arbor

[Don1954]

Hi im trying to get the arbor and pivot straight, how straight does it have to be? when i put the gear and shalft in the lathe there is a slight wobble. and the gear itself has a wobble i have been messing with it got the gear wobble almost out and the same with the shalft and pivot.

[Bob Tascione]

Hi Don,
Needs to be pretty true. The amount of accuracy required will depend on the type of movement though. Most American production movements are fairly forgiving and may run fine with a little run out whereas a finer, more precise movement might jam from even the slightest run out. Is it possible that wobble is being caused by the chucking in your lathe? If you have a couple of cup centers and can run the arbor/wheel between centers in your lathe you'll know for sure. You can also rotate the arbor while supported between a couple of vee blocks or just a couple of pieces of metal or wood with a V cut into them or you can put the arbor back in the movement and tighten the plates down then spin the wheel to see if you detect any run out. Straightening can be an endless process if your chuck or collet isn't able to grab and hold the arbor perfectly and using these or a similar methods will help you determine if the problem is between your lathe/arbor clamping and also help you see exactly where the bend is on the arbor or if it's a distorted or badly fitted wheel or just a bent pivot.

Bob