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Barrel bores and electrical discharge machnes?
- Thread starter DonC
- Start date
Funny you bring this up, Im having a tough time on a edm right now controlling runout going 10” deep, couldnt imagine trying to do 30”! But, im at max capacity so maybe on a bigger machine. Wouldnt be my first choice though.
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I was thinking a EDM could be used and calibrated to perform the same function as a Reamer, only with more precision. Perhaps it could also make continuous taper barrels.
I didn't think it could be used to drill the bore from solid stock, just as a Reamer technique.
I didn't think it could be used to drill the bore from solid stock, just as a Reamer technique.
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When a machinist apprentice near 40years ago and EDM was in its infancy, while crazy tight tolerance was possible, surface finish relative to what we see in gun barrels surface finish & smoothness was not even close !!!
Electronic arc between an electrode and the barrel being the anode leaves a microscopic crater type finish as the process happens from what my memory remembers seeing electron microscope pics of an EDM eroded surface on 17-4 stainless , Nirtonic-50 stainless & 304L stainless and similar high strength steels.
Times may have change in the tech ? ... just sharing past experience FWIW
Electronic arc between an electrode and the barrel being the anode leaves a microscopic crater type finish as the process happens from what my memory remembers seeing electron microscope pics of an EDM eroded surface on 17-4 stainless , Nirtonic-50 stainless & 304L stainless and similar high strength steels.
Times may have change in the tech ? ... just sharing past experience FWIW
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There was a company in the 90s in Tx that did a process they called "Blackstar", I think. They were doing electro-polishing on medical equipment and branched out to include precision barrel polishing. Claimed they could take a GOOD barrel and polish out all the minute imperfections to create a bore with less than .0001" variation over the length and very high surface finish. They also said they could taper polish up to .001" over the length. Wasn't cheap but I regret not having one done, to at least see. I only know of one person who took advantage of that and he claimed some pretty incredible results but I guess the demand or results weren't enough as it seemed to go away in a couple of years.
Interesting idea, regardless .
Bob
Interesting idea, regardless .
Bob
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EDM and a SMOOTH surface doesn't go together. An EDM electrode providing a 16 or even a 32 RMS finish...I don't think that's possible.
Plus there is a "recast" layer left over that is very hard and brittle. Some newer machine have "somewhat" gotten around that and are leaving a thinner softer recast layer, but it's still there, and it's still not smooth enough to be considered a fine enough finish for a barrel bore.
Plus the way that EDM works (plunge style), I'd have a hard time believing that a barrel much longer than a short pistol barrel could be machined accurately.
Mike
Plus there is a "recast" layer left over that is very hard and brittle. Some newer machine have "somewhat" gotten around that and are leaving a thinner softer recast layer, but it's still there, and it's still not smooth enough to be considered a fine enough finish for a barrel bore.
Plus the way that EDM works (plunge style), I'd have a hard time believing that a barrel much longer than a short pistol barrel could be machined accurately.
Mike
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Weve gotten an 8 finish, according to a profilometer that I trust, but like motorhead said its not a finish Id want in a barrel. It does polish up by hand very quickly though.
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I first thought of a ram edm using a broach like electrode design but the problem with ram s is that not only is the barrel reduced of metal the electrode wears as well. That leaves me to think taper. Not a good thing I think?
I did work with a kid that had an amazing mind when being able to twist a wire edm wire into some pretty exotic shapes which would create one thing on one side of the steel and something completely different on side 2 at 180 degrees. One of his simple ones I was lucky to get was...
Side 1 .USA Side 2 #-1
Of course this was on a block of 1-1/2" thick steel. A 30" barrel may pose another challenge given the shallow groove depths. And then there is always figuring out how to polish the rough burn surfaces without drilling the edges of the lands.
Nope, I just talked myself right into using a broach again
I did work with a kid that had an amazing mind when being able to twist a wire edm wire into some pretty exotic shapes which would create one thing on one side of the steel and something completely different on side 2 at 180 degrees. One of his simple ones I was lucky to get was...
Side 1 .USA Side 2 #-1
Of course this was on a block of 1-1/2" thick steel. A 30" barrel may pose another challenge given the shallow groove depths. And then there is always figuring out how to polish the rough burn surfaces without drilling the edges of the lands.
Nope, I just talked myself right into using a broach again
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