doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Making a Purdey Spring

Le Fusil, 'we' refers to anyone here asked to make a part for an old gun. The photos come from the Purdey factory in Acton, where I was last week. Each folded blank provides the material to make three springs.

I am not a gunmaker, nor do I ever pretend to be one. I do run a firm which employs gunmakers and project manages the restoration of guns. In this sense 'we' includes me, as I am often asked to solve this problem for people.

The subject came to mind as I have a Purdey in right now for a new mainspring. I will see they the client gets his gun back with a proper mainspring working perfectly. I do not file the springs up myself, but you knew that, I think you were just being confrontational, or did you have something constructive to add?

I like this forum but sometimes I wonder why it is not more collegiate and less mean spirited than it is occasionally.

Good catch, that is a very interesting photo. Although, I would opine that the machine work we are seeing was all done on a rotary 4th axis mill.

The iron was made from a piece of round stock, and I can see the mounting bolts still attached to the back of the stock where it was mounted to the face plate of the rotary table. I don't see any operations that could not have been made on a 4th axis, but there still may be EDM work yet to do on it.

As a CAD enginneer, CNC programer/operator myself, I have to say this is a fine piece of work. It is more impressive when you appreciate how many scores of hours it takes to bring a project like that to completion.

I do agree with your statement about people need to understand that producing blank parts with these methods is not a negative. There are still many hours of hand work/finishing involved. Creating these semi-finished parts with CNC technology is simply replacing the many hours of wasted time with a hack saw and bastard files. The parts still have to be brought to final dimensions, and finished by skilled workers, like they always have been.

The one potential drawback I will point to, is that it does limit changes, or one of a kind parts. For example with this forend iron, there is a large investment in creating a CAD drawing, CNC program, testing/editing that program, special fixturing in setup if needed...etc. Once all of that is done, to actually make money on that process, there needs to be a certain quantity of parts made to make a profit, or the price of that one part is astronomical, especially when you then think of all the parts that go into the gun, that are made with this process. There is a chance that this can limit creativity on future designs, but that might yet remain to be seen.

But I digress...Thanks for the photos Dig.

Flintfan,

Nice to hear from one that knows, really knows the new technology.

Lately there is a lot of "information" regarding additive pocesses like 3D printing in metal. What I cannot get from these reports is how heat treatable would be, for example, a forend iron made by laser metal sintering. Seeing one single automatic pistol made this way does not answer the question.

If the additive process can yield equal quality parts, then we are in for a new phase. But it is a big if so far and often one gets the feeling that the reports are deliberately overenthusiastic.

As to the cost of CNC parts. It often is worth it simply because the alternative is more costly. At the B.Rizzini factory they were making triggers from the solid with CNC. I asked Moira Rizzini why not use investment casting, and the answer was that casting needs a 5000 piece minimum order, whereas CNC is cost effective for far smaller batches. At the level of totally bespoke items, the cost of the machining, amortization etc is probably weighed against the cost of bringing on apprentices etc. I am guessing that it probably is about equal.

"I like this forum but sometimes I wonder why it is not more collegiate and less mean spirited than it is occasionally."

I agree. Not just this forum, some internet commenters, here and elsewhere, wade in with insults for no apparent reason, often driven by total misapprehension of what was written.

That reminds me of one more thing I forgot to point out. If you look in the background of the photo of the spring blank, you will see the remnant of steel that two action blanks were cut from of using wire EDM. While wire EDM work is slow (probably cutting somewhere in the 30 square inches per hour rate) think of the alternative of forging out a action blank, then using a hack saw and files to get it to that same point, and level of accuracy.

As for the 3D printing, it is not at the level it needs to be at yet for most parts, but like everything else, it will evolve.

I have a vintage Purdey, 1888, that needed new springs. The action was sent to Purdey where they farmed the spring work out to another firm. I got it back and it was not right. Back a second time to Purdey where they did get it right themselves.

My point is that this is a very delicate and hard to forge/machine/file part and I would never attempt to make it myself, nor would my Purdey trained gunsmith, here in the US.

Good point Dig!!! A lot of good people have left this Board or only post occasionally because of that.

Getting back to springs....I have attempted to make a v-spring and for the home gunsmith it seems a mixture of luck and pluck. The hardest part being tempering after the thing is shaped and partly finished. Hats off to those who can do it.

And a Purdey mainspring has a lot of work to do - it has to open the barrels, cock the tumbler and fire the lock.

Unfortunately, the work I do is so varied I really can't make use of all this modern technology. So we do it the old fashioned way.

Here I'm making a new pair of mainsprings for a very early Dickson round action.

First, a suitable piece of steel is sawed off a really big chunk.

http://i1230.photobucket.com/albums/ee496/671RTO9513/Miscellaneous/DSC_1412.jpg?t=1387376579

Then it goes into the mill to be machined to the basic shape. No DRO either.

http://i1230.photobucket.com/albums/ee496/671RTO9513/Miscellaneous/DSC_1417.jpg?t=1387376689

The basic blank is bent to shape.

http://i1230.photobucket.com/albums/ee496/671RTO9513/Miscellaneous/DSC_1419.jpg?t=1387376743

The little anti-friction roller is fitted.

http://i1230.photobucket.com/albums/ee496/671RTO9513/Miscellaneous/DSC_1414.jpg?t=1387376635

Filing the spring to shape.

http://i1230.photobucket.com/albums/ee496/671RTO9513/Miscellaneous/DSC_1422.jpg?t=1387376799

All filed up, and ready to polish.

http://i1230.photobucket.com/albums/ee496/671RTO9513/Miscellaneous/DSC_1426.jpg?t=1387376859

Here is the trigger plate with two brand new springs.

http://i1230.photobucket.com/albums/ee496/671RTO9513/Miscellaneous/DSC_1487.jpg?t=1387376367