Just for fun
Brass Thumbscrew

© Frank Ford 2004; Photos by FF

I'm currently finishing up a project - the Tinker Tool and Cutter Grinding Jig, using Guy Lautard's castings and plans. It has been a good learning experience for me, both fun and challenging. If you're in the mood for a good machining project, I reccomend contacting Guy (http://lautard.com). So far, my only regret is that I didn't take photos as I went along.

I'd finished enough of the parts to start assembling the tool, which has a little sliding safety stop that's secured by a thumbscrew. It seemed like a time to celebrate a little, so I decided to make a fancy little item for this use. Here's what I did:

I found a small piece of 3/4" brass and peeled down to the major diameter for 10-24 threads:


And, I threaded the end:

Making this little screw was to be strictly fun, and, except for the threads, no dimension was critical at all. I figured threading would be just about the only operation that would require starting over if I boogered it, so I did that part first. And, I designed (mentally) the thumbscrew so I 'd have minimum difficulty in holding it with collets.

I turned back a bit of the diameter to make the thumbscrew a bit smaller:

Without actually measuring it, I simply gripped it with my hand to get a feeling for its size.


I have a set of fine straight cutting rolls for my knurling tool, and I set the lathe at its slowest (95rpm) speed and, using a flood of spray lube, I managed to get a nice knurl on the brass rod:


Just using the carriage and cross feed screws simultaneously, I roughed some material from about the center of the knurled area toward the threaded end, trying to simulate a curved cut:

I also turned down the diameter of the brass leaving a ridge of exposed knurling about 3/16" wide.


Taking the tool post off and replacing it with my lathe tool rest , I used a small chisel with a sharp point to turn some decorative elements:

By holding the tool down at the very edge of the support with my left thumb, and swinging the handle around with my right hand, I was able to make some very nice inside curves. I worked at about 1500 RPM to form the shape and cranked the lathe up to about 3 grand to do my finishing, finally using a bit of 600 grit silicon carbide paper to smooth the curved surfaces.

Once I felt I had the shape and finish I wanted, I parted off my thumbscrew:

Yeah, the tool is sticking WAY out, but this is free-cutting brass, so parting went smooth as glass.


Because I do a lot of repair work, I bought a full set of moderate quality collets, and here's why:

All I have to do is stick my part into collets until I get a good fit. There's just enough of the smooth diameter next to the knurl to allow me to grip it securely in a collet.


Back with the tool rest, I used a flat chisel to form a dome shape on the end of the thumbscrew.

And, here it is, in place on my Tinker:



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