Imperial Fasteners

[old martParticipant @oldmart]

You have 3/16 BSF screws if they measure 0.1825 and have 32tpi. And the 4BA looks good, too. Check out these thread charts from Motalia, they can be printed out;

**LINK**

[Howard LewisParticipant @howardlewis46836]

Presumably the 32G5/32 thread gauge is Whit form? 0.1825 sounds like a slightly undersize 3/16 BSF.

4 BA is 0.1417" diameter, and the 0.66 mm pitch approximates to 38.5 t[i, according to Tubal Cain's Model Engineer's Handbook.

Howard

[old martParticipant @oldmart]

You try actually checking the difference between 38 and 38.5 tpi, I would not be able to without a shadowgraph.

4ba and 3/16 BSF repair coil kits are easily available as long as there is enough wall thickness around the hole for the oversize tapping. 

When measuring the od of a male thread, it is always smaller than the theoretical size.

Edited By old mart on 23/12/2019 16:53:00

[Dave Morris 2Participant @davemorris2]

If you are having difficulty sourcing BSF fasteners its worth trying some of the old car suppliers. Most British cars before about 1950 use BSF/BSW. I sometimes get mine from here:

theaustinsevenworkshop.com …there are others..

Dave

[duncan webster 1Participant @duncanwebster1]

If Smart and Brown were a UK company it is unlikely they would have used Unified screws. As at least one screw is BA, is it not likely that what looks like 3/16 BSF is actually 2BA. The difference in pitch and dia is very small, but the thread angle is different.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by duncan webster on 23/12/2019 22:33:12:

If Smart and Brown were a UK company it is unlikely they would have used Unified screws. As at least one screw is BA, is it not likely that what looks like 3/16 BSF is actually 2BA. The difference in pitch and dia is very small, but the thread angle is different.

.

That is very logical, Duncan … particularly as British Standard preference was to use BA for sizes less than 1/4”

The only reason for my original ‘wild guess’ at at UNC was the description Avon gave:

“The smallest is about 5/32 and probably 32 tpi.”

… I took ‘about 5/32’ to mean ‘not 5/32 but thereabouts’

MichaelG.

[old martParticipant @oldmart]

I think Duncan is probably right about the 2BA, it is much more likely to be used than 3/16 BSF, and pretty close in size. The model A has 2 and 4 BA, 1/4, 5/16 and 3/8 BSF threads in steel and cast iron. I don't remember if the headstock is held on to the bed with 3/8 or 1/2 SHCS.

Edited By old mart on 24/12/2019 14:29:31

[AvonParticipant @avon]

Gentlemen,

Many thanks for the advice – I'm not certain that the screw sizes are 2BA & 4BA. I've now cleaned the threads with the relevant taps and things are looking much better.

The help has been very much appreciated.

Hope you all get suitably useful Christmas presents!

All the best.

Peter

[S.D.L.Participant @s-d-l]

Posted by duncan webster on 23/12/2019 22:33:12:

If Smart and Brown were a UK company it is unlikely they would have used Unified screws. As at least one screw is BA, is it not likely that what looks like 3/16 BSF is actually 2BA. The difference in pitch and dia is very small, but the thread angle is different.

Cant see why not, my Mark II colchester Student is UNC / UNF it was a big push in the 60s to standardise on an international thread befire the move to metric.

Steve

[duncan webster 1Participant @duncanwebster1]

Posted by S.D.L. on 24/12/2019 17:09:03:

Posted by duncan webster on 23/12/2019 22:33:12:

If Smart and Brown were a UK company it is unlikely they would have used Unified screws. As at least one screw is BA, is it not likely that what looks like 3/16 BSF is actually 2BA. The difference in pitch and dia is very small, but the thread angle is different.

Cant see why not, my Mark II colchester Student is UNC / UNF it was a big push in the 60s to standardise on an international thread befire the move to metric.

