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

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

You could wave a magnet in its vicinity.

No kidding -- I have successfully demagnetized screwdrivers with a
strong permanent magnet. Stroke it a few times with one pole, then
reverse the magnet and stroke it a bit further away. Keep doing this
until you're waving the magnet in the air well away from the part.

It _won't_ demagnetize the thing completely, and may not work at all for
complex shapes, but it should make things better.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

On Thu, 23 Mar 2006 09:25:40 -0800, Tim Wescott wrote:

Stroke it a few times with one pole, then
reverse the magnet and stroke it a bit further away. Keep doing this
until you're waving the magnet in the air well away from the part.

I'll give that a shot, thanks.

It _won't_ demagnetize the thing completely, and may not work at all for
complex shapes, but it should make things better.

Well, right now it's not that complex of a shape, but it will be
shortly. I'll demag it first then.

Thanks
Dave

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

"Tim Wescott" wrote: (clip) Stroke it a few times with one pole, then
reverse the magnet and stroke it a bit further away. Keep doing this until
you're waving the magnet in the air well away from the part. (clip)
^^^^^^^^^^^^^^^^
You are, in effect, producing a gradually diminishing AC field. which is
what a degaussing coil does. As you say, it might be only partially
effective, and it would take time. How about wrapping a coil in your steel
bar, and applying a little AC voltage, and then reducing that, with a
Variac? Or look around for an existing coil to use? Lots of mechanical
devices use solenoids to make things move--for example, the automatic locks
on car doors. The important thing is, you need to produce a field that is
as strong as the one in the piece of steel, that reverses a lot of times,
getting gradually weaker and going to zero.

Easy, if you have a D C welder. Simply wrap the lead around the piece
several times and hold it in a dead short. Check the piece and if it's more
magnetized, just reverse the polarity and short again. Keep doing this until
the magnetism is gone. Learned this from an old railroad man back in the
50's and it worked
Walt.
"RoyJ" wrote in message
ink.net...
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

"E. Walter Le Roy" wrote in message
news:V1CUf.10331$TK2.3359@trnddc07...
Easy, if you have a D C welder. Simply wrap the lead around the piece
several times and hold it in a dead short. Check the piece and if it's
more magnetized, just reverse the polarity and short again. Keep doing
this until the magnetism is gone. Learned this from an old railroad man
back in the 50's and it worked

It just seems intuitive that it would work better with an AC welder. The
tool MAGnetizer I used to have used a DC coil in dead short with a
consummable fuse to break the circuit rapidly, and cause a strong 'ring' in
the coil as the field collapsed.

Breaking the short on a DC welder might even strengthen the magnetization of
the piece. Reversing the polarity doesn't guarantee that you'd not swing
the work to the opposite polarity, leaving it still magnetized.

LLoyd

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?

How big is the part? For very small parts, I use a Weller soldering
gun, the
kind with the two posts sticking out the front, and the copper "wishbone".
If necessary, I can make a ring of #12 wire that has a bigger opening than
the standard element.

For larger pieces, do you have an AC TIG welder? If not, then try an AC
buzz-box. Make a loop of several turns of ground cable big enough to
surround the part, and short the electrode holder to the ground clamp.
If TIG, set it for something like 50 A, if buzz-box, set it for the lowest
current possible. Place the looped cable around the part, and turn on the
welder, or step on the TIG pedal. Remove the cable while the welder
is still on, then turn it off when the cable is away from the part. You
may have to repeat this process several times in different starting
orientations to completely demagnetize the part. You may have to turn
up the current if the amp-turns are not enough to do the job.

What you are doing here is passing an AC electromagnet over the part,
and gradually drawing it away. The 60 times per second alternating
field of decreasing intensity gradually reduces the remanent field to
zero. (When I say gradually, it only takes a couple of seconds.)

Jon

On Thu, 23 Mar 2006 13:33:13 -0600, Jon Elson wrote:

Dave Hinz wrote:

So how do I demag this sucker?

How big is the part?

Roughly 8" x 1.056" x 1.200" before I started removing chunks, curls,
& chips...

For very small parts, I use a Weller soldering
gun, the
kind with the two posts sticking out the front, and the copper "wishbone".
If necessary, I can make a ring of #12 wire that has a bigger opening than
the standard element.

Doesn't apply in this case, but thanks, I do have that type of Weller
iron (along with 3 other Weller irons - all surplus but good stuff)

For larger pieces, do you have an AC TIG welder? If not, then try an AC
buzz-box.

I've got a neighbor who is a blacksmit, I bet he can help me out on this
one. Thanks.

What you are doing here is passing an AC electromagnet over the part,
and gradually drawing it away. The 60 times per second alternating
field of decreasing intensity gradually reduces the remanent field to
zero. (When I say gradually, it only takes a couple of seconds.)

Right, so I'm inducing a bias frequency as a B1 to change the B0. Funny
how I tend to forget that all that schooling translates into real world,
sometimes. I guess it's because so many times it doesn't.

