BSW threads on fobco drill

[GeorgineerParticipant @georgineer]

Thanks for letting us know the outcome, Daniel. It's always appreciated but not always remembered.

As far as some of the other points raised are concerned, I have never come across Whitworth threads in 64th sizes, but Whitworth did specify threads up to 1/4" in 32nd increments. I still have a 3/32" Whit tap hand-made by my grandfather. I tried it and it's horrible, but he obviously needed it for his business.

The only time I have encountered a 1/16" Whit thread was on a feed pump for a model steam engine. The cylinder cover was held on by six hex-headed bolts that size.

Received wisdom from my father, who did an electrical apprenticeship in Portsmouth dockyard in the 1920s, was that the general practice was to use odd-number BA threads for electrical work, but there were many exceptions.

George

[David Viewing 1Participant @davidviewing1]

Thanks so much for that thread table Nicholas.

British made model locos (for instance, Carson) built before 1914 typically use 1/16", 3/32" and 1/8" Whitworth threads. These are often opened out to BA during restoration which is a pity because screws in these sizes are still produced in UK by EKP (No connection – just a satisfied customer). This is important because many models have been stripped during the 110 years of their existence and the first thing to go missing are the fasteners!

Taps and dies for these sizes are also available – try eBay.

German made models (Bing etc.) made before 1914 seem to use a version of BA, although typically not a good fit with modern hardware. For instance the gauge frame in a Bing loco appears to be held in with 7BA, while the axle stubs are threaded 3 BA. These sizes make practical replacements, but there's room for debate about what the threads actually are.

After the Great War BA seems to have been universally adopted in UK, although I've no idea exactly when.

[Nigel Graham 2Participant @nigelgraham2]

Might the German thread actually have been an old metric one, long before these were sort of standardised?

There were German standard metric threads. So I looked it up… No. they start at too large a diameter. The French had a metric thread standard all of their own, too; but by the time of my reference an international metric series already existed*.

BA is actually metric although specified in inch sizes, based on the Swiss, Thury thread; ranging by geometrical rather than arithmetical progression.

So let's have a look at 3 and 7 BA, and 3 and 7 Thury (both by their designation numbers)…..

by O.D (mm), pitch (mm) and TPI (yes, per inch! Probably for lathe-setting purposes.)

3BA.………4.1 0.73 34.8

3 Thury.…4.11 0.79 34.84

7BA.……. 2.5 0.48 52.9

7 Thury…..2.48 0.428 53.13

It looks then as if Bing used Thury threads, which I think arose in the Swiss clock-making trade. Hence the near but not accurate matches of BA to the locomotive's components.

Also, Thury is not a version of B.A.. Instead, B.A. is a version of Thury.

.

*Reference:

Camm F.J. Screw-Thread Manual; Geo.Newnes & Co, London, 2nd Ed., October 1944. pp 139 and 177.

[roy entwistleParticipant @royentwistle24699]

I was apprenticed at one of the largest electrical manufacturers in the country. BA threads were always even numbers.

Roy

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by roy entwistle on 09/06/2023 09:20:44:

I was apprenticed at one of the largest electrical manufacturers in the country. BA threads were always even numbers.

Weren't the screws fixing UK power outlets and light switches to the wall box 3 BA?

Russell

[Nigel McBurney 1Participant @nigelmcburney1]

Meccano thread is 5/32 whit, odd BA was used in domestic electrics eg 13 amp sockets were secured with 3 ba screws,though they have been 3.5 mm since we went mad and took up metric. Imperial typewriters once the most popular typwriter in the uk made in thousands used odd BA usually 1,3 5,& 7 When I started work in the late 1950s 0 BA was no longer prefered,1/4 BSF was used instead.

[Oven ManParticipant @ovenman]

Posted by Russell Eberhardt on 09/06/2023 10:44:34:

Posted by roy entwistle on 09/06/2023 09:20:44:

I was apprenticed at one of the largest electrical manufacturers in the country. BA threads were always even numbers.

Weren't the screws fixing UK power outlets and light switches to the wall box 3 BA?

Russell

No, they were 4BA. and now they are 3.5mm.

Peter

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Oven Man on 09/06/2023 11:38:26:

Posted by Russell Eberhardt on 09/06/2023 10:44:34:

Weren't the screws fixing UK power outlets and light switches to the wall box 3 BA?

Russell

No, they were 4BA. and now they are 3.5mm.

Peter

Well, perhaps they changed from 3 BA to 4 BA later but I am sure they were 3 BA when I worked for an electrical and and electronics shop in about 1960 to 1962.

Russell

[Frances IoMParticipant @francesiom58905]

the screws from the old wall sockets in my house installed early 1980s or prior were definitely 3BA. As were the small countersunk screws holding the faceplate to the body of the Yale lock

Edited By Frances IoM on 10/06/2023 11:22:53

[Oven ManParticipant @ovenman]

Posted by Frances IoM on 10/06/2023 11:20:25:
the screws from the old wall sockets in my house installed early 1980s or prior were definitely 3BA. As were the small countersunk screws holding the faceplate to the body of the Yale lock

Edited By Frances IoM on 10/06/2023 11:22:53

I think we will have to agree to differ. Estimating age of electrical installation this link might be of interest.

Peter

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