EDM Chambering

[TRA]

Something that is being stated here, is that stress warps metal, well not always. A machined part can stay dimensionally stable and still be full of stress.

Don't think for a minute that if it didn't warp, that you put no stress in it. The proof in the pudding is the useful life of the part.

Anyone have any references to the statement that machining removes stress?

If saying that machining removes stress, then why not just use stress relieved material, to begin with? And why does it then need stress relieved after you cut on it?

It's because machining induces stress, period.

Chad
Your experiences with engines, while a good story, is more to do with the fact that cast iron is not a stable material and moves around, more so while it's green. Those practices are not necessary in todays world of high performance....We used to say the best drag racing block was one with 100000 miles on it and had a solid coating of rust. Yet the factory teams used new iron, go figure.

 

[4Mesh]

* OK we're past the end mill idea. Ever run a planer or a shaper?

No I have not, but I do have one. I've honestly never seen it powered up. It's an old Cincinnati and honestly, I don't know what I'd use it for. I don't think it's got enough stroke for gib work like what you're talking about, but I don't know.

Interesting stuff all the same. While some folks don't like breaking things down quite so far, I sorta enjoy the discussions.

 

[Charles E]

Anyone have any references to the statement that machining removes stress?

Yes, Dan Lilja. Quite some time ago I phoned him about fluting barrels, and whether or not that induced stress. "It relieves it" he said. When I probed, he explained that what he meant was the fluting more evenly distributes what stress is already there.

Well, he's an engineer and I'm not. You asked it anyone had a source . . .

 

[TRA]

http://www.riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htm

For those that want to read Lilja's opinion which also mirror Chads , use this link and scroll down , you will find it.

http://www.riflebarrels.com/faq_lilja_rifle_barrels.htm#stress

Engineers do disagree and I have furnished, what should show, that not everyone agrees with what is said about "stress". Sometimes old beliefs are hard to change.

 

[squeakie]

No I have not, but I do have one. I've honestly never seen it powered up. It's an old Cincinnati and honestly, I don't know what I'd use it for. I don't think it's got enough stroke for gib work like what you're talking about, but I don't know.

Interesting stuff all the same. While some folks don't like breaking things down quite so far, I sorta enjoy the discussions.

I once worked with an old Sweed that used to run a planer. He'd set a block of steel up so that the table would knock it onto the floor, and then waking him up! You can do some nice work with a shaper once you get the hang of it. I knew a guy that made triggers on a shaper. Now we'd just wire them out!
gary

 

[squeakie]

Yes, Dan Lilja. Quite some time ago I phoned him about fluting barrels, and whether or not that induced stress. "It relieves it" he said. When I probed, he explained that what he meant was the fluting more evenly distributes what stress is already there.

Well, he's an engineer and I'm not. You asked it anyone had a source . . .

I'm not familure with Dan's process for building a barrel, but before he starts the gun drilling operation, I'd have to assume he normalizes the barrel stock. Then straitens it if it's needed. When he drills the barrel he either adding or relieving stresses in the I.D. of the barrel (depends on which camp your out of). But If the barrel blank was normalized from the start, I'm putting my money on the cutter induced stress. If the blank is left untouched then I'm the otherway. I do know for a fact that cutting tools that turn induce certain amounts of stress because I've had to deal with it the past (even after a couple of normalizing operations). Yet I also never saw this in a plaining operation, and will have to assume the old men I learned from were right.. I've also cut a lot of very tight parts on a wire, and saw little if any changes in the parts (cut lots of gear profiles that were held under a half thousandth on profile and spacing). Sometimes the blanks were already hardened and sometimes they were not.
The reason I made reference to a machine gib in my other post is that of all the things I've made or remachined in the past I found that these tend to warp the easiest. And more than once I've had one destroyed just by running an 1/8th" ball mill cutting oil grooves. I've found that some steels that are cold rolled will take a twist while being machined, and I think Chad is right about this in relieving stress. I'm gonna run this by my brother inlaw this week, as he has a much better understanding of the stuff than I do.
gary

 

[RoyB]

Great thread!

A few comments.......The wood warps simply because of different moisture contents from a side that had previously started to dry and the inner wood that is holding much more moisture. If you are going to rip saw construction grade wood, which is not straight grain and has way more than 10-15% moisture content, it WILL warp. You can stack it and band it and try all kinds of things, but it's gonna warp.

Bruce Baer was cutting a wildcat based on the 30-378 Weatherby. A really big cartridge. I've read of others that were CNC turning chambers with spectacular results. I can't see why it wouldn't be a good method. And of course some European rifle makers are hammer forging the whole Chamber. I've seen some of Sorois' EDMed barrels from up in NH. The chambers are beautiful and they shoot great. I haven't heard from him in a year or so and his website is closed. Hope he is OK.

I don't want to start another war, but when I read about 300 Below and low temperature stress releaving, I hear about ausinite (sp?) and some other kind of "nite" and getting all the 'nites" to line up and it makes better steel etc, etc, etc....Sounds like a good idea to me.............comments?

 

[Bnhpr]

Ok, traditional machining induces stress and removes stress, everyone knows that anyway?

A couple of questions:

On fluting...How much does the barrel move from fluting (416), in the real world. has anyone measured before and after?

Has anyone tried EDM fluting?

 

[4Mesh]

A couple of questions:

On fluting...How much does the barrel move from fluting (416), in the real world. has anyone measured before and after?

I've fluted 416 barrels of 30" length with 12 rather deep flutes and never seen even a bit of warpage. These were done with coolant, climbing with a saw cutter, in a cnc. Flute lentgths were in the neighborhood of 20" long and 3/16" wide. depth varied from one end to the other in order to make it look pretty, I did 12 flutes vs the normal 6 and could not get that many around the barrel at the minor diameter full depth, thus the taper. This barrel when rolled on a surface plate was as straight as could be, and I'd done a 2 operation (turn it around) tapering on it before doing all this. (actually, did on every one I ever made). Tapered in an Okuma lathe (with coolant) with only 15" between centers so I had to turn it around. So, if I put stress in when tapering, then I must have removed some when fluting. Damned if I know why it stayed straight but it did. At least one of these when finished was top level competitive. But, there's other ways to skin that cat so I don't bother with it any more.

 

[4Mesh]

Has anyone tried EDM fluting?

I'm not sure how this would be done. You'd have to flute all the way to the end of the barrel if you wired it, and it would take a hell of a big edm. Read- $$$$$ Cha ching...