Notes on making a lathe mandrel handle

This is one of those extras that you don't know how you got by without. It finds uses in threading (using tailstock-mounted dies and taps), winding up springs, and for turning very large diameter objects or where chatter is a problem (such as using form tools or cutting large diameter worm shafts). I didn't have any specific design in mind when I made it, but just knocked something together from what was at hand. Luckily, I had two milling vices both using the same type of handle, both having a square hole broached in the end of the same size. I decided to adapt one of these for use as a lathe mandrel handle.

The handle has a 6" throw which is a bit on the large side for fast turning, but offers great leverage for other work. It's not much use for tapping smaller than 2 b.a. for lack of 'feel', and there would be a risk of snapping the tap. For more general use perhaps a throw of about 4" would be adequate.

The part of the handle which fits into the mandrel is made to expand in place using the round knob you can see in the photo. Turning this knob causes a cone (10 deg inc) to be drawn into the split end of the hollow shaft and this is sufficient to firmly lock the handle in place. The cone is prevented from turning by a small stub inserted into the side of the cone and running in one of the machined slots in the shaft. Additionally, the screwed rod driving the cone, and which runs in the hollow split shaft, has a grub screw located in a groove preventing the rod moving up or down in the hollow shaft. Unscrewing the knob therefore positively forces the cone out thus freeing the handle. If it were not for this feature the handle would remain jammed in place requiring a thump with a hammer to loosen it.

The end of the hollow shaft was made square to fit the existing hole in the vice handle, which can of course be removed if ever it was needed again for another job - it was not modified in any way. The drawings (when I get round to scanning a decent copy) are self explanatory but the dimensions were made off-the-cuff, as it were, so I expect you to modify them as required.

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