Thread: Lee Enfield No. 1 Mk III striker screw pitch
Retrieved: 06/07/2014

Does anyone know what the thread size is for the screw that captures the firing pin on the back of the cocking knob of a Lee Enfield No.1 Mk III?

I had to drill this out and would like to run a tap through to clean it up.

Marstar Canada - Striker Screw (LEE-053)

Alan de Enfield
02-01-2014

Screw, Striker, Retaining = 0.144 dia x 37 tpi

It is what is known as an Enfield Thread, unlikely that you will find any taps / dies for these threads.

sp00ky2
02-01-2014

I tried an 8x36 tap as it looks as close as I can get, but no go.

Bruce_in_Oz
02-01-2014

EVERY thread on a No.1 (SMLE) is either an "Enfield" or "trade" special.

It's not just the pitch or diameter: Enfield had their own ideas about the form of the thread. Even the stock bolt, whilst VERY close to a 7/16" 14TPI Whitworth, has a "special" thread form.

The stock bolt for a No.4 is essentially the same as for a SMLE.

The breech threads on SMLEs and No.4s have the same pitch and the same nominal diameter. There it ends; No.4s are Whitworth form, SMLEs are VERY Enfield.

However, EVERY other threaded fastener on a No.4 is either BA, BSF or BSW. This actually helped immensely in the rapid buildup of wartime production; there were thousands of small and large engineering "shops" that already had the tooling to make screws. In WW1, a lot of effort was expended in supplying the special tools and gauges to make the same items for SMLEs.

The Mk6 / trials No.4 were built using mostly the old SMLE thread system, hence all of the drama about keeping them separate from "real" No.4s when things got lively.

P-14s are full of "Enfield specials" as well. That must have been fun for the American manufacturers who were well on their way to their own "unified" thread system. It was the automotive industry / SAE that drove the standardisation case very hard.

From a logistics / armourer's perspective, all of these odd threads are (up to a point), a blessing in disguise. Only "proper" fasteners will fit and work as prescribed. Thus, there is somewhat less likelihood of some enterprising digger replacing a missing screw with some pierce of crap from the local bargain store.

Peter Laidler
02-02-2014

In our last EMER's for the No1 rifles still in service, dated in the late 50's or early 60's as I recall, there was a list of screws/threads in the No4 rifles that could be adapted from standardised BSF's/UNF's/BA's by cleaning out with a tap or die. But I don't seem to remember the screw striker being there.

If the screw thread in yours is totally sha... er... knackered spooky, tyhen you could use a No4 striker and cocking piece as they interchange as a set.

breakeyp
02-02-2014

And to stir the pot with additional useless information, US manufactured arms from flintlocks to the end of the trapdoor Springfield .45-70 use French developed thread sizes. The US bought tooling from the French for the Charleville flintlock and things progressed from there. The older Dixie Gun Works catalogs had two pages on Turner Kirkland's investigations into this interesting area the arcane.

Bruce_in_Oz
02-02-2014

As the old saying goes:

"That's the great thing about "standards"; there are so many to choose from!"

Peter Laidler
02-02-2014

Originally Posted by Alan de Enfield
Screw, Striker, Retaining = 0.144 dia x 37 tpi

4BA is close. 0.142 dia x 38.5 tpi. Since the thread is sharper, 4BA will probably work quite well to clean up a striker screw thread, which is only about 1/4" long. Just use "two finger" torque, no wheel-brace stuff!

If you are unfortunate enough not to have BA equipment, then 6x36 would be next best. 8x36 is far too thick!

Peter Laidler
02-02-2014

Now you mention it Patrick, I seem to remember that the 4BA was used to clear out the No.1 rifle sling swivel screw holes to enable No.4's to be used.

Bruce_in_Oz
02-02-2014

That bit of "creative" engineering; using a BA screw to replace the sling swivel screws continued in Oz until the last SMLE snipers and No.2 .22 trainers went out of service.

The screws are SUPPOSED to be staked into final position. In order NOT to destroy the thread in the outer band, the "staking" had to be carefully removed using a suitable drill-bit. Notice that the proper screw has a small "cup" on the threaded end. This is to guide and steady the centre-punch as it is being whacked with a large hammer. It also provides the alignment for the drill-bit used to cut away the flared end. Failure to remove the resulting flared out end of the screw before removal will result in a destroyed band.

