Why would the nuts be ME thread on anything not made by a model engineer?

On 25 March 2024 at 23:28 Bazyle Said:

Why would the nuts be ME thread on anything not made by a model engineer?

Maybe they are just 1/2 x 40tpi 55deg Whit form.

EKP did do some ME size nuts, I can’t spot them on their site at the moment but they do have some sizes on their ebay shop so worth contacting them to see if they have 1/2 if they are just basic hex nuts.

Where are you Matric? we need more info.

On 25 March 2024 at 18:44 matric Said:

Hi folks,

I need a couple of 1/2″ x 40 ME nuts, for an old marine compass. I have no experience with this type of things, and no ability myself of making them. By any chance, does anybody have any spare?

Thanks, and apologies for my naivety…

Matt

No need to apologise Matt; nuts, bolts and threads are complicated and the terminology can be ambiguous!

Just in case, please confirm you mean ‘nut’ rather than ‘bolt’, that ME means ‘Model Engineer’ rather than ‘Metric’, and that 40 means threads per inch!

Though not impossible, 1/2″ x 40ME is unlikely on a Marine Compass, so maybe the description is wrong.  Can you confirm the dimensions?

Here’s a drawing of a nut:

Then,

• what’s the diameter of the hole through the nut – the one marked 28.54 in my drawing above.  (Or the diameter of the bolt the nut has to fit, if that’s easier.)   Is this diameter 1/2″?
• what’s the distance across flats ‘AF’, – the dimension marked 53.77 in my drawing.
• How deep is the nut, – the dimension marked as 15 in my drawing

How sure are you the thread is 40tpi?

The nationality and age of the compass may be a clue.   After about 1870 older British and US will be inch based, except British instrument threads are often BA.   Other countries are is likely to use metric threads.   Before 1870, threads weren’t well standardised, so it could be non-standard.     Further, thread standards are application specific, and yours may not be common, or possibly even proprietary.  Gunsmith threads are notoriously non-standard.

This website lists many possibilities, if anyone is interested!!!

First step is to nail down what it is exactly.

Dave

For what it’s worth: According to georgeglazer.com

Sestrel was a British manufacturer of marine compasses. In 1993, the company was acquired by SIRS Navigation Ltd.

MichaelG.

.

Edit: __ largely irrelevant web-page here:

https://www.georgeglazer.com/wpmain/product/maritime-instrument-navigation-compass-

binnacle-sestrel-brass-vintage-london-c-1940s/#

“Sestrel” originated as a trade-mark of Henry Browne & Co. of Essex. As long-time makers of a range of marine instruments it seems likely that they would use various fine threads, almost certainly of imperial form I’d expect.

<p style=”text-align: left;”>I think Dalbiy is correct, the one shown on ebay has 2 shoulder bolts. The nut and bolt on the OP photo is probably just to hold it together temporarily. Having the left hand nut overhanging the dial would be a naff piece of design. Spares will be unobtainable, best approach is to find someone local who can make a copy of the RHS bolt, but we don’t know where the OP is located so cannot advise</p>

If the nut shown is 1/2″ M E, that is a BIG Compass.  Presumably for a sea going merchantman?

Is it intended to act as a locknut, to introduce friction, so that the compass, once inclined, stays at that angle?

Model Engineer threads are Whitworth form, so there should be a little rounding. This will make the bolt thread OD a little less than 1/2″. by 0.16P, or 0.005″, to give an OD of 0.495″

According to Tubak Cain’s “Model Engineer’s Handbook”, the standard pitch for a 1/2″ Model Engineer thread is 32 tpi; so these are “special” at 40 tpi.

The depth of 40 tpi M E thread is 0.016″, so theoretucally the Tapping Drill should be 31/32″ (12.192 mm)  The nut is likely to have a measurement over the rounded crests  of 0.473″, so a 12.2mm drill should isuffice

Without wishing to be rude, it is posible that the OP lacks the facilities, if mot the skill, to make the required  nut, and is indirectly asking if someone will make it for him.

But more information is required, as to the thickness of the mut; AND what size hexagon does he want?  The standard for a 1/2 BSW or BSF hexagon should be 0.820″ ACROSS FLATS, although with a shallower thread this could be reduced.

And, where is he located? Shipping a nut to the antipodes , or to somewhere in Asia, might be an expensive and complicated procedure.

For a marine environment, steel is not likely to be the best material, unless stainless (which may bring its own manufacturing problems)  rather brass or even phosphor bronze.

Howard

On 27 March 2024 at 21:12 Andrew Johnston Said:

On 27 March 2024 at 19:55 Howard Lewis Said:

Without wishing to be rude, it is posible that the OP lacks the facilities, if mot the skill, to make the required  nut

…

 

Excluding model engineering the only common use for a 40tpi thread that I can think of is imperial micrometers. Does anyone know if micrometer barrels are Whitworth form?

Andrew

I don’t know for sure, Andrew … but it would seem eminently logical to me

… the thread-form was designed to be very close-fitting, which would presumably make it reasonably resistant to contamination, and particularly smooth-acting.

MichaelG.

Matt where are you ? Are you sure it’s 40 tpi If you can count 39 tpi in 25mm that would make it right ( or 40 in an inch ) I have brass hexagon so it could be made. I also have a similar looking compass. Noel

Ah! The photo of the nut, rather than the compass clarifies things.

Once the dimensions are clear, no doubt some kind soul on here will make a replacement.

All that will be needed is where to send it.

Howard