Fitting a new backup plate to three jaw chuck

[TUE]

any one have hints to get backup plate under five thou at six inches measured on shaft eight in. in front of chuck? I will use it on universal indexer.

 

[joeby]

TUE,

Normally, a backplate is machined backside first, then mounted directly on the lathe spindle to face the chuck mounting surface; but in this case it sounds as if you are making it for a milling attachment that doesn't have the same thread or register, is this correct?

If you need to make it to fit something with a different size spindle than your lathe, I would turn and thread a stub to match the spindle it needs to fit and, without removing the stub from the lathe, thread the backing plate on this stub and face it off. If you still have runout problems after doing this, I would check the spindle on your indexer for runout or damage.

Kevin

 

[TUE]

Ok- the backup measures less than a 5 tenths on the indexer and the chuck does too when chucked  in the lathe chuck. I purchased a new indicator yesterday and am hoping for warmer weather tommorow to recheck things but I am wondering about the chuck jaws.

I need to add a correction: the chuck is small enough I chucked it in my lathe chuck and it also reads just half a thousand off on back/ mounting side.

 

[TUE]

Thanks Kevin: I made a stub and redid the mount side and it came out less than a thousand at six in from the chuck on a shaft chucked in the indexer chuck, so i am very happy!

 

[joeby]

TUE,

That sounds better!

I'm glad that fixed the problem for you. 8)

Kevin