New Thompson conversion in progress

WOW!!

first time ive seen this thread,its looking verry good indeed , i know what you mean about re-learning to use a lath and mill but they are the most fabulous toys to own and they help make even more wonderfull toys.verry time consuming ,was going to suggest you get an x y axis bed to extend the throw over the bed as that is on my list for the same reason if i can find a decent one to my budget.keep up the good work.

The problem I have is with the top of the receiver. That's a continuous flat surface about 336mm long - my mill's table is long enough to hold that, but the actual travel is only 300mm. That means I'll have to mill it flat by going across the top with a wide cutter, or move it along when I get near one end. Fortunately, that surface is one of the least critical to get perfect - mechanically-wise at least.

All the other continous surfaces are shorter, so they shouldn't be a problem.

Another update:

Selector Lever

I've made a replacement selector lever for my M1928 that looks like the older type than those on the M1A1. I say "looks like" because I had to change some of the measurements a bit for my tooling and to fit it to the gun.

The original M1A1 black outer parts are fixed to plastic pins which go through the frame.
Those pins are screwed into a small plastic "plate" which is attached to the gearbox. This joint is "keyed" by a D-shape on the end of the pin going into a D-shaped hole on the gearbox part.

Because of the design of the M1928 levers, there's no way to make them 2-part in the same way as can be done for the M1A1 levers. The part I've made replaces the outer part AND the pin with a single piece (See the pic). So the pin part of it needs a D shape on the end.

The selector I've made uses the original screw from the plastic pin.
One "sacrifice" to authenticity is a visible screw hole on the outside. Maybe one could apply some black putty, or something like it, to temporarily fill the hole.
Another is making the lever thick enough to accommodate the screw head.
The screw that's already in there is something like a 1.5 or 2mm dia. thread. The raw metal of the one in the pic makes the black screw more obvious. I might be able to make the screw seat further down, but I might need to get the gearbox out to see how far I can put in the screw.

-- attachment is not available --
The gun's original screw isn't a machine thread, it's a self tapping thread.
Using a grub screw would would mean tapping the lever and retapping the gearbox part. The version I've shown is reversible.

Also, a screw with a head gives you some warning before it comes out.

I think the safety lever is thick enough in real steel to not need to widen it, but it'll still need the visible screw hole.

I messed up the detent hole on the protoype - the drill wandered too much- but it was good enough to determine that the original detent spring is too long for these levers. I'll see if I can find an alternative.

It needs a bit of tweaking. Not least because it only just clears the mag release. That's part of the original design, though.

There has been some interest expressed if these could be reproduced. To that end, when I've finished the safety, I'll look into casting some in white metal.

For cast white metal parts, what I'm going to try is to machine a brass insert to be put into the mould before the white metal is poured, so it becomes part of the lever. The brass part would provide some strength at the point where it's secured to the gearbox mechanism, while still being able to "solder" to the white metal which forms the shaped lever.

Machining that insert would be relatively easy when compared to machining the whole thing.

The white metal might be good enough on its own so an insert might not be needed. We'll see.

YEAH!!!!

Battery "Cunning Plan"

As mentioned in the "Latest acquisitions" thread, I have a cunning plan for fitting a LiPo into the receiver of an M1928 to allow the butt to be made easily removable, as per the real steel, and to avoid using a tiny battery to fit in the space behind the gearbox. I've not seen this idea anywhere else.
This plan will not work in the M1A1 because of the design of the receiver.

The plan is:

Fit a 2-cell "Crane Stock" LiPo with 1 cell either side of the gearbox/cylinder.

This is a photo of the crane stock LiPo I used for my concept test.
-- attachment is not available --
This is the LiPo fitted in my "test receiver".
-- attachment is not available --
The test receiver is one of the "budget gun" receivers modified to fit the Cyma lower. I used the budget gun receiver for the test as it's made of plastic, and so is easy to machine and adjust afterwards with a utility knife.

What I've done there is to machine out of each side a rectangular hole for the lipo cells to fit in, making it long enough for the wires to go past the gearbox end when assembling the gun.

Obviously you need to chose the LiPo carefully - It needs rectangular cells, no more than about 20mm high, 6 or 7mm thick, and 150mm long. There's some leeway in the dimensions, particularly the length, but the height and thickness are critical to get right.

I obtained the LiPo in those pics from here:
http://cgi.ebay.co.uk/FireFox-1200mah-7 ... 230770a8a7
FireFox 1200mah 7.4V Li-Polymer Battery 2-pcs (20C)/KHM

The point of this test is that one of the usual ways to make an M1928 is to put side panels on the M1A1 receiver to pad it to the width/shape of the M1928 receiver. If this is done in the right way, there's enough room to fit the LiPo in that side space. This can be done by cutting the slots out of the M1A1 receiver sides, and making the "padding" sides out of something like 3mm sheet metal, rather than solid.
I used a milling machine to cut the slots in the test receiver because I have one and it does the job so easily. If you don't have a mill, a Dremel-type tool could be used.
It could do with the slot being continued further towards the rear to give more clearance for the wiring.

Having done the test receiver like this, I'm very likely to do this to the receiver I have from a 1928-alike.

I don't think the Mosquito Molds receivers have the sides hollowed out. If that's the case, anyone wanting to do this mod to one of those would need access to a milling machine.

This conversion looks like it's really going well
I'm very impressed indeed!

Thanks, guys.

Aha! Now that is a cunning plan. I'll have to see if this concept can be transferred to my build.

I thought you might like it.