Inspired by John Mills, I decided it was time I made a locking lever for the quick-change toolpost on my Colchester Student 1800 lathe. Nut is made from 40mm EN8 steel, tapped 16mm for the toolpost. Shaft is 16mm EN8 with two flats 16mm wide milled across it for a 12mm spanner.
I had a 16mm tap for the post thread, but could only find a half-inch UNC (13tpi) tap for the handle socket. No sign of a die or die-nut that size, not even a 12mm die, so I used a single-point carbide turning tool to machine a half inch UNC thread on one end of the handle. Lucky that the 1800 does metric and imperial without gearwheel changes.
Other end of the handle is threaded 10mm with a die-nut I found in my dad’s old toolbox. Just my luck though, no sign of a 10mm tap anywhere, so I ground a taper and some flutes into an old high-tensile 10mm bolt. I made the knob from a bit of 6082 ally bar and used the bodged tap to thread it. Worked pretty well, although I drilled it to 9mm and I guess it rolled the thread more than cut it.
The threads are good and snug, and I had to use the flats on the shaft to get the ends on. No Loctite needed!
That rolled thread in the ally doesn’t look too horrible
Had to use a lot of torque to get the thing assembed
Finished item in place on the toolpost. For scale, that is a 10 inch chuck in the background