involute gears 1

[urkson]

I am in the process of inspecting some 1st articles. I am not that familiar with gear design but the gear spec on one of the prints I have doesnt seem right.I have a pitch diameter of 2.0625 on a gear that has 72 teeth and then a diametral pitch callout of 32. I thought the diametral pitch was calculated by dividing the pitch dia by the number of teeth. Now in the gear spec on the print for the mating part there is no diametral pitch callout but there is a circular pitch callout of 32 on a pitch dia of 2.250. Maybe this is correct and my limited knowledge is getting in the way.

Thanks.

 

[gearcutter]

Both specs are incorrect in some way.
You are correct - standard PD = Z / DP.
There's no such thing as 32CP.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[urkson]

I have detailed below the two gear specs I am dealing with if you see any other errors can you please explain them.

Thanks

1. DIAMETRAL PITCH: 32
2. PRESSURE ANGLE = 20.0DEG
3. NUMBER OF TEETH: 32/66
4. PITCH DIAMETER: 1.000/2.0625
5. OUTSIDE DIAMETER: 1.0625/2.125
6. TOOTH DESIGN: INVOLUTE CURVE
7. QUALITY CLASS: AGMA Q10

1. PITCH DIAMETER = 2.250
2. OUTSIDE DIAMETER = 2.312
3. PRESSURE ANGLE = 20.0DEG
4. N = 72 TEETH ON FULL CIRCLE
5. N= 25 TEETH ON SECTION
6. CIRCULAR PITCH = 32
7. TOOTH DESIGN = INVOLUTE CURVE
8. AGMS = CLASS 76

 

[urkson]

I should add that the first gear spec is a compound gear hence the dual values.

 

[Occupant]

So, somebody made a mistake with the second gear - item 6. no such thing.

 

[urkson]

I am trying to make sense of the Diametral Pitch callout on the first gear. Dividing the Pitch Dia.(2.0625) by number of teeth(66) you get .031. Is this translated as a value of 31. This would make sense to the callout of 32. If that is the case perhaps in the spec for the second gear the designer meant diametral pitch of 32 not circular pitch.

Forgive me for my lack of knowledge on the subject but the designer is no longer with our company and there is no body else here who understands gears.

 

[Occupant]

Dividing the Pitch Dia. by the number of teeth gets you the inverse of the Diametral Pitch - and what do you want to do with that?

 

[dinjin]

Z/dp yields 66/32 and 32/32 yields the 2.0625 and 1.000 pitch diameters.

72/32 yields the 2.500 pitch diameter.
25/32 yields .78125 pitch diameter.

 

[tbuelna]

The gear data shown in the second post seems to agree with standard 32DP gear dimensions. Pitch diameter = no. of teeth / diametral pitch . Outside diameter = (no. of teeth + 2) / diametral pitch .

The only exception is the value shown for circular pitch. circular pitch = Pi / diametral pitch .