Date:         Sat, 14 Jul 2007 09:04:58 -0700
Reply-To:     Evan Mac Donald <macdonald1987@SBCGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Evan Mac Donald <macdonald1987@SBCGLOBAL.NET>
Subject:      Re: exaust removal woes
In-Reply-To:  <0JL600GG4DXWYUS7@vms048.mailsrvcs.net>
Content-Type: text/plain; charset=iso-8859-1

The process is usually called "EDM" and should be easier to find if searched for that way. Basically, a high-energy arc discharge is used to vaporize the metal at the point of the electrode. Kind of like arc welding in reverse. Many prototype parts shops use this process to cut metal plate, and also to bore small diameter, deep holes. Since there is no actual "bit" removing the metal, it cannot break off and get stuck. Changing the voltage / amperage parameters allows for better removal of different materials. It may be cheaper, though, to get a new head...

pdooley <psdooley@VERIZON.NET> wrote:  Even "good" bits will have a heck of a time drilling through a tungsten
carbide drill bit.

The one method I have heard about to do this is spark erosion.
Apparently some kind of device is hooked up which sends a concentrated spark
through the broken off bit and erodes it away.
Sounds pretty slick, but that's all I know about it.
I have never seen it done or know about equipment availability.


-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
dylan friedman
Sent: Friday, July 13, 2007 10:36 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: exaust removal woes

to do it the right way and have it work when you are finished, the head
should come off and use a drill press and good bits to make a hole for an
extractor. I have had similar issues in the past. I don't mess with it in
the van. I pull them and do it so it will last and not make matters worse.

dylan

craig cowan
wrote: So today my day at work started
as any would (except discovering the trash
truck put a sizeable dent in the nose of the vanagon......which will be
repaired free of charge), and the mecahnics at my work started working on my
vanagon. I popped in from time to time to check the progress. The goal was
to replace the manifold gasket at cylinder 1, so the manifold had to come
off as the studs were damaged. Of the 4 bolts that connected to the heads
and 2 that connected to the collection pipe (1.9L) The collection pipe bolts
came right off, and 3 of the head nuts. One was not so lucky. It snapped and
the mechanic welded a nut to the stud and started backing it out.....it was
working really well....till it broke the stud halfway inside the head.
So......out comes the tungsten carbide drill bits.......a very accurate and
perfectly executed drilling went horribly wrong when the bit broke off flush
with the head. "You cant drill out a drill bit" boss mechanic said.....so
over the course of the weekend the entire staff is trying to figure out how
to fix this without removing the head (or even if the head comes
off.....what do you do?)

Sudgestions so far include "Burn it out" though i dont know how, "Stronger
Drill Bits" which are on order but have low expectations, and "replace the
head".

Any ideas are greatly appreciated!!!!!!

-Craig
'85GL (which isnt having its best day)