Internal splines

[Piggiron]

What methods/tools are available for cutting internal splines inside a smaller diameter bores, say less than 3/4" ?

[TerryWerm]

They are typically cut with a broach that is made specifically for the desired spline.

[Uncle Buck]

Given the small dimension I think that may be about the best, and only option. We're the hole size larger I would say that would be a perfect shaper job, but I can't imagine that given the small size.

[Adasha_Machining]

Sure, could be a shaper job, or even any machine with a carriage or quill.
I've done internal splines several times on the shaper. I have made two different diameter tool heads. One larger diameter shaft with a square hole at the end for a 3/4" hss square shank tool. One smaller with a brazed on tool.
In this caller case you likely need to grind the profile in the tool itself.
I would grind the appropriate cutter from a piece of HSS stock. It would take a boat load of grinding and if you break the tip off, you gotta start over. But could be done.

[OldCarGuy]

If it's a through bore. The best way to machine an internal spline would be Wire EDM. I came close twenty years ago to purchase one for  my home shop. Needless to say I begged off.. Next choice with be machining a graphite electrode that's easily accomplished on a surface grinder using an indexing head.. Then setting it up in my EDM Machine and burn the spline,, reverse of the electrode...  This is 1.000" diameter

Electrode..


EDM Machine


Here's a simple electrode to grind.. But near impossible shape to machine in steel 

[Uglydog]

Vertical slotter.
I've got one on my Cincy Toolmaster and a much smaller on my Van Norman 6.
Someday I'll finish making the cutter holder for the Cincy. Meanwhile the VN6 and a RT work well enough. Although I haven't made an internal spline.... I have made square holes and square slots.

Should be just a matter of grinding the cutter and managing the RT.
I've no doubt that EDM is much faster. But old school still works.

Daryl
MN