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Full fillet root

thread406-52457

Full fillet root

Full fillet root

(OP)
A gear shop that we work with wants to make all of our gears with a full fillet radius. They are currently flat fillet. They are telling me that full fillet is the industry standard now. All my gear books treat the flat fillet as standard, and suggest using the full fillet when needed for strength. My books are pretty old, so what is the standard now?

Thanks,
John Woodward
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RE: Full fillet root

Full fillet. This holds particularly for plastic gears now. The new AGMA stds for plastic gears are standardized on the ABA-PGT original designs, which were all full fillet. Ask for AGMA 1106-A97.

RE: Full fillet root

JL
The standard full depth full fillet radius
is the new standard which is usually
1.25 time the module or 1.25 divided by the
dp for the dedendums.
For shaped gears the ratio might be 1.335
instead to get a proper sap diameter.
The full fillet seems to strengthen the part
even tho the moment arm becomes longer.

RE: Full fillet root

I think it is your preference as both will work. Go to www.akgears.com. There you will see the latest on how to shape fillets to minimize bending stress.

RE: Full fillet root

You must be careful when designing a full fillet radius.  Some people define  a full fillet radius as a constant radius arc connecting the two involutes.  Others define a full fillet radius as a constant radius tip on the basic rack that generates the tooth form or on the tip of the hob tooth.  An error  in understanding what is meant can lead to significant problems with the resulting gears.

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