4jaw centering tip

[mklotz]

In my little treatise on centering work in the 4jaw chuck...

http://www.homemadetools.net/forum/c...aw-chuck-27241

I advocate mounting a dial indicator to a permanent easy-to-set-up arrangement. A typical arrangement would be to fabricate an aluminum piece to mount on the QCTP and bolt the DI to that. Then, when centering, the DI can be slapped onto the QCTP, automatically aligned with the spindle axis, and you're ready to start moving chuck jaws.

The referenced procedure has you touch the DI to the work, adjust to roughly mid scale, and align the DI pointer with zero on the scale.

Now, here's where the hint comes in. Adjust the DI scale so zero is at your 3 o'clock position. Following the instructions, the DI needle will point to this 3 o'clock position.

Turn the chuck 180 degrees. Because the work is not centered the DI needle will no longer point to zero. But now, ITS POSITION WILL GIVE YOU A VISUAL INDICATION OF WHICH WAY TO MOVE THE WORK. If the needle is at the 1 o'clock position, it needs to be moved toward you and, so, the work needs to be moved toward you; loosen the front chuck jaw and tighten the back one. If the needle is at the 5 o'clock position, it needs to be moved away from you and so must the work; loosen the back jaw and tighten the front one.

Using this hint is not essential to the procedure but it does make the movements involved a bit more intuitive.