Thread: Thumbscrews for Spofford braces

Or you could just buy them.
1/4" 20T - 1/2" (12.7mm) Wide Thumbscrew - each | Workshop Hardware & Fittings - Carbatec
A quick search brought up a few options.

I've got a couple missing as well, haven't attempted to make a replacement. I think they're about 7/16" 14tpi.
Cheers,
Geoff.

I've made plenty of those types of thumbscrews, but in wood! I turned a ball on the end of a shaft of the desired diameter, threaded the shaft, then cut away a disc on each side of the ball, and shaped the finger grooves with rasp & sandpaper: G4.jpg

If you're lucky, you might find the right bit, but most of the thumbscrews you see now are tiddlers like the ones NC found. I reckon it would be fairly easy to make something pretty convincing in brass. I wouldn't do it the way I do wooden ones as it'd be rather wasteful. I'd start by threading a bit of 7/16 (or whatever the actual size of your thumbscrew is), into a bit of brass bar of a suitable thickness, then hacksaw & file it to shape. Loctite the threaded part in when you're finished & cut the shaft to length....

Cheers,

I've not previously taken much notice of the thread characteristics of the thumbscrews of Spofford braces, so to now say I'm a bit confused is an understatement. I've got a few ranging from early Fray & Pigg to Stanley Rule & Level Co and there seems to be a variance across them all, some 7/16" 12tpi, others 13/32" 12 & 14 tpi. There doesn't seem to be any relationship between the sweep of the brace and thumbscrew size.
The first photo shows a chuck simply using a screw. This is 3/8" 16tpi, I can only assume that the original thumbscrew has been pinched for use in another brace and the screw substituted.
That photo also shows two profiles of thumbscrew used and a home made thumbscrew, this home made jobbie looks pretty old.
The second photo is the chuck with a nut welded on to accommodate a bolt. Also pretty old repair, the thread in the brace has been stripped and the nut welded on to fix the problem. Incidentally this is the first Spofford I ever saw, found on a station scrap heap (resources depot) in the Pilbara probably 30+ years ago.
Cheers,
Geoff.