View Single Post
  #4   Report Post  
Posted to rec.crafts.metalworking
RoyJ
 
Posts: n/a
Default demagnetizing 4140?

Put it in an AC magnetic field. I have a 500' coil of 14 ga TW building
wire, hook it to the AC output of a heavy duty battery charger.(you have
to go inside to find the lead) Resistance is a bit over an ohm, would
draw about 9 amps on 12 volts. Shoudl be a big enough coil for your
part. It might have to sit there for a few minutes.

Dave Hinz wrote:
Building a project out of a piece of 4140 prehard. The local custom
metalcutting shop provided the steel. Problem is, it's magnetic. Not
just a little magnetic, it's "you could use this thing to pick up nails,
small children, and battleships" magnetic. I asked them if they have a
demag ring, they don't (and were surprised but will check their stock...
ok, great, but doesn't help me much at the moment).

So how do I demag this sucker? I know that heat would do it, but I
don't want to mess up my hardening. I know mechanical impact can redue
it, but I don't know if that's one of those "theoretical but not
practical" things, or if it'd work. So, simple question - can I just
smack the (un-machined) end of this sucker with a hammer a bunch of
times and get it down to tolerable, or do I need to find someone with
degaussing apparatus of some sort, or am I SOL? It's annoying, to say
the least, to have every chip re-attach itself to the work, invariably
on the layout lines that I'm trying to see.

Thanks,
Dave Hinz