View Full Version : Replacement gear 'rings'

The Fixer
03-06-2009, 12:17 PM
Hi all, I am restoring a Hercus 9" lathe which has some broken gear teeth on several gears. I would like to cut some replacement gears and some "ring gears" to press onto original gears (like the backgear which has a different size on each end) after turning down to a nominal dia rather than machine the entire part.
First question is, has anyone done this yet? (ringgears)
Secondly how deep do I need to cut the teeth for the various size gears? I have purchased the necessary cutters for correct dp etc.

Spin Doctor
03-06-2009, 04:16 PM
First what DP or Module are the gears. The cutters should say on them what the whole depth is. If they don't then if they are say a 12DP gear then they would be 1/12 x 2.25 or .1875, 10 DP would be .225. 20DP and under things are a little different but not much. Any gear you mount on an arbor is technically a "ring gear". But I think that as long as the ring is 2xs the whole depth of the tooth in wall thickness and has sufficent press (say .005") then you should be alright. One idea would be to have a step inside the bore that hits a shoulder on the old gear. Then when you arre cutting the new teeth have that as the side you are feed against so any pressure from the cut forces the ring against the shoulder. Also drilling and tapping for a coulpe of set screws at the fit diameter of the ring will act as insurance that the ring will not spin in service.

The Fixer
03-06-2009, 06:29 PM
I do see now there is a WD dimension on the cutters, Presumably that's the depth to cut. Seems simple enuf when u read all the info!