You can buy broaches but they are typically very expensive.
If what you want is in the order of 1-1/2" dia, let me know.
I can prolly dig up something for you.

But if you're talking about RC servos, that's another story.

I've done this kind of thing using a keyway approach.

Secured the key to the cylinder part.

Never even occurred to me that if I put in more keys in I
would prolly get less binding!

I think I used a shaper to cut the inside keyway for the cylinder.

But you could do the same thing on a lathe by running the compound
back and forth, left to right.


DOC

Refugee from rec.crafts.metalworking :-)


"Mike Young" wrote in message
m...
"Si Ballenger" wrote in message
...
On Thu, 29 Sep 2005 16:03:16 -0700, "Brad Smallridge"
wrote:

I have a lathe and milling machine and would like to
make my own parts for servo motors horns, wheels,
or take up spools. But how does one go about
machining that serrated interior hole? Is there some
sort of broach I can get for it?

Brad Smallridge
aivision.com

The below group has a lot of metal maching types of questions and
answers.

rec.crafts.metalworking

If one couldn't buy an appropriate broach, one would presumably turn,
mill,
and harden some tool steel and make his own. Depending on the quantity,
HSS
will be just fine for aluminium. An arbor press and a simple jig will take
care of the rest. A machinist's vise can substitute for the press.

It would be far simpler to just buy some anodized arms and modify them. Me
personally, I would probably file a flat on the splines and run a setscrew
up on it. Plenty of room to get fancy elsewhere.