How to determine the spec of a pinion gear wheel

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How to determine the spec of a pinion gear wheel

This topic has 11 replies, 8 voices, and was last updated 27 October 2015 at 08:43 by Michael Gilligan.

Viewing 12 posts - 1 through 12 (of 12 total)

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25 October 2015 at 10:06 #7836
Steve Withnell
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@stevewithnell34426
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25 October 2015 at 10:06 #209169
Steve Withnell
Participant
@stevewithnell34426
I managed to destroy my paper shredder yesterday, it wasn't man enough to eat a bank book…the pinion on the motor shaft disintegrated.

It will be really difficult/impossible to buy a new one, but should be easy to make one – it's about 15 straight teeth and about 1/2 inch overall diameter.

If I stick all the bits back together so I can measure it properly, how do I determine if it's Module or spec'd in DP and then measure the key characteristics? I think I can count the number of teeth, pretty accurately

Fingers crossed it might just drop in with the job lot of cutters I bought a couple of years ago.

Steve
25 October 2015 at 10:16 #209173
Michael Gilligan
Participant
@michaelgilligan61133
Steve,

Count the teeth, and add two

Measure the Outside Diameter, in inches

DP is one over t'other

If it doesn't compute to nice number, try converting to Module.

… Sorry: of out now, more tonight if someone hasn't already explained it better.

MichaelG.
25 October 2015 at 13:39 #209195
Roderick Jenkins
Participant
@roderickjenkins93242
As MG says. Metric module is 25.4 divided by DP.

Rod
25 October 2015 at 13:45 #209197
JasonB
Moderator
@jasonb
Unlikely to be DP, more likely MOD

15T 0.75Mod is 12.75mm OD which is "about 1/2" "

Edited By JasonB on 25/10/2015 13:46:09
25 October 2015 at 14:20 #209200
John Stevenson 1
Participant
@johnstevenson1
Very close to 32DP which will be good enough for a paper shredder.
25 October 2015 at 16:50 #209225
duncan webster 1
Participant
@duncanwebster1
HPC list 15t 0.75 module, for about £10. I daresay if you send them the bits they will advise
26 October 2015 at 10:06 #209291
Gordon W
Participant
@gordonw
Unless you really want to make a gear wheel just buy a new one, shredder that is. Strip the old one for useful bits. Mine 's just gone in sympathy with you.
26 October 2015 at 17:59 #209361
Steve Withnell
Participant
@stevewithnell34426
Looks like I can neither measure nor count…

I took a look at the HPC catalogue and tried to match it to their gears, best fit is Module 2, 24mm(!) and 9 teeth (!!)

When I look at cutter numbers, stock cutters only go down to 12-13 teeth – so 9 teeth sounds like not that easy at all – or is there a trick? Otherwise it's a salvage project, rather than a repair.

Steve

Edited By Steve Withnell on 26/10/2015 18:00:25
26 October 2015 at 18:11 #209363
Neil Wyatt
Moderator
@neilwyatt
Work out the DP/mod from the gear it meshes with, it will be bigger with more teeth and therefore easier to measure accurately, also the larger gear is less likely to have a modified profile.

> so 9 teeth sounds like not that easy at all – or is there a trick?

Yes, file up a single point cutter to be a good fit in between two teeth of the broken gear, and cut about 4-5 thou deep.

Neil
26 October 2015 at 20:18 #209385
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Steve Withnell on 25/10/2015 10:06:43:

– it's about 15 straight teeth and about 1/2 inch overall diameter.

If I stick all the bits back together so I can measure it properly …

.

Steve,

Going back to your opening post ^^^

If you have put enough of the bits together … please take a photo, or put it on a flatbed scanner, so that we can see.

Based on your original figures of 15 teeth and 1/2" OD …

17/0.5 = 34 DP … but pinions are often cut 'wrong' to get the working clearance: My guess is that the matching gear will be 32 DP, or Module 0.8

MichaelG.
27 October 2015 at 08:43 #209423
Michael Gilligan
Participant
@michaelgilligan61133
… of course; if it is really 24mm OD and has 9 teeth, you can safely ignore my last night's calculation !!

MichaelG.
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