 

Steve

Mk1 was superceded by mk2 in 1948, bit earlier than 1960's

Edited By duncan webster on 24/12/2019 17:32:21

Edited By duncan webster on 24/12/2019 17:33:00

[S.D.L.Participant @s-d-l]

Posted by duncan webster on 24/12/2019 17:32:04:

Posted by S.D.L. on 24/12/2019 17:09:03:

Posted by duncan webster on 23/12/2019 22:33:12:

If Smart and Brown were a UK company it is unlikely they would have used Unified screws. As at least one screw is BA, is it not likely that what looks like 3/16 BSF is actually 2BA. The difference in pitch and dia is very small, but the thread angle is different.

Cant see why not, my Mark II colchester Student is UNC / UNF it was a big push in the 60s to standardise on an international thread befire the move to metric.

Steve

Mk1 was superceded by mk2 in 1948, bit earlier than 1960's

Edited By duncan webster on 24/12/2019 17:32:21

Edited By duncan webster on 24/12/2019 17:33:00

The Mk1 Student with Roundhead with the steel base and tray came in the early 50s and the MKII first Square head came in the 60s I belive.

Steve

[AvonParticipant @avon]

Hi Duncan, I thought the Mk 1 was made until 1956, but I cant find where I got that from. Lathes.co.uk could be read to say that it was no longer produced after 1948, but that would assume the Mk1 and Mk2 weren't available together. I simply don't know, but if you have more info I'd be grateful to know. All the best.

[duncan webster 1Participant @duncanwebster1]

Posted by Avon on 24/12/2019 21:56:30:

Hi Duncan, I thought the Mk 1 was made until 1956, but I cant find where I got that from. Lathes.co.uk could be read to say that it was no longer produced after 1948, but that would assume the Mk1 and Mk2 weren't available together. I simply don't know, but if you have more info I'd be grateful to know. All the best.

I just quoted what I read on lathes.co.uk

[old martParticipant @oldmart]

It's such a shame that the Yahoo groups have just died a death, I would have put the question directly to them. I think it would be a good thing for everyone who has never seen a S & B lathe except in pictures to stop clouding the issue, and refrain from stirring things up. I'm surprised that nobody suggested metric threads, they made metric models.

[Howard LewisParticipant @howardlewis46836]

I thought that the various suggestions were attempts to help by suggesting possibilities, as what the fasteners might be.

Especially since there have been suggestions that threads (Note Old Mart's last line! ) may have changed as the models progressed.

Can Lathes UK, or Tony Griffiths not provide any guidance?

Also, if the machine is at least second hand, it is quite possible that it has been made a hybrid by some previous owner, so that anything may be present, but no longer prototype.

Hope,the hangover is better by now!

Howard

Edited By Howard Lewis on 26/12/2019 18:04:20

[Michael GilliganParticipant @michaelgilligan61133]

Posted by old mart on 26/12/2019 17:52:14:

It's such a shame that the Yahoo groups have just died a death, I would have put the question directly to them. I think it would be a good thing for everyone who has never seen a S & B lathe except in pictures to stop clouding the issue, and refrain from stirring things up. I'm surprised that nobody suggested metric threads, they made metric models.

.

As an alternative, you [or Avon] could contact **LINK** directly.

https://www.smartandbrownlathes.com

[quote] Please also feel free to contact us for any other help and advice you may need on your Smart and Brown lathe. [/quote]

… I am not worthy to do so.

MichaelG.

Edited By Michael Gilligan on 26/12/2019 18:13:23

[AvonParticipant @avon]

I did try contacting Bracehand a while ago but didn't get a reply. If they are operating I would happily share the drawings I'm making of the Model M Mk1 on Onshape.

It would have been a wholesale job to convert the lathe to metric and it would have been a surprise (but not impossible) if it had remained metric. My thinking for this is that the S&M was based on a German Boley lathe which I expect was metric, but since this was shortly after WW2 I imagine the enthusiasm for things metric would have been limited.

