Friday, September 20, 2013

Bill Marvel’s Toolpost Mount for Dial Indicator


“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.”

Bill Marvel

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