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

I asked a question. It wasn't loaded. When I post, I usually do have something constructive to add. I did not know that you didn't file up the springs yourself, hence why I asked the question in the first place. You do say "we"a lot and in this country that usually means that you are actually involved in the work, not just acting as a subcontractor farming out the work to the trade. In that case we say things like "a client of mine has a broken gun, so I found a gunsmith to fix it."
Anyway thanks for posting the pics. It is interesting to see these springs made. I've seen Purdey mainsprings made by Alfi Galifent, they are beautiful and complicated. He used to make springs in batches too. Too much work to make just one. My friend here in the states has a small box of Alfis semi finished Purdey springs. I currently have a Lancaster body action with a broken mainspring. It's an extremely complicated devil with much milling involved. You could make it solely with hand tools, but it would be silly to. I would venture to say that the Lancaster mainspring might be just a hair more complicated than the Purdey.

Mike Rowe,

That is outstanding work. Thank you also for showing the thickness section of the Dickson spring, interesting to see that it is a little thicker in the middle than either end.

The original broke or did it tire out?

Thanks for the pictures Mike, and for walking it through to the fitting.

That's how I supposed the original Purdey spring would be made, from smaller stock with more bending and forging. I would not be surprised if that raw "V" starts off so big so it can be held for machining. It would be interesting to see how close it is to final dimensions after machining.

Thank you for the kind comments, gentlemen. And Dig, I hope I'm not hijacking your thread here - just trying to show everyone how things get done at bench level.

Both springs needed to be replaced on this trigger plate. The right hand one was a roughly made replacement, and the left one was the very early style held to the tumbler by a tiny screw. The ears had broken on the tumbler and spring, so the decision was made to modify it to the later style with the seat and roller (the right side was already modified). "Later" is a comparative term, judging by the early round actions I've worked on it would be sometime in 1884, still quite early in the scheme of things.

Just my take on the picture of the spring blank, but I'd say it was probably made from cutting a straight bar of about 3/8" rolled steel with grain direction lengthwise, then hot forged for the bend to give it the proper grain direction around the bend. I doubt the Purdey engineers missed anything. No castings here.

Chuck

I want to agree with you, forging is the start for a spring, so I was taught. But look at the inside of that V shaped piece. That surface looks mightily like the one my EDM collaborator gets. Forged surfaces tend to be a lot rougher than that.

Now it could be that the EDM process is used to clean up the forging, which would be a clever use of the technology. But if the end result is a durable spring, the how becomes a bit secondary.

I think you folks would know better. Looks to me like 3/4" or maybe 1" stock that has a saw slit down the middle. Then forged to open up the "V". It doesn't look like the "V" itself was forged 180* back on itself.

The inside of the "V" doesn't really look cleaned up too much. Maybe surface ground to true up the top and bottom. There does seem like some nasty inclusion down where it's being held. I'd bet as they were slabbing off springs, they might not want to use that area. Surprised it doesn't make the whole piece suspect, because not much is invested up to that point.

I think it's so bulky just to make sure the pattern of a spring fits in there without too much worry. Maybe, but that rough stock doesn't look like much advantage would be gained up to that point with EDM.

I just have hard time believing that a Purdey engineer would not get the grain right. The forming to that shape could easily done when hot and the first outward bends of the ears done in a pressbrake, the center bend started in the pressbrake, then closed by pinching the outside in the pressbrake. All done while hot, probably in less than a minute. I just don't see any reason to use machining or wire EDM to make that raw part. If they sawed it or used wire EDM, they sure lost me on the logic. But there's always a bunch of ways to make something.

Only interesting conversation Chuck, no big deal stuff. If that 180* were forged. I thought I'd see much more distortion like compression on the inside and stretching on the outside of the bend. It might be very difficult to maintain the same thickness of material around that bend.

Maybe, the loss of grain flow around the 180* could be made up for by using a known alloy steel and modern heat treat practices. Agreed, traditionally I'd think bends, curves and likely tapers were all rough forged to get it close and probably more sound. I think a couple more pictures downstream in the process would be interesting to see.

For the 180 bend area of the finished spring, if you knew it wasn't ideal grain direction, you'd simply make it thicker there so it doesn't flex in the 180. All the spring response is in the arm of the leaf anyway.