch, a magnet in the
>>lid by the latch and sensor in front of the right touchscreen
>>button.
>>You can find the magnet with a paper clip. Holding a magnet over the
>>sensor blanks the screen even if Do Nothing is set in Power Options.
>>Apparently this is an APCI Lid driver bug in Vista, Win7 and maybe
>>10.
>>The suggested fix is to replace (disable) it with the Volume Manager
>>driver, which seems to work so far. Swiping a magnet over the sensor
>>to simulate closing the lid still blanks the screen.
>>http://www.techsupportforum.com/forums/f217/solved-laptop-lid-problem-164329.html
>
>
> Only in a Mickeysoft product would it be possible for an audio
> program
> to control the magnetic screen driver.

The point is that they allow you to install a driver that occupies the
space but doesn't do -anything-, good or bad.

--jsw


normangoo...@gmail.com

unread,
Jun 6, 2017, 12:32:47 AM6/6/17
to
30

Good Guy

unread,
Jun 6, 2017, 3:28:24 AM6/6/17
to
On 06/05/2017 09:32 PM, normangoo...@gmail.com wrote:
> 30
>

273.15K - 40C = -40F

Good Guy

unread,
Jun 6, 2017, 3:40:45 AM6/6/17
to
so that doesn't even take into account the thread pitch. you might
advance 1 inch per turn. imagine that.

Peter Jason

unread,
Jun 6, 2017, 5:54:49 PM6/6/17
to
On Tue, 6 Jun 2017 00:28:18 -0700, Good Guy <Hello....@example.com>
wrote:

>On 06/05/2017 09:32 PM, normangoo...@gmail.com wrote:
>> 30
>>
>
>273.15K - 40C = -40F


Don't you mean Kelvin?

There are aps for your mobile for this sort of thing.

Keith Nuttle

unread,
Jun 6, 2017, 8:26:30 PM6/6/17
to
On 6/6/2017 5:54 PM, Peter Jason wrote:
> :28:18 -0700, Good Guy<Hello....@example.com>
> wrote:

Unless I miss understand your use of terms, it can not be done.
Degrees is a temperature measurement, OR a part of a circle.

Foot pounds is a measure of force.


If you are thinking foot pounds as the number of degrees that you must
turn a nut, it depends on the wrench being used.

There is a rule of thumb that when you tighten a nut, you should turn
it as tight as possible and then back off by an 1/8 of a turn. That
sort of encompass the terms you used in your questions

--
2017: The year we lean to play the great game of Euchre

Smooth Guy

unread,
Jun 6, 2017, 11:36:55 PM6/6/17
to
Peter Jason wrote:
> Good Guy <Hello....@example.com> wrote:
>> normangoo...@gmail.com wrote:
>>> 30
>>>
>>273.15K - 40C = -40F
>
> Don't you mean Kelvin?

Kelvin is in there.

Terry Coombs

unread,
Jun 7, 2017, 2:27:49 PM6/7/17
to
Not up on modern engines are you ? Head bolts on almost everything
out there now has a torquing sequence where the last step is to turn the
bolt a specified number of degrees . It's called "stretch to torque" .
Even my antique (officially ! it's a 1990) Harley has that type of
cylinder studs .

--

Snag

Bob Engelhardt

unread,
Jun 7, 2017, 2:28:37 PM6/7/17