Drawing instruments

[Anthony KnightsParticipant @anthonyknights16741]

what thread

[Anthony KnightsParticipant @anthonyknights16741]

I have a number of drawing instruments (compasses etc) that I have aquired over the years and actually used at one time. They range from cheap school sets to more expensive draughtsman type equipment. Over the years some of them have lost various bits which I would like to make replacements for, now I have a lathe. My question is, does any one know what threads were used?

Some of the cheaper ones seem to have threads ranging from M1.4 to M3 but my thread gauges don't seem to fit some of the others. I suppose they could be BA, because that's the only set of gauges I don't have. Any information will be appreciated.

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[Howard LewisParticipant @howardlewis46836]

Could be anything, depending upon the manufacturer; BA, Metric or even tiny Imperial..

Have you a set of Thread Gauges, so that you can check the form and pitch of the various threads, presumably all male?

1.4 mm is given as the clearance size for 12 BA,

Tubal Cain's Model Engineers Reference Book quotes 12 BA top diameter as 1.3 mm ( 0.0511 ), and 81.9 tpi and 11 BA as 0.059" (1.5 mm ) top diameter, and 90.7 tpi.

You look to have a lot of measuring and checking ahead of you before cutting metal!

Howard

[Michael GilliganParticipant @michaelgilligan61133]

Thury is probably a good candidate: **LINK**

https://en.wikipedia.org/wiki/Thury_thread

MichaelG.

[Author]

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