Am I missing something!

For those in the anorak seats, I found the included angle of the thread on a No1 Bolt head:
79 degrees, 30 Minutes. It is depicted as a triangular thread with notes and tolerances for the form of the root and crest. There is actually a "Go" and "No Go" gauge, both of which are "adjustable to master "plug" gauges by means of a (lockable) screw, not unlike as found on thread dies. NO CMM gizmos in those days.

This is taken from Lithgow drawing C 4983, dated 20 October 1944 which has, hand-written across it: "Superseded. See Data Sheet DS 464, Sheet 410-3-52". This was, in turn, a revision of a 1935 version of the drawing.

Thus, Lithgow fine-tuned some gauging in the process of doing the last ever run of No.1 Mklll* rifles at the factory.

Sadly, i do NOT have this later drawing in the "crypt".

Quote:

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Originally Posted by 5thBatt

I have never heard, read, been advised or seen it being advised or needed to do this myself, i dont get what you're saying here!

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I think what 5thBatt might mean here is that one does not run across that many swivel screws that are so heavily staked that they ruin the threads of the outer band upon removal. (?)

OK. did a bit of ferreting:

The thread on No1 screws for front, rear and piling swivels is:

0.1875" x 33TPI, "Enfield" form.

On the No4 series, post "Trials", this changed to 2BA and stayed that way to the end of .303 rifles in Brit / Canadian etc, service.

POST WW2 in Australia, there appears to have been a shortage of the "special" screws, because there was an "allowance" to use 2BA screws, with the original thread "tapped out" to suit. A couple of years later, widespread distribution of the L1A1, saw the end of that requirement.

Not sure how such a screw shortage arose, as the requirement for their relatively frequent exchange had existed since Day one in service. I have seen a considerable number of them, mint, either in little packets or, more commonly, in jars and tins, and liberally slathered with preservative grease, in various "collections" / sheds around the country; apparently bought as "scrap", post WW2.

I found a few spare and "pre-abused" steel outer bands in a goodies box here, TWO of them have VERY shabby, almost-gone female threads where some bozo has cheerfully wound out the screw without carefully drilling out the end as originally required. there is also a similarly-butchered brass one on the bench.

In the grand schemes of military ordnance systems, this stuff is peanuts. To hard-done-by collectors and shooters, it is a PITA.

How many No 1 fore-ends have been trashed by "enthusiasts" trying to remove the butt first?

As with any valuable equipment: get the manuals out of the trash bin and READ them before wading in with the gas-axe and angle-grinder.

Or Bruce join a place like this and learn from the personnel that have the acquired knowledge to impart to others as you say to many wannabe's just rip stuff apart without first studying how to.
Like yesterday trying for the life of me on how to get the middle fairing off my Repsol 1000RR Honda owners manual p*ss poor dia's and instruction you tube got a flat tyre was as good as an ashtray on the bike I worked around the issue but will need to get them off eventually to do engine work.
There was one push pin located in an area inside the faring near the top radiator that you'd need a 2" mechanic (Leprechaun) to hop in there to get to it there was some pretty choice words coming out the shed I can tell you..........

Yep, Cinders; that is why I haunt places like this and quite few other; swapping information, scrounging electronic copies of user and service manuals for reference, paying back when I can, making contacts in all manner of places.

I reckon it is fair to say that everyone who pops up on these discussions has knowledge and experience to share; whilst they are picking up stuff learned by others. As a kid, I grew up with a wild assortment of .22RF and air-rifles around the neighbourhood. By my teens, I had graduated to Martini Cadets and Lee Enfields. Having a father who was not "just" a motor mechanic, but an ex Army motor-mechanic, serious vintage and veteran car buff, and quite handy with various welding and machining techniques, certainly helped with "approach" to good information.

Where did the Instructions for drilling out the old screw come from? It makes sense, but I can't find any reference to it in the Instructions for Armourers, just a note to not get too aggressive when staking the screw to prevent stripping the threads on removal.

Ideally, you do NOT need to wallop the screw very hard to "stake" it, however.....Murphy was an optimist.

Drilling out the screw ends may be a peculiarly Australian thing, (something about bigger hammers??) or BECAUSE of the prevalence of BRASS outer bands on wartime production rifle from Australian production rifles. If I can find detailed pre-WW2 instructions, they may provide the answer. The very fact that I have examples of what happens if the screw end is NOT relieved before removal may also indicate something. The steel in these bands is quite soft.

So far, I have found:

WEAPON D 113
Issue 1, Sep 76 (note that date!)

In the text is this:

Securing of Screws

10. To minimize the loss of screws the following action is to be taken:
a. After the screws have been securely tightened in the trigger guard front and the spring bolt locking, the metal of the component is to be lightly expanded into the screw slot by means of a centre punch.
b. Securely tighten the screw in the swivel and slightly expand the hollow point of the screw by means of a centre punch.

No mention of screw removal. HOWEVER, good "tradesmanlike" practice would indicate the desirability of relieving the staking before backing out the screws. A few twists with a sharp drill-bit in a basic hand-drill does the trick. You don't need a J-series Bridgeport.

Do any other Kung Flu Kampers out there have copies of Pre-WW2 Brit, Canadian or Indian "workshop" instructions that cover this topic?

More document-diving required!!

The saga continues:

“Instructions for Armourers, 1931” (Brit issue, War Office 30th September 1931), Part II,SMALL ARMS, Chapter 1, RIFLES, Section1- Stripping and Re-assembling, Section 14 (iii), states:

(iii) Swivel screws – With the screw head supported conveniently, expand the hollow point of the screws, by means of the centre-punch, sufficiently to prevent them from working loose. The expansion must not be overdone, as this will cause damage to the slot when stripping.

“SLOT"?

So, a reference that implies that the screws, IF correctly staked, may be removed without “drilling out” to relieve the conical staking.

I cannot find anything (yet) that specifies that the “old” screw is to be “re-used”. Backing it out might be “easy”; getting it started again for reassembly might get interesting.

And that shows I should have read the 1931 copy more closely - it does indeed only mention stripping the slot, not the threads. If it was going to mention it anywhere, I would have assumed it would be in Part II, Chapter I Section 1. But it dosen't mention any special steps to take when removing those screws.

Possibly the drilling out is a post-service measure taken to counteract over-enthusiastic amateurs who heavily staked the screws? I can't think of any band or swivel screws I've needed to drill out and they've all gone back in without issue, and the threads in the barrel bands were fine. You might be on to something with it being Australian as well, I've only encountered a couple of the brass bands.