The Home Machinist!

I bought a Grizzly milling machine about 10 years ago and now that I'm retired, I finally have plenty of time to play with it. It's a G3617 horizontal-vertical milling machine, and I've used it almost exclusively in the vertical position all this time. I think I have set it up as a horizontal machine only a couple of times. Overall, it's been a good learning tool.

It came with two arbors for the horizontal set up. The fit to the machine is R8, and the arbor diameters are 1.0" and 1.25" respectively. They seem to be nicely made, ground and polished, and with a set of clamp up bushing for each. Also included in the clamp up bushings is one very finely machined and finished bushing, slightly larger than the rest.

I ordered some involute gear cutters in order to make some gears for a project I'm working on. The gear cutters have key ways machined in them, but the arbors don't have key ways.

What gives? Am I missing something? What is the special bushing for? Don't I need a key way on the arbors to drive the cutters?

thanks

The slightly different bushing is the one that supports the arbor in the overarm support. And yes arbors usually have keyways,but with the light load imposed by the gear cutter I would think if you firmly tighten the arbor nut you should be OK. R-8 with a keyway ,look on eBay for one made for use with a angle head on a BP .

My horizontal mill has arbors and all have full length keyways. Most of the bushings have keyways, too. I can't imagine driving a wheel cutter without a key.
You could use your vertical mill setup to cut a short keyway where you will mount your cutter, to avoid trying to cut one full length. Make absolutely sure it is centered, i.e. points to the arbor axis. Cutting a key slot in a bushing can be problematic, but can be done if you don't mind round topped key slots. If you do it with a round top key slot be sure there straight sides on the slots at least as deep as half the width of the key. This will give you enough key shear strength.
I have no clue why one of the bushings has a larger OD. Mine have all sorts of ODs because some are home made and others not.
Good luck.
--earlgo

John: The overarm support on my Horizontal has a brass bushing adjustable for diameter like a collet. It runs on a polished stud that is smaller than the thread minor diameter that clamps the bushings and cutters tightly.
--earlgo

My pratt & whitney mill arbors have no keyways and the sales materials show them cutting things like gears, so it can be done, but as Earlgo says, you can't take as heavy a cut as one driven by a key.

I would advise against milling a keyway in the arbor on the grounds that if you do, there's a good chance the arbor will warp.

Milling identical keyways on opposite sides might avoid that problem and with a 1-1/4" arbor, it would not weaken it enough to matter.

Steve

SteveM wrote: ↑Mon Apr 27, 2020 10:10 am there's a good chance the arbor will warp.

Might be better to suggest that there's little chance it won't.

H