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Lathe Gear Train

thestelster

thestelster

Ultra Member
Premium Member
Well, I decided to replace the bearings of my lathes gear train, and clean up all the damaged teeth.

The original bearings were shot. They were 6303zz shielded, but replaced them with sealed to keep all the crap out.

The gear teeth were all chewed up for some reason. That's the way it came when I got the lathe 30 years ago. Maybe they were all bouncing around in a bin at one time?

So I turned an arbour on the lathe, attached a gear and removed a couple thou', just enough to get rid of all the burs and dings. Then used a 1/4" diameter round stone to dress the corners of each tooth...manually!

Reassembled, adjusted tooth backlash, drizzled gear oil on the gears, and all good. Quite a bit quieter too.
 

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Quick question on the arbor.... does it hold the gear blank simply by squeeze fit? or is it tapered/keyed etc? I haven't cut any gears yet but I keep wondering what keeps the blank from 'moving' under the force of the cutter.
 
kevin.decelles said:
Quick question on the arbor.... does it hold the gear blank simply by squeeze fit? or is it tapered/keyed etc? I haven't cut any gears yet but I keep wondering what keeps the blank from 'moving' under the force of the cutter.
Click to expand...
I chucked a piece of 2" HR steel, and turned a section down to a very close tight slip fit for the gear bore. It's only held in by a 1/4"-20 bolt and that thick washer and against the shoulder of the arbour. Because I was only removing a couple thou' from the OD, there was very little torque. Even if it slipped a little, it wouldn't have mattered. Also, these gears didn't have a key slot since they where holding bearings.

If I was to do some heavier turning, I would have used a larger bolt. (Think how your bench grinder grips the wheels.)
 
kevin.decelles said:
Quick question on the arbor.... does it hold the gear blank simply by squeeze fit? or is it tapered/keyed etc? I haven't cut any gears yet but I keep wondering what keeps the blank from 'moving' under the force of the cutter.
Click to expand...

Underneath your question, I sense a deeper one indirectly related to what Stel did. Ignore me if I'm off base.

Generally speaking, gear tooth cutting is done with the cutter moving in a plane that is 90 degrees to the plane of the gear body. No cutting force is trying to rotate the gear. All forces are trying the bend the plane of the gear or push toward the gears axis. So accidental gear rotation is unlikely. The biggest concern is chatter/vibration induced rotation.

This aside, Stel points out quite correctly, that it doesn't take much bolt tightening torque to translate into extremely high clamping force. I'd be more worried about the arbour turning in the chuck than the gear turning on the arbour.

Again, ignore me if that's not what you are wondering about Kevin.
 
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