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Online Catalogue last updated 24th of December 2015

The EDM How-To Book by Ben Fleming

cover photo

Electrical Discharge Machining. Although this magical metal working system has been around for decades, you won't find it in but a few home shops. But you can build one. And you, too, can do magical things!

Here you get a book loaded with detailed how-to, practical tips, and further design ideas. And it's all proven. No pie-in-the-sky. This works.

The system here uses a simple RC (resistor-capacitor) power supply. Pros will tell you that it's not as good as a digital supply because it erodes graphite electrodes rapidly. That's true. But electrodes have been improved so much over the years, that erosion isn't nearly as bad as it once was. The RC system is simple to build and works well.

The few, home built systems around usually use stepper motors to drive the ram into the work. Ben will show you how to use a airplane trim servo (almost $US150) to do the job. But if you're handy with tools, and if you're not why are you reading this catalogue?, he'll show you how to build one for far less money. Ben's servo system is quite simple.

The power supply is made up of three transformers, two large resistors, and easily obtained electronic components soldered to a printed circuit board he got at Radio Shack. And he'll show you step-by-step how to put it together.

A tank of kerosene and electrical sparks sounds dangerous, and it can be. But as long as the sparks occur deep in the kerosene where no oxygen exists, there can be no fire. (I would still have a fire extinguisher handy, no matter what.)

Details of the system are best described by Ben himself in excerpts from the book, and by his illustrations.

"[There are] several moneymaking reasons to build an EDM for small shop use. One is the precision removal of broken taps and drills. It is possible to burn a broken tap, drill, or an easy out from a piece of aluminium without touching the previously formed threads. Other practical applications are, the squaring of corners in milled pockets, or burning odd shaped blind and through holes in pieces.

For example, let's say a seven-sided hole is needed in a piece of hardened steel. Machine a seven-sided electrode and then burn it through the workpiece. With a ram EDM, it is a walk in the park. For the artisan, carve your initials or a design on the end of an electrode (negative or positive) and then burn it into the workpiece. The EDM opens up a completely new world of machining capabilities; your imagination is the only limit, so go for it! This book will show you how you can have EDM capabilities in your shop for a minimal amount of time and dollars invested...."

"Many of you may have attempted to delve into the mysteries of the EDM generator and control circuits... The large EDM manufacturers certainly are not going to tell you anything about generator/control circuit design. I know that from personal experience as one EDM company engineer told me, 'the kind of information you are seeking is proprietary and only actively worked on by about 20 people in the U.S.'

This book is, in part, an attempt to fill the EDM knowledge void. In this book I will give you hands on, step-by-step information needed to build a simple, low cost, automated EDM system."

"Electrical Discharge Machining (EDM) is a process that uses electrical discharges from an electrode to erode an electrically conductive material. As a result, it is possible to erode or 'burn' the shape of the electrode into the workpiece. The following drawing is a of a typical EDM system... comprised of a generator, also known as a power supply, a servo system, a dielectric tank, and filtration system...

The workpiece is placed in the dielectric tank and affixed to a metal plate in the tank. The tank is filled with a hydrocarbon dielectric fluid (such as kerosene), which ionizes in the presence of an electrical field. The dielectric fluid breaks down electrically (i.e. conducts), after a short ionization period, assuming the electrical field intensity is high enough. The electric field is created by applying a voltage between the electrode and the workpiece (known as the gap).

The breakdown of the dielectric fluid is much like the breakdown of air when a large voltage is supplied from the coil in an automotive ignition system to the spark plug. However, since in EDM the gap is typically held to only a few thousands of an inch, the applied voltage does not need to be very large for an EDM 'spark' to occur. Typical operating gap voltages for EDM machines are in the range of 25-5OVDC though the ionization voltage may be quite a bit higher.

The servo system maintains the appropriate separation of the electrode and workpiece as determined by the operator setting the desired gap voltage on the EDM generator... As each spark is discharged from the electrode (the cutting tool) to the workpiece, a small amount of metal is vaporized and a crater is left in the workpiece. The dielectric fluid quickly cools the vaporized metal. The solidified metal particles, known as swarf, are removed from the work area by the circulating of the dielectric oil, and the filtering system traps the metal particles.

