Homemade Edm To Remove Broken Taps

How about using hypodermic tubing for the electrode? 18 ga. (.050) tubing has a resistance of less than 1 ohm/ft. McMaster Carr sells it as precision miniature stainless steel tubing from .008" to .253" O.D.

Bob
 
How about using hypodermic tubing for the electrode? 18 ga. (.050) tubing has a resistance of less than 1 ohm/ft. McMaster Carr sells it as precision miniature stainless steel tubing from .008" to .253" O.D.

Bob
It isn't just about the resistance. The electrochemistry matters as does thermal conductivity.
 
The old tap burner dad and I used to, toohave, an old Elox brand, we used plain water for the coolant and wen to the local hobby shop and bought brass tubes from 1/16" all the way up to 5/8" in size. We had all sorts of fittings for adapting the tubes to, an some of them we soldered them to the fitting. We redesigned the tap burner a little from original, replaced the collet system they had to a 3/8" NPT thread to simply things.

With the welders of today available to us, I would not hesitate taking one with spark gap control and adapting it to a tap burner. The vibrating head used on one can easily be made from a solenoid used to open a valve stem. just put a limit switch on the end to break the circuit momentary, letting the solenoid go back up, hitting the limit switch again. There are other ways of creating the "vibrating" thing needed to control contact of the electrode with the work.

Ken
 
I do remember buying small copper tubing from hobby shops years ago. We would cut and solder the tubing to make a chassis for slot cars. They had several small sizes.
 
Some of you may have seen it , but I am building Ben Fleming's Pulse EDM machine on here now. It is not a cheap thing to get into, but can be very useful. You can build a simple tap burner very cheaply, but as many of you know ( when I build things), I got carried away and am building a much more versatile machine to do a lot more than tap burning. I used EDM in the machine shop many years ago ( when vacuum tubes were the rage) and they can do a lot of machining operations you cannot do on the mill or lathe. If interested, check it out in Members Projects.
 
I've used tungsten rod, for EDM'ing narrow holes (0.040"), in boron carbide. By tungsten,
I mean the soft tungsten metal, available as wire, not tungsten carbide. Kerosene bath
with a pump to flush the cut (Shell Diala AX specifically, but it sure looked like kerosene).
We used an aircraft 28V oil pump, but I see lots of 12v diesel/fuel pumps for automotive
use that would probably circulate fluid just fine.

I recall some cuts worked best with the wire probing UP into the work.

What I do NOT recall, is if the whole apparatus cranked up from the coolant tank, or whether
the tank dropped down to set up the tooling and workpiece.
 
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