PA From a Pic?

G-ManBart

G-ManBart

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I'm thinking about making a set of metric change gears for my Sheldon lathe and I'm not sure what PA they used. Sheldon used both 14.5 and 20 over time, so it could easily be either. I've read people say they can look at one and tell immediately.. I know what it looks like to me, but I'm an amateur, so what do you think? This is a 100 tooth 16DP gear.

A set of gauges in both 14.5 and 20 PA are on my short list of purchases.

IMG_3268.JPG
 
Boston gear catalogue is to scale as well. Maybe you can display this at 1:1 and compare?

C65431C5-48B3-490E-8B10-ED69C0ACC59A.jpeg
 
Last edited:
pdentrem said:
Boston gear catalogue is to scale as well. Maybe you can display this at 1:1 and compare?
Click to expand...
I looked there yesterday and couldn't find a 16DP gear with 100 teeth (also checked 44 as that one engages the 100) in 20PA for some reason.

I used the picture you provided (thanks!) and while I couldn't get it to print to scale, putting it next to the gear tells me it's likely 20PA, which is what I was already guessing.

This isn't a rush project, I was just trying to do some research on involute cutter sets, etc. I can always wait until l get a gauge to be 100% certain....at least this way I can buy the 20PA set first. If it's 14 1/2 I'm sure it will be obvious.
 
Good.
Boston had 100 16DP in the change gear section of their catalogs.
 
3d print a gear?
Buy a known PA gear?
Scan, blow up, draw in the pitch circle, measure the flank angle?

Sent from my SM-G715A using Tapatalk
 
pdentrem said:
Good.
Boston had 100 16DP in the change gear section of their catalogs.
Click to expand...
The only 16DP 100T gear I found in the change gear section was 14 1/2PA....guess I could have tried to print that and if it didn't match, would confirm it as 20PA. I'm a bit under the weather and didn't think of that!
 
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