waxy plastic gear repair

[Splork]

My low tech pencil sharpener has a drive that uses a 2.2" gear to drive the
mechanism from the motor. The gear broke into 3 pieces.

I can probably repair it but am unsure of the composition and what to use for
cement/ strengthening.

It is an Amber waxy looking/feeling material and it scrapes like wax.

What is this??

TIA

[isw]

In article <ltvo88ln7d3pf3c8u...@4ax.com>,

Splork <spl...@splork.net> wrote:

> My low tech pencil sharpener has a drive that uses a 2.2" gear to drive the
> mechanism from the motor. The gear broke into 3 pieces.
>
> I can probably repair it but am unsure of the composition and what to use for
> cement/ strengthening.

Cut a groove around the perimeter, deep enough to get past the gear
teeth. Wrap a steel wire around the gear in the groove, and twist the
ends to make it tight. If cyanoacrylate will stick to the plastic, use
that to get the pieces assembled before you add the wire.

Isaac

[Jeff Liebermann]

My guess(tm) would be Molybdenum disulfide lubricated nylon gears.
Search google for "self lubricating plastic gears".

However, glue is not going to help. No glue will stick to a plastic
gear that is impregnated with some manner of wax or grease. Your best
bet is to temporarily stick the gear together with some manner of
cyanoacrylate adhesive (super glue), and make a lost wax plaster mold
in order to clone the gear.
<http://en.wikipedia.org/wiki/Lost-wax_casting>

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[N_Cook]

isw <i...@witzend.com> wrote in message
news:isw-66F96C.22243727102012@[216.168.3.50]...

Are you saying cut a slot through the middle of the teeth into the bulk
under the teeth?
I suspect a .4mm saw in a Dremmel would end up as a melted mess and not a
slot, perhaps a heated scalpel blade in a jig

Or perhaps use some nicrome wire with some silone sleeve at the overlap,
apply a weight and some adjustable current. Hope the wire melts into the
bulk of the plastic and perhaps ypu can ignore twisting off of the wire.
May need to recess 3 pins into the disc part , then swathe in hotmelt or
something, if the 3 sections have failed with smooth edges, before doing the
wire job

[N_Cook]

N_Cook <div...@tcp.co.uk> wrote in message
news:k6lgs3$7bm$1...@dont-email.me...

on second thoughts as its 2.2 inch there is probably quite a thickness of
bulk material. Wire and twist around the teeth to act as an alignment jig ,
then 3 pins and generally hotmelt "soldering" along all the joins, cut away
the wire.
Precede with a test that the plastic and hotmelt are compatible in the first
place.

[William Sommerwerck]

The Lady from Philadelphia advises you to purchase a new pencil-sharpening
instrument.

[N_Cook]

William Sommerwerck <grizzle...@comcast.net> wrote in message
news:k6lt4o$do3$1...@dont-email.me...

> The Lady from Philadelphia advises you to purchase a new pencil-sharpening
> instrument.
>
>

You've just posted that 'reply' to a thread with repair in the title on a
board with repair in the title

[Jamie]

what is a waxy plastic gear? I can't picture any gears being made of wax
or material soft like wax?

Jamie

[N_Cook]

Jamie <jamie_ka1lpa_not_v...@charter.net> wrote in message
news:erwjs.3940$WP2....@newsfe20.iad...

I've come across them but don't remember where, glossy looking as though
covered in oil , hard white material but not PTFE , and slippery to the
touch but no oil film. IIRC quite coarse teeth and pitch as though not very
structural plastic.

[hr(bob) hofmann@att.net]

On Oct 29, 7:42 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> William Sommerwerck <grizzledgee...@comcast.net> wrote in message

But common sense has a place even in a repair group.

[William Sommerwerck]

> You've just posted that "reply" to a thread with repair in the title

> on a board with repair in the title.

You're rather missing the point.

The reference is to a character in Lucretia Peabody Hale's short stories
"The Peterkin Papers". Said lady was a fountain of common sense, giving
simple solutions to what appeared -- to the Peterkins -- to be complicated
problems.

http://en.wikipedia.org/wiki/The_Peterkin_Papers

[isw]

In article <k6lgs3$7bm$1...@dont-email.me>, "N_Cook" <div...@tcp.co.uk>
wrote:

> isw <i...@witzend.com> wrote in message
> news:isw-66F96C.22243727102012@[216.168.3.50]...
> > In article <ltvo88ln7d3pf3c8u...@4ax.com>,
> > Splork <spl...@splork.net> wrote:
> >
> > > My low tech pencil sharpener has a drive that uses a 2.2" gear to drive
> the
> > > mechanism from the motor. The gear broke into 3 pieces.
> > >
> > > I can probably repair it but am unsure of the composition and what to
> use for
> > > cement/ strengthening.
> >
> > Cut a groove around the perimeter, deep enough to get past the gear
> > teeth. Wrap a steel wire around the gear in the groove, and twist the
> > ends to make it tight. If cyanoacrylate will stick to the plastic, use
> > that to get the pieces assembled before you add the wire.
> >
> > Isaac
>
> Are you saying cut a slot through the middle of the teeth into the bulk
> under the teeth?

