Holding gear in lathe chuck

[cobra46]

Just got my new 3-1 lathe mostly set up. In the process of rebuilding I broke the smallest feed screw transmission gears. I bought a new gear knowing I needed to modify it. The modifications include boring it out, removing the hub and broaching a keyway.

I was able to hold it by the hub to bore out the ID but I'm not sure how to hold the teeth to cut off the hub. I have a three jaw and four jaw chuck. The only method I can think of is to machine a split bushing with the ID of the bushing close to the OD of the gear. I'm sure there has to be a better way. How have you guys done this?

The gear is a Mod 1.5 14 Tooth

Thanks

edit - added gear info

 

[benmychree]

The split bushing is the safest way to do it, but the 3 jaw may be good enough for such a minor operation.

 

[Latinrascalrg1]

Could you make a mandral to fit the new ID to cut the hub? I would think you could either turn it off or use a parting tool.

 

[cobra46]

The split bushing is the safest way to do it, but the 3 jaw may be good enough for such a minor operation.

I tried to put it in the three and four jaw and neither seemed too secure.

 

[cobra46]

Could you make a mandral to fit the new ID to cut the hub?

Wouldn't it have to be an ID collet to do that?

 

[Latinrascalrg1]

Not quite sure wht your asking but i was thinking a shaft with a slighty tapered end that would slip fit into the gear to lock it into and tightly against your 3 jaw, i dont see a need for a collet of any sort but then again im not a machinist!
After you cut the hub the 3 jaw should be more then enough to hold the gear securely to cut the key way since it wont be rotating.

 

[cobra46]

HAHA.

I'm not quite sure I understand your tapered shaft/mandrel idea but I'm intrigued.

 

[Latinrascalrg1]

Im no picasso but i think you should get the idea.

 

[cobra46]

Got it figured out. An expanding arbor is what I need to make.

 

[cobra46]