# Homemade Edm To Remove Broken Taps



## Billh50 (Nov 22, 2015)

I found a page with some basic plans for an EDM to remove taps. And since we all break taps now and then, I thought I would post a link.

http://pico-systems.com/edm.html


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## kvt (Nov 22, 2015)

Thanks for the link


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## Morgan RedHawk (Nov 22, 2015)

I have been thinking of building and EDM, too.  This guy has books and PCBs for 2 types.  I am thinking about ordering the book for the pulsed version.

http://www.homebuiltedmmachines.com/

I am wondering, how do you shape the electrodes for custom shapes?  
Any input from anyone that has built or used an EDM would be appreciated.


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## Billh50 (Nov 22, 2015)

The shaped electrodes are usually  made from a carbon rod. They are machined for the shape needed.


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## uncle harry (Nov 22, 2015)

Billh50 said:


> The shaped electrodes are usually  made from a carbon rod. They are machined for the shape needed.



Copper has also been an electrode material. I've had hardened S7 alloy edm shaped to de-gate dozens of very small plastic parts for pick and place decades ago. Since graphite is the electrode of choice some shops have specifically isolated rooms with lathes, mills and other tooling to isolate the mess from other areas.


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## Billh50 (Nov 22, 2015)

Well every place I have worked that had an EDM used the graphite or carbon rods for shapes. They also used the copper for burning thru taps and broken dowel pins.


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## Smithdoor (Nov 22, 2015)

looks great

Thank you
Dave


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## ch2co (Nov 22, 2015)

Add anther small project to my to do list.  Looks like fun to try out. I've seen commercial EDM's working, but never thought that
it would be so simple for a hobby shop.  Thanks!

CHuck the grumpy old guy


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## bpratl (Nov 23, 2015)

Just added this project to my very long DIY list. There has been many a time that I could have put this to use.
Thanks again for sharing. Bob


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## Billh50 (Nov 23, 2015)

I was thinking about the one I posted. If some electrode holders were made to take different diameter copper tubing. Then a holder for them to be mounted into with a fitting and hole to allow fluid to flow thru tube. That would keep the grit out of the hole that is being burnt. This would work just like conventional machines.


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## RJSakowski (Nov 23, 2015)

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


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## John Hasler (Nov 23, 2015)

RJSakowski said:


> 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.


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## 4GSR (Nov 24, 2015)

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


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## Billh50 (Dec 20, 2016)

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.


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## Mark_f (Mar 11, 2017)

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.


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## whitmore (Mar 13, 2017)

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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