Best method to align back plate to chuck

Knguyen · Jan 5, 2008

Hi gentlemen,
I am trying to figure out what would be the most reliable method to mount a back plate ( D1-3)to a chuck. Any advice would be greatly appreciated.
Khanh

David Carlisi · Jan 5, 2008

Best thing to do would be to make an arbor. Can you provide more details?

Knguyen · Jan 5, 2008

It's a 5" 6 jaw adjust true chuck. The back plate is D1-3 and has 3 holes evenly spaced at the periphery. I am thinking of mounting the back plate on the lathe's spindle . The chuck is allowed to clamp a test bar on the tailstock. Assuming the tailstock is well aligned, the 2 components are brought together and held in place with C clamps. The assembly is taken to a table where a transfer punch is used to mark the location for the screws. Since I have never tried this, I am not sure if it would work or could be a set up for errors.

Jon Bohlander · Jan 5, 2008

There should be a counter bored area on the back of the chuck. The backplate is mounted on the spindle and turned to match this counter bore. This is what provides alignment. The bolts are just to hold it together. There are two schools of thought on the fit of the diameter of the backplate step to the chuck counter bore. One is make it a close fit so it can't move. The other is leave some clearance so the bolts can be loosened and the chuck tapped around to run true. Sort of a po' boy adjust-true. Personally my feeling is anything that is easily adjusted just as easily becomes mis-adjusted.

Troup · Jan 5, 2008

Jon
Given that the chuck in question is stated to be adjust true, as it comes out of the box
<G>
(Yeah I know I cheated, I don't usually read posts)
I think your method 1 sounds like the way to go

Knguyen · Jan 5, 2008

Thanks John,
It always helps with someone with experience. I love this forum.

eKretz · Jan 5, 2008

If it's an adjust-tru chuck why would you remove the ability to adjust it? Bad idea. As the scroll wears, you WILL need to adjust it when chucking different diameters of stock. Just ask anybody with a 3-jaw non adjust-tru chuck that has a bit of scroll wear. If you leave the face bolts snug, but not supertight (Just loose enough that you can still move the chuck with the adjust-tru setscrews) it will stay put when you adjust it, yet still not be a pain in the tuckus to adjust. I routinely cut the counterbores on our set-tru chucks bigger when we get them new to allow a little more adjustment than factory.

aboard_epsilon · Jan 5, 2008

Jon Bohlander said:
There should be a counter bored area on the back of the chuck. The backplate is mounted on the spindle and turned to match this counter bore. This is what provides alignment. The bolts are just to hold it together. There are two schools of thought on the fit of the diameter of the backplate step to the chuck counter bore. One is make it a close fit so it can't move. The other is leave some clearance so the bolts can be loosened and the chuck tapped around to run true. Sort of a po' boy adjust-true. Personally my feeling is anything that is easily adjusted just as easily becomes mis-adjusted.

another is to slope the sides of the counter bore ....so that it just pulls into centre at the bottom of the slope.

all the best.markj

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Best method to align back plate to chuck

Knguyen

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David Carlisi

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Knguyen

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Jon Bohlander

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Troup

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Knguyen

Cast Iron

eKretz

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aboard_epsilon

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