Re: [CAD_CAM_EDM_DRO] Tap burning EDM? Need it Quick and Dirty ;-)

jmkasunich wrote:

>Turn, Turn, Snap... Arrgh!
>
>Busted an 8/32 spiral flute tap in a piece of A2 tool steel
>last night. I want to try the EDM approach to get it out.
>
>I checked out Jon Elson's EDM page at
>http://pico-systems.com/edm.html
>
>The electrical side is no problem, I've got a 48V 10A
>unregulated DC supply (for my CNC shoptask project), and
>a Variac, and enough other parts to make the sparker.
>I've got enough electrical knowledge to avoid shocking
>myself or frying something.
>
>The electrode holder is no problem, I can cook up something
>simular to Jon's. The problem is the electrode feed. Jon
>used his CNC mill to spin and advance the electrode. I don't
>have a CNC mill (yet). I have a drill press that will go
>slow but doesn't have a fine feed. I have the Shoptask mill,
>which has a moderately fine vertical feed, but won't go slow.
>I could also use the Shoptask lathe function, feed is better,
>but I don't know how to keep the fluid around a horizontal
>electrode. I could also try to build something specifically
>for this job - a piece of 4-40 threaded rod would give a finer
>feed than any of my machines, but gets away from the "quick
>and dirty" approach. I don't want to spend several days
>getting this tap out.
>
>It seems that anything simple that I can come up with will
>require manual electrode feed. Is it practical to use
>manual feed to burn out about 3/8" of a #8 tap? Or is slow,
>smooth advance of the electrode too difficult to do?
>
>

Yes, all the tap burning I've done has been manual. The CNC system
actually did the
moving, but I was there the whole time, pushing the jog buttons, mostly.
Without the
flushing of chips, I had to stop and back up very often. If you can rig
some brass tubing
and use an elevated can of EDM fluid, you may have much better results.
I am going
to do this the next time a tap needs to be burned out.

As for really fine feeds, leaning on the machine may do it! I actually
modulated the
arc by leaning on the head of my Bridgeport mill!

Jon