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very cool project brino. Would the tungsten for tig welding work as an electrode?
Greg
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Electrical Discharge Machine Version 2 (edmv2)
- Thread starter brino
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- Jan 2, 2014
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You know what? I thought of that one night in passing, but did not write it down.
I'll add it to the list.
Thanks Greg!
-brino
- Joined
- Jan 2, 2014
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Hi All,
I got some time to try some other electrode types.
Theory says to use graphite electrodes. Not having any of those on hand, and continuing in the experimental ways of this project I tried carbon-cored, copper-clad electrodes. I have these on hand as my first welder was a home-made unit using an old electric space heater I got at a yard sale. That unit was based on one my Dad made, and I believe his was roughly modeled after an old popular mechanics article where they removed the carbon rods from alkaline D-cells. My 120V welder basically has a high-current heater element in series with an insulating handle that allows you to bring two of these electrodes together (the heater element would glow) then separate them and a beautiful purple arc would form between them. It was mostly used to braze, but could get hot enough to weld thin steel parts.
Here's the package from the last set of these electrodes I bought along with some random electrodes:
Here are four holes and the electrode used:
It took only 6 minutes to puncture the utility knife blade.
It took about 8 minutes to produce a clean thru-hole............This surprised me!
The previous tests with hollow copper and brass tube electrodes removed (burned, disintegrated, eroded?) only a thin ring of material.
This solid electrode had to "process" a much larger volume of material so I expected it to take longer.
Maybe that's why it is preferred.
Full sized pictures below.
-brino
I got some time to try some other electrode types.
Theory says to use graphite electrodes. Not having any of those on hand, and continuing in the experimental ways of this project I tried carbon-cored, copper-clad electrodes. I have these on hand as my first welder was a home-made unit using an old electric space heater I got at a yard sale. That unit was based on one my Dad made, and I believe his was roughly modeled after an old popular mechanics article where they removed the carbon rods from alkaline D-cells. My 120V welder basically has a high-current heater element in series with an insulating handle that allows you to bring two of these electrodes together (the heater element would glow) then separate them and a beautiful purple arc would form between them. It was mostly used to braze, but could get hot enough to weld thin steel parts.
Here's the package from the last set of these electrodes I bought along with some random electrodes:
Here are four holes and the electrode used:
It took only 6 minutes to puncture the utility knife blade.
It took about 8 minutes to produce a clean thru-hole............This surprised me!
The previous tests with hollow copper and brass tube electrodes removed (burned, disintegrated, eroded?) only a thin ring of material.
This solid electrode had to "process" a much larger volume of material so I expected it to take longer.
Maybe that's why it is preferred.
Full sized pictures below.
-brino
- Joined
- Jan 2, 2014
- Messages
- 9,606
....also, as Greg (@f350ca) suggested I tried a tungsten TIG electrode.
It made a clean hole thru the utility knife blade in 6 minutes (see the orange circle):
I need to measure the consumption rate of the electrodes to make this a more scientific dissertation, but I want to keep this fun, not work.....
Once again full sized images are below.
Be well!
-brino
It made a clean hole thru the utility knife blade in 6 minutes (see the orange circle):
I need to measure the consumption rate of the electrodes to make this a more scientific dissertation, but I want to keep this fun, not work.....
Once again full sized images are below.
Be well!
-brino
- Joined
- Jan 2, 2014
- Messages
- 9,606
It has been a while since my last update, but recently I had to fire the machine up for more than just testing.
I snapped off a 6-32 tap in a workpiece!
The project is a custom drill extension for a friend. He's making wooden salt shakers and pepper mills. For deep drilling of the bodies he needs to run his current forstner bits deeper than the shanks allow. Some off the shelf drill bit extenders are available, but all the ones we saw had heads bigger than the 1" minimum size hole he wanted.
I came up with this:
The idea behind the double-ended split clamp is to allow use of various shank lengths, or even to allow stepping the length up but retain minimum tool stick out at each step.
It's a 4-1/2" long piece of 7/8" dia. steel bar drill 2" deep at each end for a 3/8" shank. (The hole does not go thru.) The side is slit along the entire length, but I still need to slit half way thru the bar 1-1/2" from each end to provide a split clamp. I was going to do the last slits after tapping the holes for four 6-32 socket-head cap screws.
Of course I broke a tap.......Bugger!
the tap:
the plugged hole:
My EDM machine is not exactly finished.....I still need to incorporate an arduino power supply and a stepper motor power supply (still using a bench supply for both), I want to try different spark power supplies, I need to package it all up, I'd like to make a more adjustable head, etc.
I tried to just pick and punch the broken tap tip out, but it would have none of it......so EDM it is.
I used a piece of 14AWG house wire as the electrode and lined it up in the plugged hole:
After only a few minutes I could tell by the rhythm of the machine that it was thru!
Then just a small punch got out the rest of the debris from the broken tap. I followed that with the tap drill to be sure it was all out.
It worked!
I had to buy a new tap and have not had a chance to try again. Hopefully the hole wall is still "soft" and normal.
I'll try to post back with a video of it working too.
-brino
I snapped off a 6-32 tap in a workpiece!
The project is a custom drill extension for a friend. He's making wooden salt shakers and pepper mills. For deep drilling of the bodies he needs to run his current forstner bits deeper than the shanks allow. Some off the shelf drill bit extenders are available, but all the ones we saw had heads bigger than the 1" minimum size hole he wanted.
I came up with this:
The idea behind the double-ended split clamp is to allow use of various shank lengths, or even to allow stepping the length up but retain minimum tool stick out at each step.
It's a 4-1/2" long piece of 7/8" dia. steel bar drill 2" deep at each end for a 3/8" shank. (The hole does not go thru.) The side is slit along the entire length, but I still need to slit half way thru the bar 1-1/2" from each end to provide a split clamp. I was going to do the last slits after tapping the holes for four 6-32 socket-head cap screws.
Of course I broke a tap.......Bugger!
the tap:
the plugged hole:
My EDM machine is not exactly finished.....I still need to incorporate an arduino power supply and a stepper motor power supply (still using a bench supply for both), I want to try different spark power supplies, I need to package it all up, I'd like to make a more adjustable head, etc.
I tried to just pick and punch the broken tap tip out, but it would have none of it......so EDM it is.
I used a piece of 14AWG house wire as the electrode and lined it up in the plugged hole:
After only a few minutes I could tell by the rhythm of the machine that it was thru!
Then just a small punch got out the rest of the debris from the broken tap. I followed that with the tap drill to be sure it was all out.
It worked!
I had to buy a new tap and have not had a chance to try again. Hopefully the hole wall is still "soft" and normal.
I'll try to post back with a video of it working too.
-brino
Last edited:
- Joined
- Jan 2, 2014
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Ha, nope! I would never break a tool intentionally.
....but I have had enough accidents that I knew an EDM would be worth it!
-brino
Last edited:
- Joined
- Nov 8, 2013
- Messages
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Back in the day, our automobile oriented machine shop used hex shaped carbon rods, submerged in a jury rigged puddle of kerosene to erode hex shaped holes through whatever was broken off inside some threaded holes of very expensive parts. Once the hex hole was developed, an Allen wrench would unwind the stub. Problem was, someone "borrowed" our EDM for an emergency job, and that was the last we saw of that beloved EDM.
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