how thin is too thin?

[eugenebrooks]

Originally Posted by sanddrag

I'm designing a gear to go on the Chiaphua shaft. Specifically, it is a 17 tooth 32 pitch with a length through bore of maybe .75" or so. It will have a standard 2mm keyway in it.

This size of gear, with the .315" bore to go on the Chia and then the 2mm keyway leaves only about .028" between the top of the keyway and the bottom of the "valley" between teeth. Is this too thin?

Compare the shear strength of the key with the tensile stength
of the cross section of the gear that you are concerned about the
thickness of, assuming generic material strength values for carbon steel.

As your second cut, you can make a setup to perform a strength
test, using a shaft that you make so you don't waste a CIM motor.
If the gear tooth breaks first, you are done.

Finally, with all the concern about set screws coming loose and all
the safety measures suggested as a backup, and the fact that we
lost our short set screws, etc..., we TIG welded our spur gears on
the end of the motor shafts this past season. Cut the shaft so it
is flush with the end of the gear, wrap the gap between the gear and
the motor with a well soaked rag, and turn your welder loose on
the problem. The welder needs to be both good and quick at getting
the job done, and needs to be equally quick with another wet rag to
cool off the metal before much heat travels into the shaft.
The keyway could be optional...