Startrite Mercury drill

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... welcome to the wacky world of posting photos on this forum: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=103028&p=1

MichaelG.

Actually "standard" metric pitch ie metric coarse and what you'd get over the counter if you just asked for an M16 nut or bolt is 2mm, the 1.5mm pitch is the usual metric FINE value.

16mm x 1.75mm pitch certainly would be an odd ball, even Tracy tools don't do one that matches that, although they do list taps and dies for 16mm dia. in 0.75, 1, 1.25, 1.5 and 2mm pitches.

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Exactly my thought, Rod ... When I asked:

... Have you inspected the new nuts ?

MichaelG.

Edited By Clive Brown 1 on 21/04/2020 15:12:49

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So my question is still open

One parameter has been checked, and is GO

... but the tpi and thread-form of the nuts remains a mystery.

MichaelG.

NOT according to the chart posted by Gary on the first page🙂. And a lot of the other charts on the web. As I noted earlier it would be unusual, but not unknown, for a company to make ‘specials’ so spares supplies are limited mostly to themselves (usually at a much-inflated cost). I’m now thinking it is more likely some n———-l has supplied metric instead of imperial.

This has provided a not-so-welcome break from the trials & tribulations of Walschaerts valve timing.!
I thought it'd be easy to help the OP as I have a Startrite, as well as an e-copy of their brochure with specs.(PM me if you want a copy). Nothing on the brochure about the depth gauge though.
However, I removed the threaded depth stop bar and went through an extensive collection of old nuts from BSC to metric with a view to finding a couple to send on to the OP. No such luck, nothing fitted BSF, BSW, UNC etc.
My thread pitch gauges didn't help with identification either. It looked metric but if it is, it must be between whole numbers. So herewith an attempt to lure the thread experts into an answer:-

Edited By Fowlers Fury on 21/04/2020 16:45:32

Thanks, FF

... That doesn’t look like 14 tpi to me

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MichaelG.

I hardly dare mention this, but ...

According to RotaGrip, 13.5 tpi is German Conduit Thread

**LINK**

http://www.rotagriponline.com/datasheets/Wiseman/tap%20and%20die%20price%20list.pdf

MichaelG.

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Edit: But, if true, then this Wikipedia page must be wrong

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

... The plot thickens !!

Edited By Michael Gilligan on 21/04/2020 17:27:45

That first list includes a 16 x 1.75mm pitch. Wonder whether we call that nearly standard or nearly coarse?🙂

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Where ?

Rotagrip are incorrect. They conflate the PG number with the thread pitch.

This site is very good in case you have not seen it before:

https://www.gewinde-normen.de/en/pg-thread.html

There is an M16 x 1.75 tap listed on page 2 of the Rotagrip catalogue though.

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Thanks for confirming my suspicion

MichaelG.

In the list🙂 page 2?

Tap M16 x 1.75 £11.38 T1405

My old Startrite floor standing machine, serial number 73698 has a 5/8" x 14 BSF thread, confirmed with thread gauge.

Dennis

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Sorry ... I obviously misinterpreted your reference

Thought you meant the chart posted by Gary Wooding

MichaelG.

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... and they used to think that the camera couldn’t lie

Many thanks for clarifying that.

MichaelG

If you can wait for delivery perhaps the easiest thing to do is get them from eBay. The third listing I looked at offers M16 x 1.75 RH thin nuts in 304, but if want to make your own, a tap is cheaper than two nuts.

Brian G

Since the consensus among those who actually own the machine corresponds with the measurements in the original posting my money would be on 5/8 BSF. The supplied nuts would appear to be wrong, as MichaelG and others suggest.

I never take anything for granted, but I can't think of any reason the makers would have chosen an obscure thread for such a simple device. A call to Machine Spares might clarify the matter as they do list most of the spares. ( I have no connection with the firm, not even as a customer )

Mike.