Geoff,

The fact that they look like a left and right setting tool makes me think they might be used on something like a fertilizer spreader, or similar, where contra-rotating throwers are involved. Just cannot understand why there is a negative setting.

We had to change the settings on a spreader recently and the instruction book was like a minefield to negotiate – what with prill size, machine height and slope, width of spread for the desired rate, ground speed, etc.

If they are anything to do with mills and lathes I would have no idea, but at least this is giving the thread a ‘bump’.

..holders for (maybe the circular-type) thread form tool?

.

The threaded hole, plus two ‘dowel holes’ suggests to me that these might be for attachment to a beam [cf Trammel Heads] … The handed pair, featuring fine adjustment, then makes a caliper.

I would probably look to the picture-framing business, or similar.

MichaelG.

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Edit: ___ So I did look, and found this : https://youtu.be/x1n9tQrQodk

Not the same; but perhaps a family resemblance ?

Edited By Michael Gilligan on 22/05/2020 10:14:05

The gauge is a Douzieme Gauge. Used to measure thickness of curved surfaces, for example watch cases. Increments are in 12ths of an inch. 1/12 x .72 = 0.6"

regards Martin

Now available on well-known auction sites but calibrated in millimeters.

Tim