Need Help!- Need help with cutting gear teeth in shaft

[CJdave]

I have a job here in the shop that needs gear teeth cut in a round bar to mesh with a gear rack on a door. The shaft will have 3 sets of teeth cut in it to mesh with 3 racks on a sliding door. Shaft is 304 ss, gear rack is plastic. We are working with 14.5 pa 10 pitch gear rack here. Shaft is 1.3" od. that should give me 11 teeth on the shaft. Cutting on Millport bed mill with centroid control full 4 axis capability. Shaft will be held in the 4th axis. I am comfortable with writing the program and work holding. What I don't know is what I need for a cutter? And some feeds and speeds, doc for running in 304 ss.
I have enough knowlage of gears to be dangerous, but not enough to be comfortable.
I looked at MSC for a cutter but the only thing that is close seems to be a #6 cutter and that is only good for 17-20 teeth?

Please someone school me on cutting this gear!

Thanks Dave

[RICHARD ZASTROW]

A 10 dp pinion with 11 teeth will have excessive undercut. Not a good idea but can be done. Problem is it requires a generating cutter like a hob or shaper.

The form milling cutter will not produce the needed undercut.

This is often solved by using long and short addendum gear teeth.

I know this may be foreign to you but there is probably good info on the subject in Machinery's Handbook or a desk quick reference "Gear Design Simplified"
ISBN 0-8311-1159-3 I bought mine for $34 years ago, still available. Well worth the money.

Dick Z

[CJdave]

Yea I kinda figured that the gear would be not ideal. The tolerance on this rack/pinion set is very loose, it is a hand operated door opener/closer. I am duplicating the original design because they need 3 new units. I need to find a way to machine this in house. Could I achieve the undercut by making 2 cuts in the same tooth with the cutter and rotating the shaft to give the under cut? Gear cutting is new territory for me. I do have the machinery's guide and did some research obviously the small dia of the gear shaft with a 10 pitch is most of the problem. but it was done on the original design so I know we can duplicate it.

Thanks

[keebler303]

If you have a cutter that matches the form of the rack, you should be able to take multiple cuts to give you the undercut you need. You would need to rotate the shaft and move the cutter to mimic how they would move when they were meshing. Basically using multiple passes of the cutter to simulate what a hob does, if that makes any sense.

Matt

[CJdave]

Ok, that is what I was thinking. So not having used a gear cutter before, what should I know about feeds and speeds? DOC? Can i get away with HSS in 304 ss? I am probably not going to use this cutter ever again or if I do it would be a freak thing...

thanks

[RICHARD ZASTROW]

Those form cutters are usually HSS. Feeds/Speeds same as if you were milling a slot in in any other 304 SS. The cutter mfg. should be able to tell you, particularly if it's coated.

Dick Z