The EDM burning process is repeated thousands of times each second. As the workpiece is eroded away by the repeated discharges, the electrode descends under the servo system control. As a result of millions of electrical sparks melting small quantities of metal, it is possible to erode various shapes into any material that will conduct electricity Even some semiconductor materials may be machined via this process. Generally speaking, the hardness of the workpiece has little effect on the burn; this is one of the biggest advantages of the EDM process...."

"I anticipate that there will be more machinists with minimal electronic experience attempting to building the EDM, than there will be electronics persons with minimal machining abilities. Assuming this is most likely the case, I have opted to give a detailed step-by-step description of how to build the control system and generator. If you are a metal working person with minimal electrical/electronic skills you should be able to successfully complete the project if you can follow written instructions closely, perform sound electrical connections on a P.C. board, be able to read and understand simple electrical schematic diagrams, and understand how to use a VOM/multimeter." "To remove broken screws, bolts, studs, etc. in many cases, it is not necessary to burn the complete broken item out. I have, on occasions made a six-sided hex electrode and then burned a hex shape in the broken part. Once deep enough, insert a standard hex key and remove the part...."

"One job I did for a customer that really saved the day for him and put money in my pocket, was burning blind 1/4" keyways in 48 (existing) commercial tool holders with 3/4" bores. The holders were hardened and the blind keyways made conventional machining extremely difficult. I made an electrode of the required size and length. The parts were positioned horizontally and the electrode was extended into the tool holder's bore. Instead of making the cut down to the 6 o'clock position, I chose to move the servo up toward the 12 o'clock position. This made flushing much easier, as the swarf fell out of the cut area. To accomplish this, I rewired the servo to cut going up, instead of down. It is nice to understand the design of the machine so that these kinds of changes are made with ease..."

"A 24 cylinder diesel engine shipboard was down with a broken head bolt. The service person tried to remove the bolt, he ended up with an easy-out broken off, then he attempted to drill it out, yes, a broken drill bit was also in the mix. With a EDM and small servo heads, such as you have built, it is possible to perform the operation in a remote location..."

Below you will find a list of some of the comments have been received on The EDM How-To Book.

Dear Ben
Bought your book on the EDM, must admit it has become an obsession to make it and to see its results.
What drove me to start this was when we had two broken 10mm taps in two cast iron cooler headers.
It took two days for someone to grind them out. This may not happen again but there has been other work in the past where I could have used your machine.
Have got all my parts together apart from the case, and have half built the motor control circuit.
I am a mechanical engineer who has always had an interest in electronics. Never worked with silicon chips in the past, always been with simple circuits with transistors, so I have some knowledge of components.
The reason why i am contacting you is to ask if there has been any amendments to things in your book before I complete this project.
Thanking you for any extra tips you can send me.
(58yo) from Wakefield, England

Hi Ben,
I got your book on Friday and was amazed at the quality of the whole production, including writing, photos, and organization of the material. Well done!! I saw an EDM built from your book at the Cabin Fever Expo in York, PA a few months ago and it was exactly what I was looking for.
I ordered most of the parts online, ---- I'm really excited about getting started. I signed up for the EDM homebuilders discussion group, but haven't been added yet.
Thanks again,
Reid Zeigler

Ben, I received the EDM book this morning. Beautiful work, easy to read and understand. I am going to use a large Leitz toolmakers microscope base for the stand. It has a precise x-y table with no backlash (Including a built-in rotary table) and also has the capability of tilting the column right or left (Burns at an angle!). Thanks for the information and I will recommend your book to others. I'll send a photo or two when I finish the machine.
Thanks again,
Charles Mahlinger

Hi Ben,
I was impressed with the file being etched. I built a home-brew R/C type machine and would not even try something so large.

