Common Involute Spline Tooth Counts

[gpommeranz]

Hello All,

I'm working on the design of a shaft with 30° P.A. splines. I have the equations for determining the major and minor diameters, tooth stress, clearances, etc but since this is a wholly from scratch design so my space constraints are somewhat minimized. I know for hydraulic pump shafts, SAE has several standard shaft diameters and spline counts. This is for a non-hydraulic application (mechanical driveline) so my question is whether certain tooth counts are more common than others. For example: if I use a 12 pitch spline, are 12 teeth or 13 teeth, or 14,15,16,17, etc more common? Obviously some of it has to do with shaft size but I haven't been able to find anything else.

Thanks.

 

[tbuelna]

gpommeranz-

If your concern is finding US vendors with existing tooling to produce your splines, don't worry about it. As long as you design your spline teeth to a common standard like ANSI B92.1, you should have no problem finding someone to produce your splines. The only suggestions I would make are to use a fillet root, side fit involute spline with a 30deg PA, and make sure your part blanks have adequate relief (internal and external) to permit the splines to be produced on a shaper. For small batches of parts, shaping is usually the most cost effective method to produce splines.

As an example of cost for prototype quantities, around 6 years ago I had an aerospace gear vendor in southern California put 12dp, 20t, cl. 5 splines on a pair of 4340 alloy steel shaft and hub blanks that I supplied. They shaped the spline teeth on both parts and provided detailed inspection reports for just under $900. The invoice listed a machine set-up charge of $300 for each of the two different splines (internal/external), but there were no tooling charges.

Hope that helps.
Terry