Imperial Fasteners

[AvonParticipant @avon]

Hi, I'd be grateful for some advice on where to source imperial sized countersunk and socket head screws to replace some rather worn ones on my v old Smart & Brown Model M Mk 1. If I could confidently state what size they are I know that would help, but that too is proving difficult. The smallest is about 5/32 and probably 32 tpi.

Grateful for your thoughts.

[AvonParticipant @avon]

Renovating an old Smart & Brown Lathe

[Michael GilliganParticipant @michaelgilligan61133]

My wild guess is that those will be #8 32 UNC

What lengths do you need ?

MichaelG.

[noel shelleyParticipant @noelshelley55608]

5/32" X 32tpi is whitworth. or 3/16" bsf. But 32 tpi could be 6 or 8 unc or 10 unf .Precise dimentions are needed to pin this one down !

[DMBParticipant @dmb]

BSW & BSF may still be available from Blackgates/GLR/ maybe even Reeves or EKP. Try Google??

[Michael GilliganParticipant @michaelgilligan61133]

Perhaps I misinterpreted about 5/32

MichaelG.

[AvonParticipant @avon]

Gentlemen, thank you all for the prompt responses, I have been Googling for Britain with only very limited success. I think I'm going to have to very carefully measure the screws (there is more than one type) and post that info – cant do it at the moment as away from home.

Also, I want to get exactly the right threads as a number need holes retapped as they've not been loved and for some the thread has almost been obliterated – I'm hoping I can identify the thread from the relevant screw and work from there.

I'll have a look at the companies suggested and see what I can achieve.

Have a great Christmas.

[Martin ConnellyParticipant @martinconnelly55370]

A tpi thread gauge in your Christmas stocking would be useful. I have sourced screws like this on Ebay.

Martin C

[BazyleParticipant @bazyle]

Shame on you lot not immediately identifying 5/32 BSW as MECCANO normal screw thread – before they succumbed to metrication.

[John CParticipant @johnc47954]

Try Spalding Fasteners http://www.spaldingfasteners.co.uk Wide range and great service.

No connection etc,

John

[AvonParticipant @avon]

Martin, to my shame I do have a tpi thread gauge but the results seem inconclusive! i'm going to spend more time at the bench and carefully assess the tpi and my use of the guage (maybe the ones I have are a bit cheap!).

Bazyle, what a thought – I shall see if I can find any in the loft!!!

[AvonParticipant @avon]

thanks John – they look to be a useful source. I'll give them a call when I'm more convinced of the sizes I need.

[old martParticipant @oldmart]

The threads I have come across when working on the museums Model A are BA and BSF. No unified or Whitworth have surfaced.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bazyle on 20/12/2019 19:30:17:

Shame on you lot not immediately identifying 5/32 BSW as MECCANO normal screw thread – before they succumbed to metrication.

.

Why the shame ?

Are you suggesting that Smart & Brown used Meccano screws ?

… if so, what were the Meccano part numbers for the countersunk ones, please ?

MichaelG.

[HopperParticipant @hopper]

Posted by Avon on 20/12/2019 19:33:29:

Martin, to my shame I do have a tpi thread gauge but the results seem inconclusive! i'm going to spend more time at the bench and carefully assess the tpi and my use of the guage (maybe the ones I have are a bit cheap!).

Bazyle, what a thought – I shall see if I can find any in the loft!!!

One of those magnifying glasses on a stand with a ring light might be in order for under the Christmas tree then! I couldn't get by without one in my workshop. Even the low cost ones work a treat.

[Robin KingParticipant @robinking15611]

It'd be worth emailing Martin Kirsopp at Emkay Screw Supplies with an enquir He's very helpful with odd one off imperial screws etc for machine rebuilds. Web search will find his website and contact email address.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Bazyle on 20/12/2019 19:30:17:

Shame on you lot not immediately identifying 5/32 BSW as MECCANO normal screw thread – before they succumbed to metrication.

Hurrah for Meccano, but is that true? As far as I know Meccano parts are still linked to 1/2" hole spacing and the fasteners are still 5/32". Even though Meccano has been Made in France since 1981…

Being a coarse thread 5/32" BSW is excellent for Meccano but it's unsatisfactory as a general purpose fastener. I know at least one serious Meccano modeller who prefers M4 because they're less likely to come undone due to vibration. For the same reason it's hard to imagine 5/32" BSW being used by Smart and Brown. My guess would be BSF or UNF depending on date, less likely BA.

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Here’s an interesting aside, whilst we await Avon’s measurements and/or photos:

**LINK**

https://www.usmeccano.com/pdf/newmeccanoscrew.pdf

MichaelG.

[old martParticipant @oldmart]

You bunch of monkeys are more interested on your Meccano than my reply stating what threads are actually on Smart & Brown lathes.

[Howard LewisParticipant @howardlewis46836]

The screws may be 5/32 diameter, and 32 tpi, but the Whit are 55 degree thread form, where the UNC 6-32 are 60 degrees, and therefore, not universally interchangeable.

If the thread is BA, it is not 5/32 diameter.

3 BA is 0.161" or 4BA is 0.1417" diameter, and neither is 32 tpi.

I think that Thread Gauges are needed to act as referee.

Howard.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by old mart on 21/12/2019 19:04:55:

You bunch of monkeys are more interested on your Meccano than my reply stating what threads are actually on Smart & Brown lathes.

.

… But you mentioned Model A

The question is about “Smart & Brown Model M Mk 1”

Do you have any evidence that they used the same threads on both ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Howard Lewis on 21/12/2019 19:40:27:

The screws may be 5/32 diameter, and 32 tpi, but the Whit are 55 degree thread form, where the UNC 6-32 are 60 degrees, and therefore, not universally interchangeable.

[…]

.

The near approximation would be 8-32 not 6-32, Howard

… as per my first posting.

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Michael,

Don't rely on my memory!

Howard

[Michael GilliganParticipant @michaelgilligan61133]

No problem, Howard … it’s just there is enough confusion in this discussion already.

MichaelG.

.

Edit: Wikipedia has a handy listing

https://en.wikipedia.org/wiki/Unified_Thread_Standard#Designation

… but the lathe screws will probably turn out to be Whitworth anyway !!

Edited By Michael Gilligan on 21/12/2019 22:19:30

[AvonParticipant @avon]

Gentlemen,

Delighted to have started such an enthusiastic debate !

I have now had a closer look at two screws in particular (thanks Hopper for making me look through other old stuff from my father – a magnifier was found!). The results are as follows:

Baseplate retaining screws: 32tpi with a measured major diameter of 0.1825". The thread gauge actually reads 32G5/32, but 5/32 is too small!

The countersunk screws appear to be 4BA, with what appears to be almost exactly 38tpi and 0.134" max dia.

It is worth remembering that most of these screws/holes are worn so measured sizes are unlikely to match the 'as designed' specs.

Does this help you to help me?

Regards

[Author]

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