EDM work

S

Steelgaze

Joined
Jan 21, 2003
Messages
53
I was wondering if any of the makers on these forums have or do work with EDM (electrical discharge machining) on there knives? I have a project coming up in my tech school course and was contemplating making a knife... unfortunately I don't have a decent setup for grinding blades available so I was thinking about ram edm'ing the "grinds" on the blade. I also figured that if I was going to ram edm the grinds that I might as well harden/temper first and use the wire edm to cut out the blank shape... just wondering if anyone has any comments/questions on this

also, any suggestions for a good steel to try for my first knife? I was looking at a knife supply store that would heat treat blades and was thinking that it would take a lot of the problems away from me if I didn't have to try and do the heat treating in our less than good setup at school.

thanks for any info

Chuck
 
If you EDM after hardening you MUST temper after EDM. With EDM there is a thin layer of martensite formed because EDM actually vaporizes the steel.This then is untempered martensite and must be tempered. EDM before hardening might also cause problems so tempering there would be a good idea too .....A good beginers steel is 5160.
 
There have been problems with EDM and stainless, air-hardening and easily work-hardened steels, so play it safe and go with 1095 or 5160.

Last time I priced EDM it was at least 3 times as expensive as laser-cutting (10+ quantity) and almost twice as much as water-jet cutting, so I gave up on it. Maybe it was just this particular shop, but it didn't seem worth the cleanup effort.

Probably better off bribing someone here to profile something for you to help you get started...
 
Are you guys familiar with Eastern Mountain Sports? Heck, anyone from the Northest definitely is. Anyway, back in the 80's EMS had Spyderco make them their own special skeletonized knife. The blade was EDM'ed-out and there was the EMS logo, a mountain, etc in the blade. It was a really lightweight backpacker's knife. Trouble was that the blade was very weak and was discontinued.

Just figured I woudl toss that in there for you Chuck. Perhaps a little research by calling Spyderco???:p
 
since I got a quick response on that question, I'll throw another one out here. has anyone tried to work talonite on an EDM? I read that it edm's great, but what are the side effects metallurgically? I'm planning on edm'ing the knife I make one way or another, I'm just trying to gather as much info as I can. Thanks again.

Chuck
 
That's an interesting forum....While EDM with steel presents a problem of untempered martensite which leads to cracking Talonite does not have martensite. It's hardening mechanism is age hardening and you would then form a thin layer of softened material.... The EDM process actually vaporizes the surface of the material (that's VERY high temperatures)....You might contact the manufacturer of Talonite to get specific recommendations.
 
Guys, the recast layer on an edm'd part is only about .0005" max on a rough pass, and then only about .000050" thick when multiple finish passes are made. A pass through the glass bead cabinet should about sum that up. If the heat treated piece is tempered and stress relieved correctly after heat treat, there should be no problem.
 
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