No1Mk111 Receiver Holding Fixture

[tbonesmith]

Hi Gents,

I was hoping one of you may be able to assist me. I'm looking for some ideas for a receiver holding fixture for the No1Mk111.

Ideally I want to hold the receiver in a jig, in a vice so I can perform milling operations. All operations will me external and as I'm writing Im thinking maybe the best solution could be a close fitting mandrel in the boltway, threaded for the receiver threads (like a receiver truing/facing mandrel) held in a dividing head, supported at the other end with a dead centre. That would give pretty good control for orientation and probably enough support for light milling.

The only downside to the mandrel idea is that the barrel must be out, and I would prefer to perform the intended operations with the barrel in, after rifle setup and range testing.

Anyway any images, experience or ideas would be gratefully received, and faithfully applied.

Information

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[mike1967]

Gday Tom,

Im no engineer, but my feeble brain would be thinking, Close fitting Mandrel, screwed up through the mag well, and utilising the main screw and trigger guard screw as attachment points to some type of base

[Peter Laidler]

Although it didn't involve me directly, the team investigating the proposed conversion of No1 rifles to DP spec decided that after several trials and tests that there were really no exterior planes that could be RELIABLY used as datum surfaces across the board. They decided that the only TRUE datum that they could use for machining was the line of the bolt in the body. Even engraving the body with the DRILL RIFLE L60 A1 (later changed to L59A2) was virtually impossible unless EVERY rifle was jigged and set-up individually!

I would accept that the external diameter of the barrel was exactly concentric with the bore (not always guaranteed either.....!) and use a split tapered ring clamp around the nocks form and a centre bored into a tight fitting alloy plug driven into the rear of the bolt-way as as near perfect as it gets. Quite HOW you incorporate these features into a clamp pl;ate to stabilise the body for machining, heaven only knows. But guess what Tom............? You WILL do it........

Using the trigger guard screw weill certainly damage the hole and thread if the body is clamped or held there during machining I fear. The material is really archaic in metallurgy terms

Vive la Belgie

[Bruce_in_Oz]

Are you using something like a Bridgeport or a milling attachment on a lathe?

If the latter, and you don't want to remove the barrel, you "could" grab the muzzle in a 4-jawed chuck and have a LONG mandrel / bar that runs through the body and into the chamber and which has a "centre" hole bored in the "rear' end..

Depends on exactly what sort of milling you are contemplating.

Alternately, align the barrel / body assembly between suitable centres and then attach a couple of "cats" which, after centering, will run in fixed steadies. Use a face-plate and dog to drive the barrel and a flat plate attached to one of those nifty "convertible "live' centres to stop it drifting about.

One way to minimise movement during milling is to take a lot of very small, very fast cuts: I have used a high-speed (30,000 RPM-ish) die grinder and Tungsten Carbide cutters / burrs. Requires minuscule but CONSTANT feed force, is VERY noisy, but if the workpiece is locked up solid and the grinder is also firmly mounted, the process leaves a very clean finish. MANY years ago, I did a batch of "conversions" to several scruffy Garands; sleeving and re-cutting the chamber (alternately setting the barrel right back and re-chambering / threading), opening the bodies up to take M-14 mags, cutting away the mag bottom in the trigger housing, shortening the op rod, etc. etc, not unlike how the Italians (and Indonesians) made the BM-59. 1/4" carbide tools running at 30,000 RPM sliced through the heat-treated 8620 steel like it was butter. Cutter "chatter" was invariably fatal to the Carbide tools.

[bigduke6]

Tom, the only thing that springs to my mind is a mandril with tapped holes to pull it down with screws which go through a plate the screws being vertical and passing though the mag well area, the plate also incorporating a clamp ( similar to an action wrench) at one end which the bottom half is permanently attached to the plate and the top half screwed down to this, also at the other end of the plate having something similar to the draws on a fore-end....

I,ll try and get a drawing up next few days, but if you think of a short Steel type of fore-end, a clamp at the breeching up ring, a mandril fitting through the bolt way and being pulled down with decent screws vertical though the mag well area could extend the mandrill and pull down at the rear also.

[CINDERS]

Can the rear stock bolt hole be incorporated into the mix or were the tolerances on the angle etc to generous it is big enough to withstand the stresses then using the front screw for the trigger guard for the other attachment point also just a thought from a non engineering type person

[Homer]

This jig has worked well for me in the past. Its also held by the front trigger guard screw not shown. There would be ways to improve hold down strength but I haven't found it necessary and repeatability has been very good.

sorry for the **** photos

[Peter Laidler]

We really need to know what you want to do Tom. If it is to, say, mount telescopes on 30 rifles in an identical manner....... OR machine 300 identical DP bodies (as we were charged with doing) in effect run a production line where they're all identical, then you have a problem!¬ Because you HAVE to find holding points that are identical in EVERY body. And with sooooo many manufacturers with allowable tolerances and (dare I say it.....) poor quality assurance you won't get it. The only things you DO know that are identical across the board are the bolt-way and the two horizontal edges across the rear of the bolt-way before the bridge charger guide.

Even the lower apparently straight edged ledge around the bottom of the magazine opening is not either accurate nor constant!
WO2 Ian Xxxxxx who was running the DP NO1 project abandoned the idea and gave them all DP No4's! I know/realise that that's the easy way out, especially when you have zillions of No4 alternatives.

So the question is this. Do you just want a jig to hold the body steady OR do you want a jig to hold EVERY body identically in every axial plane

[tbonesmith]

Hi Peter, I have a couple of No1 Sniper builds to do. And I'd use it in future for the odd job drilling and tapping for a conventional bridge mounts and Field mounts.

If it wern't for the sniper builds I wouldn't bother, but the sniper builds require much more positive and controlled manipulation of the job, and the capacity to rotate the job about the bore axis with precision and repeatability could be very handy.

[Peter Laidler]

You just gotta go with the axis of the bolt which is important in respect of fitting telescopes because you KNOW that the axis if the bolt is (? or VERY close to) the axis of the bore.

How you do it without unbreeching is....., phew!