Set-true question

[bcall2043]

I have seen ads for “set-true” chucks and a search turned up enough comments in the threads so that I believe that somehow you can adjust the individual chuck jaws to compensate for error in the scroll but don’t understand how this is done. My question is how is the adjustment made and is this something that can be retrofitted to an existing 3-jaw chuck?

Thanks for any information.

Benny
In middle Tennessee, USA

 

[Bobby Bailey]

Benny, It's not normally the individual jaws that are adjusted but, the body of the chuck to bring all the jaws into alignment. The body of the chuck has 4 screws that work against a boss on the chucks backplate like a 4 jaw and used to center the chuck/chuck jaws. Hopefully some of the other guys will come on that are more adept at describing things.

 

[bcall2043]

Bobby,

Thanks for the reply. Your explanation makes sense and it seems that it would not be an easy modification to make to an existing chuck. What you describe would require that the chuck be counter bored and a back plate that fit into the chuck body. Just adding adjustment screws into the chuck could be difficult. I put a file on a chuck once and if I remember correctly it was somewhat hard.

Thanks, Benny
In middle Tennessee, USA

 

[goldenchips2]

OR...
You could make the backplate so that the chuck would fit INSIDE it,
Easier than making the backplate fir INTO the back of the chuck...
There was a write up on a set tru 5C chuck in Home Shop Machinist, or Projects in Metal somewhere in the last year...
I made one for my lathe, I love it...

 

[bcall2043]

OR...
You could make the backplate so that the chuck would fit INSIDE it,
Easier than making the backplate fir INTO the back of the chuck...
There was a write up on a set tru 5C chuck in Home Shop Machinist, or Projects in Metal somewhere in the last year...
I made one for my lathe, I love it...

goldenchips2,

Thanks for your tip about the HSM chuck article. I was near a book store today and checked to see if they might have a old copy left. They did not have a copy of the issue you mentioned but the new Jan/Feb 2012 copy had part 2 of the earlier "Chucks and Chucking" article by Randolph Bulgin and on page 65 was a good explanation of the "Set-Tru" with the screws in the chuck body with photos.

How it works is now clear. I will put your method with chuck into backplate and the screws in the backplate on my "round-to-it list".

Thanks, Benny
In middle Tennessee, USA