# Spark erosion tap extractor



## mgbrv8 (Jan 24, 2012)

Does anyone know where I can find some simple plans for simple tap spark erosion machine??

Dave


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## lazylathe (Jan 24, 2012)

Hi Dave,

This is the one i know about.
Although i am sure there are some others out there too!

http://www.metalwebnews.com/manuals/spark-erosion.pdf

Andrew


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## doc1955 (Jan 24, 2012)

Seems to me I recall a build in the Home Shop Machinist mag back awhile I can dig them out and look for it if you are interested in getting the back issues. I'm pretty sure the back issues are available.


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## Blogwitch (Jan 25, 2012)

I have put a plan in the download section

http://www.homemodelenginemachinist.com/index.php?action=tpmod;dl=item381


John


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## Blogwitch (Jan 25, 2012)

I forgot to mention, with all spark eroders (as far as I know), the piece part and the lower profiled arcing piece should be immersed under a dialectric solution.

I have yet to build this, but normally, for something this size, and I will be doing it this way, you could just stand it in a small tray containing paraffin (kerosene) so that the liquid covers the job.

Do keep an extinguisher handy, just in case of accidents.


John


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## Ken I (Jan 25, 2012)

Nice one Boggs. I've always wanted one of those. Worth a KP.

P.S. I have seen 2 industrial sparkers damaged badly enough to be insurance write off's due to fires - in both cases left unattended at night - in both cases they were lucky not to lose the entire factory.

In both cases the dialectric ran low - to below the sparking - due to pump / flow problems.

Extinguisher and an eye on it mandated.

Ken


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## arnoldb (Jan 25, 2012)

Thanks John Thm:

 : Another tool to build... This one will come in very handy though; I have several projects in the pipeline where it will be useful.

Kind regards, Arnold
Edited to take my feet out of my mouth


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## Arnak (Jan 25, 2012)

Hi Dave,

This is what you need:-

http://tech.groups.yahoo.com/group/EDMHomeBuilders/

Brilliant group, can supply the PCB and instructions to build the unit with lots of help and advice.

There is even a new pulse type eroder being planned.

Arnak


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## joeby (Jan 25, 2012)

Fires are a definite hazard with an EDM machine, sinkers in particular. Wire EDM's and most "holepoppers" that I have seen use de-ionized water as the dielectric. Kerosene was used in commercial sinkers at some point in time, as I understand, but I have never actually seen it used. All the commercial machines I have run over the last 25 or so years have used commercial dielectric fluid.

 Dielectric fluid has many advantages over kerosene, except for the price, $8-900/55 gallons last I heard. This makes kerosene the more likely candidate for use in the home built machines. One EDM supplier was selling dielectric in 5 gallon pails at one time.

 Anyway, commercial machines have a simple float located inside the tank that stops the machine in the event that the dielectric level drops. A float switch would be a worthwhile addition to any of these shop built machines, in my opinion. It would cut the power to the machine faster than you could react to a sudden dielectric loss, and hopefully before the work is uncovered. Kerosene, once ignited, would continue to burn even after the power had been cut off, I would think. I have seen a few fires on commercial EDM's, and most were extinguished as soon as the power was cut, one had enough of a head start to continue to burn long enough to cause serious damage, and these were using dielectric fluid. All but one of these fires, as I remember, were a result of that float switch being tampered with, (disabled) or purposely burning above the fluid level, the other was actually caused by a dc arc. A dc arc causes material to be deposited on the workpiece causing the machine to back away, this buildup can continue to the point that the spark gap is above the fluid level.

 Kevin


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## Ken I (Jan 25, 2012)

arnoldb  said:
			
		

> Just a little heads-up on the circuit drawing...
> 
> I went through it, and the 600V 5A suppression diode shown between the "chuck" and the "workpiece" is shown the wrong way around in the circuit drawing.



Arnold - I think its the right way - ground is positive the electrode is negative.

Ken


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## Blogwitch (Jan 25, 2012)

Arnak,

The reason I put these plans up was to get away from the very fancy and grossly over technical designs that are out there. Which it seems that link you have put up there points them to, most probably boffins with formulae and circuits spouting out of every orifice.

All that is needed here is something to dig out a broken tap or make a square hole, not dig another channel tunnel or erode around corners.

Kevin,

The reason I quoted kerosene was purely for the reasons you stated.
I worked in a model shop, and our small spark eroder (mainly used for removing broken taps etc) did use kerosene, and was plenty efficient enough without going to any extra expense.

As I said above, I showed it because I didn't want to baffle people with the bullsh that normally comes out of the woodwork on posts like this, and makes things too difficult for the average layman to get his head around.

KISS

John


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## arnoldb (Jan 25, 2012)

:-[ Thanks Ken, you're right. I edited my previous post.

