“I enjoy reading tips and ideas from a variety of forums and web sites. I have learned there are many, many tricks of the trade and many different ways to do things. David Lemereis' YouTube called “Easy Centering the 4 Jaw Chuck” presents an interesting and simple approach to centering stock in a 4 jaw chuck. It may be common to many but it caught my eye. He uses a toolpost mounted dial indicator and two chuck keys to center a piece of stock, square or round, in the 4 jaw chuck quickly and easily.
I only needed a way to mount my dial indicator in a Taig toolpost. It may be obvious to experienced machinists. For the beginner or tinkerers like me, here's how I did it.
I cut off a 2 1/2” length of 1/2” square 6061 aluminum bar. I faced both ends and milled a slot along one edge 1” long to fit the toolpost slot. Mounting the piece in a toolpost on the cross slide of the lathe, I drilled a 3/8” hole to match the shaft of my dial indicator (Center-drill; drill with a 3/16” bit; drill with a 23/64” bit; and finish with a 3/32” chucking reamer). Drill the clamping screw hole with a No. 20 bit. Tap 10-32.
Find the center of the end of the DI mount. Use a slitting saw to cut a narrow slot into the 3/8” hole you drilled. Open one side of the 10-32 threaded hole with a 3/16” bit. I used a single edge razor blade in the slot to act as a drill stop. A 1/2” length 10-32 socket head bolt finishes the part..
None of the measurements I used are critical. I made it as short as I dared (2 1/2”) to clear the chuck jaws with small pieces. The shaft of my dial indicator is a convenient 3/8” in diameter. Measure yours. You can cut the slot with a razor saw or piercing saw, or even a hacksaw if you like. I have learned that laying out and marking up your measurements with a scriber or even a felt tip pen saves time, makes your work more accurate and saves on raw stock. I only made this one three times. I am getting better.”