EVERY time a rifle was given a proper inspection or detailed examination by an armourer, that little screw was removed so that the furniture could be removed. It was also a requirement that the replacement screw be staked in position.

As near as I can discover, it was the ONLY screw that got this treatment and thus was consumed in fairly large numbers on an annual basis.

Several other screws are to be staked, but usually by spiking component metal into the end of the driving slot.

These days we have LOCTITE.

Bruce_in_Oz
02-03-2014

The silly thing is that it has never been easier to make all of those weird old "Enfield Specials".

A while ago I got a batch of trigger screws made for BSA "Martini" Cadet rifles. The friendly folk at my local CNC shop simply loaded in the appropriate pitch data and ground some suitably-formed threading tools and away they went.

MLM cutoff screw - 49TPI,
SMLE front nosecap screw -33TPI,
SMLE screw, rear, triggerguard - 37TPI,
SMLE Front handguartd cap screws - 56TPI, It can be done!

Just not in "penny packets" at a sane price.

Then there's the absolute classic: The "Bolt" (Latch) and associated "Nut, bolt, mild steel"for a P-07 bayonet: 0.101" x 26 1/3 TPI. Now THAT is a REAL "Enfield Special". See Spec No. 2123.

Patrick Chadwick
02-05-2014

Originally Posted by Bruce_in_Oz
0.101" x 26 1/3 TPI. Now THAT is a REAL "Enfield Special".

OK, I pass on that one! Diameter is near enough the same as the US "3-" size, but the pitch is extraordinarily coarse. 2.6x1mm would be workable, if there was such a size.

BTW - for anyone in the situation of having to apply such approximations - always use mild steel screws, not tough machine screws, working them (well greased) in/out/in a bit more etc. The screw should adapt itself to the rifle, not the other way around!

N.B. this site http://freespace.virgin.net/j.frankl...read-table.htm Gives the stock bolt as 7/16 BSW, not an "Enfield funny". Although the site has been updated in recent years, with a couple of BA substitutes now being listed, I have a "pre-update" printout, and it was then also listed as 7/16 BSW.

Bruce_in_Oz
02-05-2014

Found it!

Drawing C-633
#81 (Parts list reference) BOLT, STOCK

14 Thds. per inch. Enfield Standard.
Major Diameter: 0.4375" -0.003"

Well, my trusty, German-made "Bokor" screw-pitch gauge tells me that all of my SMLE stock bolts are, indeed, 14TPI and that the thread form appears to be pretty much Whitworth.

So, maybe "Whitworth" WAS the "Enfield Standard" for that one screw. (Tap- dances quickly away to make a cuppa...)

Also found in the same box: a different stock bolt. A whisker over an inch longer than a No.4 stock bolt, it has the exact, same thread on it, along with "EFD" and a "broad arrow" stamped on the head, either side of the driving slot. It also has the "waist" in the shank, to prevent seizure in the wood from swollen timber or corrosion, just like a "proper" SMLE stock bolt.

Martini or early LE / LM?

Homer
02-06-2014

Bruce there are still good supplies of nosecap and trigger guard screws avaiable in Australia.

Bruce_in_Oz
02-06-2014

Homer, I doubt most enthusiasts do a proper, military standard, annual inspection on all (or any) of their goodies, so demand for "consumable" parts would be low.

Those in need in Oz can get most things "Lee Enfield", apart from furniture, from Alan at Kingaroy Firearms.

Parts for large and small frame Martinis are a different matter.

The one category that WILL cause problems for those shooting these critters is SPRINGS. High Carbon steels and "malleable cast iron" age and become brittle. Owners of Sniders and Martinis (and early LM & LE rifles), take heed. Martini Cadet striker springs and the split takedown pin in the BSA/"Francotte" variants fail quite regularly these days. I have also seen more failed strikers lately.

Given that many Lee Enfields are almost as old AND until the advent of the No.4, used ONLY carbon steels, (NO alloy steels allowed, as per original specs), ...Coming soon (well, in the next few decades) to a gun safe near you.