Yup. Exactly.

> I suspect a .4mm saw in a Dremmel would end up as a melted mess and not a
> slot, perhaps a heated scalpel blade in a jig

Just use a coping saw.

> Or perhaps use some nicrome wire with some silone sleeve at the overlap,
> apply a weight and some adjustable current. Hope the wire melts into the
> bulk of the plastic and perhaps ypu can ignore twisting off of the wire.
> May need to recess 3 pins into the disc part , then swathe in hotmelt or
> something, if the 3 sections have failed with smooth edges, before doing the
> wire job

Something to hold it together long enough to get the groove cut would
make it easier. Even clamping the pieces between a couple of washers
might do it.

Isaac

[Splork]

Thanks to all the replies!!

The unit is at least 20 years old.

The gear is brown Bakelite in color. I say waxy because it has a soapy feel and
I can scrape the material with my thumbnail and get some to come off. Like very
hard wax. Odd for a drive gear material so I suppose it changed in nature over
time. The exterior seems most changed so perhaps there is some material
strength remaining.

The teeth are about twice as wide as the body and none have broken off. A clean
3 way break. The body is too thin for making a groove around the perimeter.

Adhesive would be required in and around the breaks for adequate strength.

I cannot think of an adhesive for this material so I posted here hoping for
anyone familiar with it to chime in.

As an alternate to a lost wax reproduction, I thought of reassembling the gear
and wiring it to stay put, some holes could be drilled through the disc (several
on each segment) and a 2 operation repair then be undertaken. On one side a
layer of JB Weld between hub and teeth, then a repeat on the other side. Would
give a metal sandwich with the holes ensuring the teeth remain in roper position
and are driven. Will look over the unit to see if any special clearance need be
observed. Likely the best option in hand.

Just discovered someone who has cloned the gear and is selling them $12 or so.

[Jamie]

They call it micarta
http://en.wikipedia.org/wiki/Micarta

Jamie

[N_Cook]

Jamie <jamie_ka1lpa_not_v...@charter.net> wrote in message

news:4kjls.17182$Be....@newsfe13.iad...

In that case, known as Tufnol in the UK . But as those are cloth reinforced
I would not have expected the material to split , has it got fibrous mat
reinforcement?

[N_Cook]

Jamie <jamie_ka1lpa_not_v...@charter.net> wrote in message
news:4kjls.17182$Be....@newsfe13.iad...

I suspect its this material , upper left cog but I don't know what its
called
http://www.rennbay.com/pics/928installgear/Fig.%2050.jpg
from
http://www.rennbay.com/odotutorial.html
structurally poor but decouples vibration from a gear train

[Jamie]

Micarta is the trade name for the company that created the process. I
guess you can use a wide range of material to make it, you need to be
specific in its use, which dictates the composites better suited for the
jobs.

People that make knife handles could use micarta composite and what
they mostly do is use layers to clothe soaked in a resin and compressed
in a bundle until hardened...

I've seen them use all sorts of different materials over the years,
including hemp.

Jamie

[Arfa Daily]

"Splork" <spl...@splork.net> wrote in message
news:ltvo88ln7d3pf3c8u...@4ax.com...

Knackered, I'd say ...

Arfa

[Splork]

Color looks about right. Will get a scan of it tomorrow and post it. I saw a
number of posts on web sites referring to odometer repair while looking for info
on this gear. Also found a site where there are dozens of people with this same
problem asking for some reason: My post "Boston Model 18 Lg Gear Needed"

http://www.merchantcircle.com/business/Hunt.Manufacturing.Co.704-871-0941/shoutout/list

There is no binder or substrate to it. Heft in the teeth and hub, body half as
thick.

I see that the center hole of the hub which is keyed to the drive shaft may have
worn a bit allowing the shaft some slack and instead of all force delivered to
driving the gear, some was directed against small points on the hub surface.
The drive has a 15 degree or so pitch and this slack would allow the gear motion
off axis which would also work to crack it.

A little slop may be what killed it.

If I go with a JB Weld repair I will grease the shaft and use JB weld on the hub
also.

Thanks to all for the conversation.

