Does anyone do threading on their sinker? Are there special collets made to hold these undersize electrodes so that you can just screw them out of the collet so not to loose registry with the thread?

Where is the best place to get threaded electrodes?

TMD

It has been quite a few years since I did EDM threads. Last I knew, the best source of thread electrodes was a Co. called Saturn. HTH

i always held the electrode in a v block but it is not repeatable so you cannot remove the electrode. we made our electrodes on a cnc lathe , we made them from good poco carbon rough a tap drill size hole then drop in with the threaded trod and orbit the threads.you should be able to but the theaded electrode from the carbon suppliers .

Before we got our Roboform, we would tap a block with the correct thread, lock the ram, and screw it in to the part. No servo action, so you had to "feel" the cutting. Oh, and never lean your arm on the tank-----------John

3R makes a 20MM collet chuck. That works well for holding threaded graphite rod. True, the rod doesn't fit exactly, but it's pretty close.

As far as roughing and finishing, for any fussy threads we would undersize the electrode, and make it/them on our lathe. We had a 20MM holder in the lathe chuck, so they could be made repeatable.
Threaded rod was pretty easy. If you needed a screw thread tapped 3/4 inch deep, the threaded rod would hang out a little more than double the needed thread depth. You would use the bottom 3/4 to rough, then cut off about 3/4 inch, and use the machine program to drop down .7500 and orbit out. YOU NEVER REMOVED THE THREADED ROD FROM THE COLLET FOR THIS OPERATION. We found that as long as the threads per inch was divisible evenly by the amount we dropped down in the program, the rod would line up.

Mark H

Yep, done that quite a few times over the years. We ran the threaded graphite thru a tapped plexiglass guide palte.

I found the threaded stock at Saturn Ind. , but still am wondering how to get the undersize collet made so that when I need to screw out new electrode I don't lose registration. These electrodes do not fit a std threaded hole.

TMD

The electrodes I bought had a solid shank to hold, that was tap drill diameter (IE: 1/4-20 was .201 or so, and then the threaded portion started. I just bored out a 20MM 3R shank to the dia, and put several small setscrews in to hold it. Once you start, there is no resetting or moving of the electrode in the holder. As mentioned above, you can rough, then cut off that part and finish with the remainder.. You just have to drop the Z a distance that is a multiple of the pitch. Tapered pipe threads take a little extra attention.. Really, burning threads is kinda fun..

Just to avoid confusion, I am referring to Orbiting out to thread, as opposed to the hand feed method.