Measuring the pressure angle of gears

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Measuring the pressure angle of gears

This topic has 7 replies, 6 voices, and was last updated 8 September 2010 at 21:14 by Robert Miller 1.

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7 September 2010 at 13:31 #55242
Michael Cox 1
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@michaelcox1
Does anyone have any ideas about measuring the pressure angle of gears?

I have tried measuring the curvature of gear teeth form photos taken with a camera and with a USB microscope and then using Ivan law’s circular approximation to estimate the pressure angle. However, I am getting very inconsistent results. Any other ideas?

Mike
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7 September 2010 at 13:31 #15479
Michael Cox 1
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@michaelcox1
7 September 2010 at 14:31 #55246
Joseph Ramon
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@josephramon28170
Flatten out a blob of blu-tac or plasticine on the bench.

Roll the gear over the top to leave the impression of a rack.

In principle it should leave a straight-sided impression the angle of the sides being the pressure angle.

In practice it won’t be perfect, especially if the gears are small, but it should distinguish different angles.

Joey
7 September 2010 at 16:27 #55250
JasonB
Moderator
@jasonb
Download the file Gearpa.zip from tthis page and you should be able to measure your gears, Marv’s got a lot of useful little programmes there.

Jason
8 September 2010 at 09:36 #55300
Gordon W
Participant
@gordonw
Last time I did this was about 30 yrs ago, and a big gear, 2 ft. dia and 13 teeth, but might help. Trace tooth on paper and measure angle. From the physical dims of the gear, and assuming yours is a standard pressure angle, with the help of the tables, should be able to be fairly sure. Not well explaiined but might help.
8 September 2010 at 11:10 #55305
Michael Cox 1
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@michaelcox1
Thanks for all the ideas.

I had tried some of these ideas.

The plasticine method sounds easy in principle but the gear I have been trying to measure is a MOD 1 plastic 30 tooth change gear for a minilathe. This is small and the plasticine tends to stick between the teeth.

The Gearpa.zip method also gave difficulties because differences were two small to measure reliably.

Gordons idea would certainly work on a large gear but is more difficult for small gears.

I have now convinced myself that the gear has a pressure angle of 20 degrees using the method described here:

http://mikesworkshop.weebly.com/change-gear-pressure-angle.html

Mike
8 September 2010 at 21:03 #55346
Sub Mandrel
Participant
@submandrel
The minilathe change gears are20 degrees. pm me your email and I’ll send you some stuff about how to cut your own mini lathe gears with minimal equipment. Also see my photo album.

Neil
8 September 2010 at 21:14 #55347
Robert Miller 1
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@robertmiller1
There is a description of how to do this in Huston Tx’s home metal shop club’s latest newsletter at:

http://www.homemetalshopclub.org/news/10/newsletter1008.pdf#Page=8&view=fitH
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