There was some talk of adjustable backplates a while back.
Here's an update.
I just completed an adjustable backplate for the 5" 3-jaw chuck sold
by J&L Industrial. I posted a few pictures in the PHOTOS section in
a folder called Adjustable Backplate. It was a fun project and I'm
real happy with the results.
The test sheet that came with the chuck showed TIR of .002". I
verified this figure on my lathe too.
With the adjustable backplate, I am able to easily reduce runout to
well under .0005". (The needle on my dial test indicator was very
stable. I posted a movie file of this in the FILE section, but it's
a large file, so don't try downloading unless you have a broadband
connection.)
I used 12L14 steel for the backplate. Great stuff to machine!
I made the spindle recesses in the backplate only about .008"
oversize. I figured this would give me enough adjustment play to
compensate for the chuck runout of .002". I used four 10-32 brass-
tipped set screws for the adjustment capability. One of them is
shown in one of the pictures.
Here's a url to go to the photo folder
Here's a url for the video showing the runout
B Flint