For info, I've now cleaned the threads that were causing concern and ordered replacement screws – the sizes were 2BA and 4BA.

[Martin ConnellyParticipant @martinconnelly55370]

Old Mart and Michael G. Smart and Brown Model M Yahoo group has moved to Groups IO.

Howard, as I am not trying to maintain a museum piece lathe I have put 5/16 UNC hex grub screws into the tail stock adjustment positions to replace the original slotted screws that were worn and annoying to adjust. They may have been Whitworth form to start with but the UNC screws fitted without any issues so that's what I used. Proves your point I believe.

Martin C

[Howard LewisParticipant @howardlewis46836]

No problem with an old machine being upgraded.

It is only if you are trying to keep original that it becomes important.

Some designs benefit from later changes, and in some cases current materials /threads are the only way of keeping a very old machine going.

Retaining a thread made by the local blacksmith in 1725 may be prototype, but no one is likely to be able to reproduce a 17/64 x 7.5 tpi thread with a 42 degree form. Unless you want to file it like the originator.

Working 140 miles from home, I needed a 1/4 BSW nut. Only M6 available, but I had a 1/4 BSW Tap. Not over the moon about being non prototype but the machine could be adjusted and returned to service, there and then.

Once I helped someone who had lost a wheel by recovering the wheel and taking one nut from the other three wheels to retain it, for a slow drive to a garage, for a proper fix.

Where needs must the devil drives.

So you have to adapt to the nearest possible equivalent.. In some instances, the original design, even if using "standard" fittings, may not be as good as a later variation. the original may have been a fine thread in Aluminium, but a coarse threaded bush may be less likely to strip.

Remember Trigger's Broom?

Happy New Year to All

Howard

[AvonParticipant @avon]

Just thought i'd share a couple of photos of my newly filed dog pin socket screw – it retains the gear for moving the saddle along the bed. Both the original and the replacement are shown. I heard a similar story to Howard's many years ago – if I remember correctly an expedition to the Duhd Kosi river in Nepal had a problem with a wheel stud – the local mechanic simply filed a replacement which apparently gave good service for the remainder of the exped.

[old martParticipant @oldmart]

The Model A at the museum is certainly not a museum piece, All the modifications and repairs use metric threads as they are easier to get hold of. The only exception is a 3/8 BSF helicoil in the apron where only about 50% of the original thread was left. I even drilled a couple of 8mm jacking screw holes in the saddle as it was a pain to get the apron separated as the dowels are tight. The repairs to the cracked cross slide use 8 and 3mm threads. If I can find the photos for that repair, I will start a new thread on the subject. 

That pic of the screws reminds me of when I was a kid and broke a banjo bolt in the rocker oil feeds of my R E Constellation. It was miles from home in Kent. I took the broken bits to a local garage and the mechanic made me a new one in five minutes by just filing a flat on a bolt, easy when you have a practical mind.

Edited By old mart on 29/12/2019 13:43:49

Edited By old mart on 29/12/2019 13:49:47

[old martParticipant @oldmart]

I looked in Groups I O and found nothing.

[EmgeeParticipant @emgee]

Posted by old mart on 29/12/2019 18:17:24:

I looked in Groups I O and found nothing.

Try this link **LINK**

Emgee

[old martParticipant @oldmart]

Shame it seems to be an exclusive Model M group, not much use for the rest of the S& B people.

[Howard LewisParticipant @howardlewis46836]

On the subject of being up the creek, in this case quite literally..

Many years ago, a there was an expedition, using small hovercraft, up, ( the Amazon, Nile, or somewhere very remote) when they burned a hole in the crown of a piston. A sheet of copper was rivetted onto the crown and the engine reassembled. the hovercraft completed the expedition successfully, and was duly returned to the makers. My friend, who had helped build the craft, still has the piston, I believe!.

Once the lathe is operable, it may be possible to turn a stub on another capscrew as a permanent replacement.

Howard

Edited By Howard Lewis on 30/12/2019 14:09:45

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