Re: On Topic: Splines

Kirk Gordon <kg1@xxxxxxxxxxxxxxx> wrote in

No, not the CAD kind. I'm talking about splined shafts. Splines
are something I've somehow never learned. That's not normally a
problem, except that I have something with an ID spine in it, and I
need to buy or make a shaft to mount it on.

It's an involute spline, with 8 teeth that look like they're too
apart. Like, the thing should have 12 or 16 teeth, but doesn't. The
major diameter is roughly .782", the minor is about .602, and I don't
have a clue about where to look for the specs, details, or how/where
to buy something that will help me.

Any spline experts in the group, or links that might help?

Here is a quick tutorial on splines -

Since your spline is an involute form it can be rolled or hobbed. The
design of the shaft will also dictate whether or not hobbing can be
used. If they don't allow the radius of the cutter at the end of the
spline it would probably have to be rolled.

All hard to say without seeing the drawing.

Other options include form milling and shaving. Star Cutter and others
sell form milling cutters for involute splines and other tooth forms.

Star Cutter -

Star also makes hobs but probably not in a small enough diameter to be
used in one of your cheezy Citizen Swiss machines. There is a German
company that makes small ones suitable for use in a lathe attachment,
but my memory is failing me at the moment. If you are thinking about
hobbing on one of your Swiss machines, I can get their name on Monday.
But you'll need a hobbing attachment and the control option for
hobbing/polygon cutting.

Schwanog makes shaving tools that you can use in a lathe, but with an 8
pitch you'll likely have to take a lot of passes. But it is a cheap
method for producing precise splines without having to spend a fortune
on tooling, attachments, control options and/or machines.

Schwanog -

I believe Schwanog will also make form milling cutters.

If this is a high volume part, rolling is hard to beat. There are plenty
of shops in Michigan that have spline rolling machines sitting mostly
idle. Not too long ago I had a customer that bought a refurbished spline
roller for not a lot of money. IIRC, they bought it from these guys -

Anyway, I have hobbed splines on a lathe before. If you are interested
in going that route let me know and I can give you some more detail.