Monday, March 15, 2021

One of the Big Problems of Machining is How to Hold the Workpiece

 If you are cutting on a cylinder face, you hold it in a three jaw chunk.  In this case, I want to cut a bunch of cuts on the outer edge of a disc made of Delrin, to make the knob easier to control.  (The knurling attachment for the Sherline is limited on diameter.)  To make the cuts consistently far apart, I need to mount the disc vertically on a rotating table.  A chuck of any sort will have jaws in the way.  The rotating table uses a 3/4"-16 to 3/8"-16 adapter so that the Sherline chuck can be attached.

The workpiece cannot have a through hole larger than .152".  (That's the shaft diameter onto which it slides.)  I needed a way to hold the workpiece securely while rotating the workpiece.  So I put a .152" hole through a 3/8" hex head bolt, then a 6-32 x 1.5"? screw through the hole.

The hex head bolt screws into the adapter hole:

I will put the workpiece on the screw, tighten the wingnut (and probably a lockwasher) and voila!  I am only turning the table a few degrees a minute.  I wish that I had a CNC rotating table.  I have not yet heard back from Sherline about the cost of doimng that upgrade, but I can do two knobs manually.

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