[William Sommerwerck]

> Micarta is the trade name for the company that created the process.

The original micarta was developed by George Westinghouse. As a laminate,
Westinghouse sold it well into the 1960s. GE had a similar product,
textolite, which was used for countertops, gears, etc. Both are similar to
Formica.

[et...@whidbey.com]

Micarta is also know generically as "Phenolic". However, phenolic does
not always mean it is made with phenolic resin. The first Micarta was
made with Bakelite, a phenolic resin, but for years now a very common
phenolic is G10, which every one here would recognize as fiberglass
filled epoxy circuit board material. I have machined several different
types of phenolic over the years, linen filled, fiberglass filled,
carbon fiber filled, paper filled. etc. G10 is quite strong and is
easy to glue with epoxy if the surface is roughed up a bit first.
Eric

[Jamie]

G11 is better, stronger! FR5

Jamie

[Splork]

On Sun, 4 Nov 2012 09:00:35 -0000, "N_Cook" <div...@tcp.co.uk> wrote:

Here are 2 scans. One lighter to show some detail, the other both sides, one
which easily reassembles.

I think JB weld must might do a good job after each piece has a couple of holes
to the other side to form a clamp.

http://users.rcn.com/healer//Gear1.jpg
http://users.rcn.com/healer//Gear1a.jpg

[Splork]

On Wed, 07 Nov 2012 08:22:31 +0000, Charlie+ <cha...@xxx.net> wrote:

>On Tue, 06 Nov 2012 22:57:02 -0500, Splork <spl...@splork.net> wrote as
>underneath my scribble :
>
>Crack on the left is the original, the gear has been running eccentric
>some time, wear on the right teeth is considerable, if you do a repair
>pay considerable attention to concentric-icity(!!) to the centre. Is
>the equipment worth it? A dirty repair might be to use hot glue for
>thin metal or fibre washers in the rebates... try first to see if hot
>glue will stick to the soft gear material, might have to abrade.
>>
>>http://users.rcn.com/healer//Gear1.jpg
>>http://users.rcn.com/healer//Gear1a.jpg


That's the word I was looking for yesterday. Concentric.

This is a pencil sharpener.
When I reach to use it and it is gone . . . Yeah, worth it.

The only repair that I think worthwhile, which is potentially long lasting, is
on each piece, to place 2 holes halfway between hub and teeth, 3 holes on the
largest, to allow jb weld (Strong metal bearing epoxy) to join obverse and
reverse of the gear (2 operations). Once sandwiched between the "weld", being
restrained and driven by the pins that form through the holes, I can place the
gear on the drive shaft and greasing the gear end to prevent adhesion, make a
third gluing operation for a strong tight fit around the shaft end.

So the cracks will not be repaired, but the pins/vias that form in the holes
will keep it together, sandwiched between plates which prevent it from
divergence in any axis. The 3 segments held and driven separately.

Now if laziness prevails........ :-)

[N_Cook]

Charlie+ <cha...@xxx.net> wrote in message
news:j9lm98laptdjp6m71...@4ax.com...
> On Wed, 07 Nov 2012 20:49:51 -0500, Splork <spl...@splork.net> wrote as

> Good luck with it, hot glue has some 'give' in it which would provide
> the required flexibility.


What I call hotmelt string is more convenient in this sort of operation.
With the gun hot, squeeze out a long run of hotmelt over clean metal sheet.
When cold , use like soldering operation with an old soldering iron, melding
original material and the string.

[Splork]

Thanks for the suggestions. Sounds interesting to me. Never used hot glue so I
find the use of it like solder intriguing, and I like cleverness.

Perhaps I am over estimating my need for strength. Rarely successful at
repairing plastic gears and one of this size seems an unlikely candidate for
glue. I do have a glue gun here somewhere.

There is a lot of force applied to the shaft via the hub. Lots of torque needed
to turn the sharpener blades. Manually un-movable.

Will probably use the idea I had using JBWeld to create the least amount of
give, but will experiment with hot glue to experience it's usefulness, and use
it when I attempt small plastic gear replacement.

Good stuff!

Thanks again

[Leif Neland]

Splork udtrykte præcist:

> My low tech pencil sharpener has a drive that uses a 2.2" gear to drive the
> mechanism from the motor. The gear broke into 3 pieces.
>
> I can probably repair it but am unsure of the composition and what to use for
> cement/ strengthening.
>

> It is an Amber waxy looking/feeling material and it scrapes like wax.
>

Perhaps you can find somebody with a 3D-printer who will print a new
gear?

Somebody who has made their own 3D-printer might be looking for
interesting stuff to print.

But then again, get a new one, unless you have lot of free time and no
money.

Leif

--
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