A little embarrassment will teach me to look at the circuit drawing a bit more carefully... Got caught out by the tradition of keeping the positive side of a circuit drawing at the top.

If you hadn't mentioned it, I would have built the darn thing with everything to the wrong polarity :big: - so thanks for the heads-up Thm:

Kind regards, Arnold


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## joeby (Jan 25, 2012)

John,

 I understand your reasoning, and have no issues with the design you posted. 

 I have seen many individuals buy an industrial EDM without realizing the expense associated with maintaining and operating it.

 My day to day job is EDM, and do not, would not, have one in my home shop because I can't justify the cost. As a result, I too have an interest in the small, home built machines. 

 My reason for posting was to point out that a lawnmower float, and a micro-switch might be a worthwhile addition.

 Kevin


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## Ken I (Jan 26, 2012)

arnoldb  said:
			
		

> Got caught out by the tradition of keeping the positive side of a circuit drawing at the top.


Arnold, that's alright - I made the same mistake on the first read through.

Ken


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## joeby (Jan 26, 2012)

I'm not familiar with the burning characteristics of the home-built generators, but I think copper would still be the best bet for electrode material. Copper tube does a good job, especially if you can flush down through the tube. The tube will leave a post, of course, in the center of the tap, which causes erratic burning due to shorting. I like to stop just short of breaking through the tap and break out the post with a punch or by just grabbing it with needlenose pliers. The tip of the tap usually comes out with the post and the flutes will fall into the hole.

 One place I've dealt with on several occasions is Saturn EDM. They never had a problem with small orders, and were always easy to work with.http://www.saturnedm.com/index.html

Kevin


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## Blogwitch (Jan 26, 2012)

Kevin,

Nice link, a good source of consumables.

I do have a nice bundle of those copper electrodes with holes down them, but also a load of tungsten tubes as well, they are what we used for small tap removal, but you can just make copper electrodes from the solid. If you want to erode a square hole thru say some sheet or even a block, just machine up a square copper electrode. A syringe helps if you can't get fluid flow, just retract the electrode (shut off first) every so often, and squirt some fluid down the hole, just to clear out some of the loose debris.

I suppose with that easy planset, you could in fact mount up some sort of micrometer head stop as well. That would then give you very accurate hole depths.

But as I have said, don't go too far, and keep it as simple as possible, just enough to get the job done, and with a tiny bit of modification, do maybe a couple of other auxiliary jobs as well.

The reason I haven't bothered to make one of these units is that a friend can get eroding done for me overnight, I call him up, he picks it up at about 8pm, I go to bed, when I get up in the morning, he drops it off between 7 and 8am. 
Unfortunately, he retires soon, so now my interest in getting one made. I might only use it once a year, but for the cost and effort involved, it could save me weeks of work if problems occur at the end of a piece part manufacture. My main problem isn't usually tap breakage, I seem to have that well under control, but I occasionally do break off tiny drills down blind holes. Rather than risk damaging the job trying to get it out, once it is eroded, it is though nothing was ever wrong, and I can continue from whence I came.

John


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## Herbiev (Jan 26, 2012)

Thanks Bogs. A karma point from me too. I could probably build one of these EDMs in the time it takes me to remove a broken tap. I just HATE that job


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## joeby (Jan 26, 2012)

A suggestion for workholding, one of the cheap mini-mag type indicator holders (or similar) flipped upside down and bolted to the machine base would make a nice mag chuck for this size EDM.

 Kevin


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## deverett (Feb 2, 2012)

There are a couple of videos on YouTube showing a simple home made spark eroder being demonstrated at Cabin Fever. Unfortunately, I have changed the link name and can't find them now!

Dave
The Emerald Isle


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## ref1ection (Feb 2, 2012)

I believe this is the link you're looking for.
[ame]http://www.youtube.com/watch?v=d9w-P8QAseg&feature=related[/ame]

Ray


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## lee9966 (Feb 26, 2012)

Nice video, thank you for posting that.

I built a simple EDM like that using a solenoid from an automobile starter, the kind with a separate solenoid not right on the starter. It works, at least to the point where it makes consistent sparks, but I need to set up a pump system apparently. Right now it just makes big jagged holes, not accurate enough for any real purpose.

I thought my problem was that the guide for the movable part allows too much slop, but in that video the tubing is just some plastic pipe and doesn't seem to rely on an accurate guide. I think I need to revisit my hacked together ugly attempt after seeing such a simple design work.

Mine uses a couple of those tubular halogen light bulbs as a giant resistor in case the tip welds to the material being cut. I am using a big transformer, giant capacitors and a rectifier. A car battery would be simpler and better. I wonder if SWMBO would notice a battery missing from her car?

Lee


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