I would like to thank Ben for showing his EDM at the First CNC Workshop. (Thanks also to Roland for hosting the CNC workshop.)
I have been wanting a small sinker edm for a long time. I have looked at some other designs and felt that they were too complicated for what I wanted. After seeing Ben's machine at the workshop I could hardly wait for the book. I have now purchased the book, and after reading it, would be happy to recommend it to anyone wanting to build a small EDM.
The book is very clear and concise with great instruction and pictures. I am not an electronics guru but I can easily understand how to build this machine. I also want to thank Ben for answering my email questions and for starting this group as a forum for the builders of this machine. It will give us a place to ask and answer questions and share sources of supply. I have already located most of the items and will start assembling next week.
Bill Nelson

Ben -
Just got my copy of the book, and it's fantastic! Though I'd be interested in the possibility of a PC board-----
Anyway, the book is great, and I hope you forge ahead with work on a book detailing a pulse-based system.
- Michael

Hi Ben,
I'd like to introduce myself.
My name is Ken Shinn, and I'm an electronics engineer/hobby machinist. I was curious about EDM and would love to build a machine, and received your book in the mail yesterday. I really enjoyed the layout explaining step-by-step construction; this presentation method turned a book of curious theory into a great hands-dirty practical project document----
-Ken Shinn

Ben, my name is Paul Fournier and I work at Texas Instruments Inc. in Dallas. I just received a copy of your book on the EDM machine. I have read it last night and finished it tonight. I have to say that it is a pleasure to read a technical manual that is written as good or better than I could have written it! Step by step on all parts listed. Thank you and keep up the good work....
I am looking forward to buying more of your books if you do another one. I am going to build this machine very soon-----.
This is just a Thank You note and a pat on the back for doing such a good job!!!
Paul Fournier

I just wanted to say that I found your, "EDM How to Book" not only very well written, but understandable, and well thought out. I've looked over several EDM home shop projects over the last few years.........and I've always passed over them due to the power supply. With our design, and the explanation you've written in your book, I think I might just give this one a try.
Nicely done; Cliff Bates

Hi Ben,
You certainly hit the jackpot with the EDM book - thanks!
May I please order another ----copies to be sent to us via ----- as usual?
If there is any chance you could please do this with great speed, we might just get them before Christmas (with luck).
Adam Harris Camden Miniature Steam Services

Hi Ben,
Bought your book on Ebay about a week ago. First impression: you put _lots_ of work into it. Thanks for putting it all in book form ------
I plan on building one of these to do some specialty EDM sinking on a contract basis for some local clients.
Thank you,
Jason Burton

I'm well started into the process of building a stepper motor EDM. I saw your book on eBay and bought it. I wish I had seen this one before I got so involved learning electronics, circuit board etching and the whole nine yards first-----My second one (if I build a second) will definitely be a DC servo motor. Your's is simple and elegant in design.
William Ager

HI Ben
Your book arrived in Denmark monday the 5. of September.
My first impression off the book is that it contains just what I need to know abought edm.

Received Ben's book last night. Excellent! I would guess that my *applicable* knowledge base just increased ten fold over what I have been able to glean from the internet and Langlois's book.

Ben -
First: Thanks for the great book - really enjoying it and collecting the parts to build one. I saw some pictures from Roland's "CNC Woodstock" and decided I "had" to have an EDM machine. Again, really having fun collecting the parts and starting construction-------
Bob Jacoby

Hello Ben
What a great book you wrote !
My friend Dave Black and I are building a unit now. Dave met you at the Cardinal Engineering Seminar. I must say, you are a guy that warms my heart with your approach to projects. The drawer slides are a real good sub for fancy ways, and very inexpensive. The down to earth approach is just super !
I am a retired Manufacturing Engineer, and seeing this project really wet my appetite. I have built small..."Popular Mechanics" style EDMs for tap busting in the past, and always wanted a servo driven unit now I will have one.
My Best
Rich Carlstedt
Green Bay, Wisconsin

Hello Ben,
I received the book last week......
Read it in a couple of days.....
Can't wait to build an EDM!!!!!!!!!!!!
I've added it to my "To Do" List!!!
I'll try to build it the fall.
Thanks for the Book,
Tim Bostic

------I am impressed with the detail that I haven't seen since Heath Kits! Thanks for the fine job. I look forward to doing this project and will have some comments later on.
Neal Sheffield

Hi Ben,
I received my book the other day. It was a great read. I enjoyed it very much. Thank you for writing it.------
Thank you.

Code No. 011197, 170 pages, $37.00

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