Rifling cuts

[don311]

Anyone know how the rifling on the No 4 Mk2 and the No 5 JC were cut? were they Machine cut or button cut?

Information

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[Bruce_in_Oz]

I have never seen information on production methods on a drawing for a SMLE barrel.

References to numbers for rifling tools for SMLES; yes, but actual production method documents, no. There is no mention of the actual rifling METHOD in either the 1903 or 1938 specification documents.

An interesting note about rifling on Australian drawing A.658 (WW2 vintage barrel drawing) is this:

"Note:

As alternatives, a barrel having TWO grooves diametrically opposed or FOUR grooves equally spaced would be acceptable"

This drawing dates from when it was redrawn from S.A.I.D 1318G, 18October 1944. On 29 September 1947, there was a minor change to one of the dimensions of the flat on top of the Knox form.

But I digress:

My "best guess" is that the principal method in the UK would have been via multiple passes of a hook cutter. This is 17th century technology, but it WORKS and some of the best current match barrels on the planet are still produced by this method.

As for North American production, I also don't know. "Buttoning" didn't really get going until the mid 1950s, when the technology to grind the Tungsten Carbide buttons was refined.

Another approach is "gang-broaching". This uses an incredibly expensive tool which cuts all the grooves simultaneously.and does the entire job as it is pulled through in one pass. Basically it is a long bar with sets of incremental cutters set at intervals and on the pitch of all the grooves. If you need to make a hundred thousand cut-rifled barrels in a hurry, gang-broaches are for you.

Interestingly, in the L1A1, there is allowance for cut and "cold swaged" {hammer forged) barrels. It is the combination of final dimensions and thermal stability that really matter. Because of their process, buttoned or hammer forged barrels are better for hard chroming as there is (generally) a finer surface grade on the lands and grooves after rifling. Late production Lithgow L1A1 barrels are generally hammer forged. These can be identified by "BCF" stamped on the left-side driving-flat at the rear of the "knox form". By "late", I mean 1981. "B" indicates 4-groove rifling and "CF" means cold-forged. In these barrels, the chamber was also formed in the same pass as the rifling. This latter practice is also used in the production of Steyr AUG barrels and has its origins in the need for rapid production of MG42 barrels in the last great global unpleasantness.

[Peter Laidler]

In a word, they were machine cut, right through UK production although I can't say for what you foreigners did!

From my understanding of Fazakerley production, the workforce would not accept ANYTHING remotely modern or up to date To even attempt such a task would have brought about even greater global unpleasantness than described by Bruce!

[Warren]

Attachment 37038Canada cut rifling using a gang broach...these are two rifling broaches from LongBranch Canada.
The broaches and are approx. 20 inches long were pulled through the barrel with each ring of cutters successively larger than the preceding cutter. One pull per barrel.

[breakeyp]

A dirty secret about engineering drawings is that production part drawings give sizes, shapes and dimensions with tolerances but hardly ever discuss that methods used to get there. Product engineering does not care how the parts are made as long as they meet the drawing requirements and the included material and performance specifications. In some cases a forging drawing is also prepared to show what the forged part should look like before final machine cuts are made to take it to size.

The manufacturing engineer takes the drawing and considers what tools he has and what he needs to buy to make the part and what fixtures will be made to hold the part for each machine. He generates a process flow chart that takes the part from raw material to a finished part, indicating what machine is needed, fixture and machine time. And yes each blames the other when the wheel comes off the wagon.

[Peter Laidler]

Was that the wartime process Warren - or postwar. Just seems a trifle 'modern' for wartime production which was archaic even by 60's standards

[bigduke6]

The link below is one of the best "short" articles regarding the barrel process, but regardng the initial question am sure the machines in question were button rifling machines and later used the gang broach (shown in Warrens post) or could be the other way round.

http://www.border-barrels.com/articles/bmart.htm

[Bruce_in_Oz]

Yep, the secret is in the "production books" put together by the production engineers.

In the "old days" these described in mind-boggling detail, each set-up, each fixture and the tools and tool instructions for each cut, and very importantly, the SEQUENCE of each cut/grind etc.

In the case of SMLEs, almost EVERY cut was made on a separate machine. The part would be in a fixture and would stay in that fixture as it was passed from machine operator to machine operator with a gauging / inspection in between each operation. EVERYTHING was made this way. Have a close look at a Garand receiver and be amazed! The radiused guide-rails for the cartridge lifter inside the magazine/clip well are a thing of beauty.

It was TRW who introduced "modern" techniques (not quite CNC, though) to the M-14 production system.

Some modern machine setups include CMM (co-ordinate measuring machine) probes in the system so that the component is measured as things proceed. This enables the machine to adjust for tool wear on the fly.

It's a long way from overhead-belt drive and trays of individual gauges.

[Warren]

Was that the wartime process Warren - or postwar. Just seems a trifle 'modern' for wartime production which was archaic even by 60's standards

I'm assuming late war time as the broaches had a date on the tag when I got them. They walked out the door during the later part of the war (so I was told) and sat for years in a shop and then came to me. I have had them for probably 40 plus years. I think he said they came from the Bren barrel line...but would not bet the farm on it. The mind is the second thing to go.
I also got a handful of trepanning drills (barrel drills) with the broaches as well and will also try and find those.

[Peter Laidler]

That's right about the production engineering side of things Paul, Bruce, JM et al. The production engineering graduates will admit that it's almost a hidden science once they leave uni! My pal is one and to be honest, they talk a different language! They certainly look at things from a totally different perspective............