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Adapting antique sewing machine handwheel/flywheel for Watchmakers lathe

I'm developing a knurling tool for the watchmakers lathe that exerts equal pressure from the sides, on center to the work to be knurled. Because a watchmakers lathe is intended for precise and delicate work, the motor and pulley system will not drive the work around while the pressure is being exerted to make the knurl cuts.
I was going to make a custom larger crank handle with a collet-type grip on the rear of the spindle just behind where the draw bar slides in. As I was designing this it dawned on me that antique sewing machines had some beautiful hand wheels that I could adapt for this purpose.
hand wheel adapted for the watchmakers lathe

I machined off the protruding collar on the inside of the cast iron hand wheel as well as reduced some weight by removing material off the back. This also served to shape a broad flat to mate the adapter to.
Removing collar from hand wheel

I set about making the brass and steel adapter to grip the spindle.
Machining brass adaptor collar for hand wheel
Drilling collet retaining screw holes for brass hand wheel adaptor
Milling hand wheel cap screw recesses for brass adaptor
I then needed to fabricate the internal finger/collet out of steel. It's very low profile and short so I needed to do this with care. You can see some nicks in a few of the photos as I had a near catastrophe on a final deburring pass when the bit caught. I used the slitting saw and the heavy duty cross slide with the vertical table to make a series of radial relief cuts followed by longitudinal cuts to form the fingers. I soon had the adaptor completed.
machining the pressure collet
Setting up the cross slide and machining head to drill exact holes
Close up machining holes
Here you can see all the parts being installed. You slip on the adaptor, tighten the collet set screws and then slide the hand wheel on and fasten it with the 3 screws in the back. Because of the dished out overhang of the hand wheel, there wasn't good access to permanently mount the adaptor to the hand wheel and simple access the set screw fully assembled, hence the two steps. Only takes an additional minute and really holds like iron with no damage to the antique spindle shaft.
Installing hand wheel adaptor collar

tightening hand wheel adaptor collar set screws

All parts for adapted hand wheel
The hand wheel attaches to the adapter via three 8-32 cap head screws.
hand wheel mounted to lathe spindle with brass adaptor
The draw bar still fits quite nicely and does it's job.
Hand wheel showing flange of inner compression steel collet

Hand wheel with draw bar in place

I mounted the hand wheel to test how well it gripped and just for grins, I ran the lathe. It spun true and vibration free!
Fully functioning hand wheel/flywheel mounted on watchmakers lathe

What I didn't expect was the very useful flywheel effect that keeping the hand wheel mounted for other operations would have. It dramatically increased the depth of cut I was able to take without slowing the lathe and additionally, reduced chatter and vibration on a number of other milling operations since mounting the hand wheel. It's also extremely pleasant to hold and use for all kinds of positioning tasks and the spokes give great leverage.

As an update to this post, here's a video using the hand wheel for doing manual tapping of a part held in the 3 jaw chuck. The operation was almost effortless and the control and sensitivity is very high.


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