Instructions

SHERLINE 4-Jaw Chucks
Instructions for Use
Because of the varied uses of the 4-Jaw Chuck it would be impossible to write a comprehensive set of
safety rules to cover every specific use, other than simply suggesting the use of liberal amounts of
"Common Sense". If you're not sure of your set-up, it probably isn't good enough. Get a machinist with
more experience to advise on a safe set-up. Be sure to remove the chuck key before turning the spindle
on. Work Safely!
The screws that move the jaws are 20 threads per inch (T.P.I.). A complete revolution is .050". If you
keep this number in mind when indicating a part in, it can speed up the process.
First, use the lines machined on the face of the chuck to roughly align the part concentric with the
chuck. With an indicator, read the run-out. Move the jaw closest to the high or low point 30% of the
total indicator reading in the proper direction.
NOTE: We recommend the 30% figure because the high point of a part will very seldom line up with a
jaw. Moving a jaw too much can cause "chasing your tail", or simply moving the high point around the
chuck.
EXAMPLE
The indicator shows a .030" run-out. 30% of .030" is approximately .010". If one revolution of the jaw
feed screw is .050", then a little less than a 1/4 turn will be .010". Back the jaw out this amount and
tighten the opposite jaw. DoNOT tighten the jaws beyond "snug" until the part is running within .005"
T.I.R. (Total Indicated Reading). Repeat this process until the part runs within your specifications.
Once the part is running within .002" T.I.R. it can usually be "brought in" by a final tightening of the
jaws. It should also be noted that the chuck jaws are ground with a slight angle to allow the jaws to
apply equal pressure to the tip and base when properly tightened. This angle amounts to less than .001"
on the jaw surface.