broken clamps

[naughtyboy]

been sorting out my late uncles shed and found loads of broken c-clamps.
they look like cheap ones and they are broken on castings, threads are square.
are they acme threads? if so how do i found out what sizes they are?
would like to re-use threaded sections on some clamps im looking at making for a jig i need.
plus im i dont like seeing anything wasted.
cheers

 

[shenion]

If they have squareish-looking threads, they'd be ACME. ACME does have a 29-degree angle between the inside faces.

If they are old, it could have square threads.

You could cut the head of the clamp off and weld it on as a nut elsewhere.

 

[naughtyboy]

broken area looks grainy like its cast, whats best way to weld it?
only got mig and arc.

 

[Justme]

Might be better to cut the threaded bit of but leave a flange that can be drilled & bolted into it new position.