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# Question about AGMA standard

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## Question about AGMA standard

(OP)
hello
i'm sizing a couple of helical gears and i have a question about this image: . N are about number of teeth and P_d is transverse diametral pitch
i don't think it is correct because the result is too little. I think the correct formula is C=(D+d)/2, with "d and D" pitch diameters.

the second question is about the word "manufactured". in the handbook there is the distinction between "manufactured center distance C" and "operating center distance C_o". i don't have any info about C_o, neither in the handbook. how can i assess it?

### RE: Question about AGMA standard

Hello,

i don't have the respective AGMA paper in my hand, but imo the above formulas would be correct if Pd was proportional to 1/modulus. So looking up in wikipedia i found:

So prhaps there's again a metric vs. imperial "mantrap", hopefully you don't design spaceships to Mars?...
For the other question, there must be a formula somewhere, else there's no sense t make up the difference. Also, there's a thread here on eng-tips: http://www.eng-tips.com/viewthread.cfm?qid=146377.

Regards

Roland Heilmann
Lpz FRG

### RE: Question about AGMA standard

I think, you read that wrong. Since it is a capital "P", it means diametral pitch and not circular pitch.

### RE: Question about AGMA standard

Can you provide the AGMA spec number the equations came from? I took a quick look at AGMA 917-B97 table 1 which lists "C" as operating center distance (inches).

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