Rear chuck, is the shaft really aligned???

[kiinstructor]

When I put a shaft in my lathe through the headstock and indicate it in the front, can the shaft be offset through the headstock even if the reach chuck indicator is zero? What I mean is can the shaft be crooked between the front and back chuck thus causing a slight bow and the incators be on?? A friend of mine who is a machinist told me the as long as the part of the shaft that is in the front jaws says 0 then the hole you drilling will the tru with the shaft. I dont think that is true if the shaft is off in the back. I think you must have the front and back chucks dead aligned to make a true running shaft. IF that is true, how do you align the back chuck with the front????

Thanks
Mark

 

[rhncue]

When I put a shaft in my lathe through the headstock and indicate it in the front, can the shaft be offset through the headstock even if the reach chuck indicator is zero? What I mean is can the shaft be crooked between the front and back chuck thus causing a slight bow and the incators be on?? A friend of mine who is a machinist told me the as long as the part of the shaft that is in the front jaws says 0 then the hole you drilling will the tru with the shaft. I dont think that is true if the shaft is off in the back. I think you must have the front and back chucks dead aligned to make a true running shaft. IF that is true, how do you align the back chuck with the front????

Thanks
Mark

If both chucks are running true on ends of the same spindle, rod, piece of pipe or tree limb and it is straight then they will be concentric with each other. Now if you drill or bole a hole in the front of the shaft it will be in perfect alignment with those two points on the shaft. If the shaft bends in the middle or past the rear chuck then this hole, of coarse, will not be aligned with those areas. The shaft needs to be checked for straightness between centers before putting in the lathe for further work. The old adage garbage in garbage out would be very appropriate in this instance.

Dick

 

[conetip]

The chucks need to have zero swash to each other.Other wise the work piece inbetween can be bent slightly.
Having a fairly short jaw length will reduce this effect or using a bushing or collar.

 

[scdiveteam]

Hi,

If you are running less than .001 run out on your chuck and the back chuck is off a couple of thou 29 inches away at the back chuck, I don't think that should have that big of an overall adverse effect.

If your back chuck is running out a little, you can always use paper to shim the shaft or butt if you are having some kind of problem and wish to eliminate the back chuck as the culprit.

My back chuck is off a little from time to time and I have to recenter the collar and re-tension the set screws. I have noticed that when it was off and my center hole was wobbling a little, it did not impact the roll of the cue when assembled. It is still a good idea to have it as close as possible.

Rick G