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Internal involute spline help


Feb 10, 2011
Boise ID
Could use some help with modeling up an Internal involute spline. everything I am doing does not seem right. Whatever I come up with does not look like the print given.
No model will be provided.
I am using the Mastercam Gear.dll, or anything I can find on the interwebs. FreeCAD has a feature that gives an ok spline, and a Solidworks formula also gave something but when comparing to the print something is still off.

Probably can't tell from the picture, but Mastercam is adding a curve to the end of the splines. The print looks straight. But table 1 says involute.

It looks like it should be a standard S.A.E spline. It confuses me when it says pressure angle, and the dimensions are off from S.A.E (adding for fitment?).
Is there a better way to go about this? Did I set up the software wrong? (so many questions).

Tried a few other variations where I truncate what Mastercam gives me
If the addendum is made straight, this one looked very close to the print.

Thanks for the time.
When they say SAE spline, it is most likely a J500 spec spline.
That is a straight wall serration. Not involute. That spec started right after WW2 and was officially recalled for new designs in 2000. But is still being used by many.

The recommended replacement is ANSI B 92.1. That is a involute with the curved walls.
That is when you get pressure angles and tooth width or space width called out.

There is a solidworks add-in called Geartrax that can model accurate spline and gears of many different standards. The Gear generator option in Esprit is also good for this.

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I basically have two involute splines to model up and this is a rare thing for us to do. Normally we would have a solid model.
Thinking they didn't want to figure it out. left it up to us.
Hate to spending money on software that will not get used again.
Any options out there?
I hear freeCAD can, but not understanding how to give me the right form.
free cad.PNG
I think I got it.
Will have to modify the major diameter and the root diameter, after freeCAD gives me some lines. I believe it will work.
Well crud.
FreeCAD says it is using ISO 4156
Only one print, of the 5 in this series says, ANSI B92.1 1996. The other 4 don't say anything.
I might have to redraw some splines.