British Gunmakers screw threads

[Dave Ward 1Participant @daveward1]

I have been both a model engineer and part time gunsmith since the mid 60’s.  Over the ensuing years I have made many odd sized screws to fit the various arms that I have repaired.  British gunmakers like BSA and Parkerhale had a series of odd screw threads.  From what I have observed they were of the whitworth form.  From all of the literature on arms manufacture and gunsmithing, I have never seen a list of this seemingly odd thread system.  Can any of our readers help please?

 

Dave Ward

Nelson

New Zealand

[Dave Ward 1Participant @daveward1]

[Ian HartParticipant @ianhart94481]

Hi

 

Sorry, I have no helpful information for you, just thought I’d let you know that the rifle in my photo album is a BSA Sportsmatch 5.

Although one of the screws, that holds the trigger to the action, I believe is BSF.

 

 

Ian Hart

[Dave Ward 1Participant @daveward1]

Thanks Ian,

Thanks for the photos, rifle looks great.

Yes the thread system is something that fascinates me.  I’ve measured and cut many.  All seem to be very oddball with respect to diametrical size and potentially pitch.  They don’t seem to fit the BA, BSA, Whitworth, UNF, UNC, or metric as we know it, thread systems.

 

Cheers

 

Dave

 

[David Clark 13Participant @davidclark13]

Hi There

I used to work for a company called Wilcox And Gibbs.

They made industrial sewing machines.

They were an American company and they had their own system of threads.

They were letter threads and the one we used most often was the letter N one.

It must have been about 6BA size.

regards David

 

[Dave Ward 1Participant @daveward1]

Hi David,

Thanks for the info.  I’m sure that sooner or later someone will come up with a list of threads.  There must have been a system, different from anything else that I have come across.  Over the yeas I have cut too many of them to believe that the screws I’ve made are one-off’s.  The diameters are definitely off standard size, often close to some 64th.  Also the threads seem to be nothing which related to the English/American systems at least according to diameter vs pitch.

[des bromilowParticipant @desbromilow43838]

For what it’s worth, MOST of the old BSA firearm screw threads were 26tpi because their threading tools were used on the bicycles and motorcycles.

 

I cannot speak on the modern BSA parts, but the old ones I’ve worked on (WW1/2 and up to 1960) have been 26tpi for anything smaller than 3/8″ od.

 

Hope that helps,

Des

Oz

[mgjParticipant @mgj]

I was told that much of the rifle tooling was transferred to Pakistan – sold to whom I don’t know. However you can  get spares for the CF2 series (I needed a magazine floor plate and spring for a .270) and quite possibly the Monarchs. Pakistan was where it came from. So a web search in that direction might turn you up a catalogue or parts listing?

 

Sorry I cannot be more specific.

[MikeParticipant @mike89748]

Hi Dave,

In the days when most guns were hand made, most individual gunmakers had their own threads. Male threads were struck by hand in the lathe, and they made their own taps. As a consequence, on very old guns you will find some really weird threads! Not very helpful to you, I’m afraid! – Mike George, Technical Editor, Sporting Gun Magazine

[John BurridgeParticipant @johnburridge26484]

The thread for bicycles I believe were set up as a standard first by BSA most of the threads being 26TPI,This then got accepted by CEI (cycle engineers Industry)which evolved into the British standard for cycles BSC.

Most of the threads except for Headsets and bottom brackets which used the 24 TPI range and the 9/16" X 20 tpi which is the grenral pedal thread.

Strangely enough the Italian Campagnolo enlarged the wheel spindle threads from 5/16"(8.00mm)X26TPI to 9mm and the Back spindle thread from 3/8"(9.5mm) to 10mm so that is why you get metric outside diameter with a british Teeth Per Inch (TPI)

Regards

John

[Nick_GParticipant @nick_g]

.

I can tell you that the small sound moderators are all UNF 1/2 x 20, be it manufactured by Parker hale, Sako etc, etc. – It's kind of an unofficial industry standard.

Nick

[Oompa LumpaParticipant @oompalumpa34302]

And a good number of centre fire moderator threads are 5/8" UNF.

graham.

[Nick_GParticipant @nick_g]

Posted by Oompa Lumpa on 03/05/2014 20:43:16:

And a good number of centre fire moderator threads are 5/8" UNF.

graham.

Yes I agree.

Both my 22/250 and the 25-06 are so. But they are heavier barreled versions. A 'standard' weight barrel at 5/8" may leave not a lot of shoulder for the face of the moderator to mount to.

Nick

[Dave Ward 1Participant @daveward1]

Hi all,

Since posting my first request re gun makers screw threads, a good friend provided me with the following site

**LINK**

This lists the threads used on nearly all of the British military rifles made by BSA at Enfield. For those of you that have an interest in such things, the list makes interesting reading. It screams of trade protection, at least up until WWII when the gun makers began using the BA thread system. The older screws were very odd diameters. Likewise the thread pitches are certainly interesting and some would be a challenge to cut. I would assume that BSA made most of their own tooling, as I recently acquired several profile milling cutters with BSA marked as the maker.

[Stuart BridgerParticipant @stuartbridger82290]

Dave, Very interesting post, I see a lot of the 26 1/3 TPI which is still used on most gun cleaning rods

Stuart

[JonParticipant @jon]

The term gunsmith thread derives back from the days when there was no industry standard.

When any thread was made it was by either that individual or company and liable to change with those subsequent parts, hence the term gunsmith thread meaning it could be anything. Many a time had to make a die to cut a male tap so that original female thread either cleaned up or deepened with extra thread. Some of the threads can be really crude as in filed in by eye forming a female thread in the part.

Quality manufacturers today still use a mix of BA, UNF and BSF.

Barrel threading unless specified is usually done a UNF pitch, though an ever increasing 1mm pitch is available good enough for .338 Lap with spigot behind.

[Brian WoodParticipant @brianwood45127]

I have tried posting a table of gearings for Myford ML7 lathes with gearbox to cut these odd threads, but it was too long to post in one piece and I thought it would lose impact by being broken up.

If anyone would like a copy please send me a message with your email address.

Regards Brian

[Dave Ward 1Participant @daveward1]

Hi Brian,

Thanks for the offer, yes I would like a copy, as it saves me working them all out each time I need one. My address is *@*.

Thanks again.

Dave

Moderator's advice: Please use PM's to exchange email addresses.

Edited By Neil Wyatt on 08/05/2014 10:00:41

[Brian WoodParticipant @brianwood45127]

Hello Dave,

I tried to send them but your email address couldn't be found; I did a 'copy and paste' of it so the fault is not one of incorrect transcribing, so please check it.

Regards Brian

[Dave Ward 1Participant @daveward1]

Hi Brian,

What I sent is correct! If you would be kind enough to post your address, I'll try the reverse.

Sorry about the glitch.

Cheers

Dave

[Brian WoodParticipant @brianwood45127]

Hello Dave,

My computer didn't recognise it for some reason. We'll try the reverse coupling—

wood_y@btinternet.com

Regards Brian

[Author]

Posts