What is This Doodad?

Looks like a clamp-on glass circle cutter assembly....

It looks like something that may have been used by someone manually spooling a large spool of thread, cord etc?

The counterweight would be to offset the weight of the spool and the thread would be fed through an eyelet from a bulk source?

wag as usual.

getting close! the version in question uses the counterweight to produce a cross winding pattern?

Naw, it looks more like a dentist's tool.

Bingo. On the counterweight I found Baker Newark, N.J. pat no 14229807 simple and eflicient device more particularly adapted to casting dental iilillay fillings and other articles of irregular s ape.

You guys are good.

The round stud at the bottom right corner of image: Is this threaded to receive a screw? The length and diameter of the stud might be also be clues.

The size of the so-called counter balance indicates whatever is being swung around is of similar mass or more - can you tell us how heavy the piece is?

damn..

and this is not the same

? Looks like a coil winder

Mounts on table.

I believe the official name would be do-hicky.

That's pretty much how my Dad would explain it to me!!!

Shown right way up

Grans knitting and crochet memory's winding bobbins - also along similar lines the hand turned mincer - great fun as a kid. Would be child enslavement these days.

Perfect, and GA!

And what about reply #2?

As well as #5 and the OP response in #7 identifying the item?

This makes a lot more sense than a bobbin winder. For a string/cord winder, the string would go slack during half the cycle. For casting the larger counterweight would be needed to balance the rotating part. At least one part seems to be missing--the forked part to hold the casting apparatus.

I never in a million years would have guessed that use.

So, now we have a new challenge: no one needs it to make dental stuff anymore.

What could it be used for?

Winding thread perhaps?

Jewelry is often cast by doing a lost wax casting process. They use a spring loaded centrifugal device, so this could also be used for making jewelry.