Leo Lichtman wrote:

"Tim Wescott" wrote: (clip) Stroke it a few times with one pole, then
reverse the magnet and stroke it a bit further away. Keep doing this until
you're waving the magnet in the air well away from the part. (clip)
^^^^^^^^^^^^^^^^
You are, in effect, producing a gradually diminishing AC field. which is
what a degaussing coil does. As you say, it might be only partially
effective, and it would take time. How about wrapping a coil in your steel
bar, and applying a little AC voltage, and then reducing that, with a
Variac? Or look around for an existing coil to use? Lots of mechanical
devices use solenoids to make things move--for example, the automatic locks
on car doors. The important thing is, you need to produce a field that is
as strong as the one in the piece of steel, that reverses a lot of times,
getting gradually weaker and going to zero.


Yes, it takes time -- but less time than buying or building the right tool.

Were I to do it all the time I'd get or make the right tool.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

Dave Hinz wrote:

On Thu, 23 Mar 2006 13:33:13 -0600, Jon Elson wrote:


Dave Hinz wrote:



So how do I demag this sucker?



How big is the part?



Roughly 8" x 1.056" x 1.200" before I started removing chunks, curls,
& chips...



For very small parts, I use a Weller soldering
gun, the
kind with the two posts sticking out the front, and the copper "wishbone".
If necessary, I can make a ring of #12 wire that has a bigger opening than
the standard element.



Doesn't apply in this case, but thanks, I do have that type of Weller
iron (along with 3 other Weller irons - all surplus but good stuff)

I really think that you CAN do this with a Weller gun. You will need to
make a
custom copper coil to fit around the part, but it will work on something
this
size. You need a coil about 1.5" diameter, with one or two turns. Hold
the part
at the very end with pliers in one hand, and turn on the soldering gun.
Pass
the part through the copper loop all the way, then draw it back fairly
slowly,
so it takes several seconds to pass all the way through the coil. When
the part
is at least 6" away from the coil, turn off the soldering gun. The part
will
definitely be demagnetized. This procedure will degauss anything but a
high-
strength permanent magnet.

I use this setup all the time to degauss small tools that occasionally
pick up a
strong magnetism.



Jon

"Dave Hinz" wrote in
message ...
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

Electric motor rewinders have a test unit
commonly called a "growler". This was for testing
armatures and was basically a coil with poles
pieces. I used to use one to demagnetise any
rotating part of our equipment when working in the
oil well logging industry. Easy to use, we just
turned on the switch while some distance from the
part, moved close to the part and held it for a
while then backed away before shutting it off. It
was usually successful, though I heard that one of
the trucks had been hit by lightning and had to be
scrapped, as it not be demagnetised to an
acceptable level.

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

"Dave Hinz" wrote in message
...
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

Dave
TV repair shops often have degaussing coils used to remove any magnetism
from TV tubes; it's worth a shot if you're friendly with a TV repair man.
Martin
--
martindot herewhybrowat herentlworlddot herecom

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

How big a part?

An AC coil is the answer in any case. Preferably one that you can hold
the part in and then draw it away from while the coil is still active.

For small items, the frame les the rotor of a cheap fan or blower motor
will work fine, just place the part oin the feild between the poles and
withdraw it slowly away.
A bunch of wraps of wire and an AC welder would serve for larger items.

Guys to talk to. Engine rebuild shops that magnaflux cranks or heads.
The unit they use (Parker Probe, pretty commonly
http://www.parkreshcorp.com/) can demag as well as magnetise, and is
quite portable.
Non Destructive Testing or Inspection NDT/NDI shops. A fixed Mag
particle bench can run several hundred amps through it's coils. (Leave
your credit cards in the changeroom, or else. Watches too!) Typical coil
on a fixed bench unit should allow you to run a decent sized lunch box
through it.

Watchmakers, clockmakers. Magnetism is a very bad thing, so they demag
parts and tools as required. A little AC coil again, sometimes in the
form of a coil, sometimes the coil is buried in a nice flat plate that
looks like a small benchtop weigh scale. In either case the part is
placed in the field and draw away slowly to minimise the chance of
imparting a bit of magnetism into the part as the field collapses.

Cheers
Trevor Jones

"Dave Hinz" wrote in message
...
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


If you have some grinding left to do on it, wrap a heavy extension cord [the
longer the better] around it, plug in the grinder, and go to work on it.

By the time you're ready to reposition it for the next round [having, I
hope, NOT ground through the wire...], the piece should be degaussed.

Otherwise, just run a piece of machinery that's plugged into the coiled cord
and, periodically, check the level of magnetism in the piece.

On 23 Mar 2006 17:01:07 GMT, 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


Got a welder? Wrap one lead around the piece, on AC and strike an arc
with the stinger in a piece of scrap on high amps

Gunner


"The importance of morality is that people behave themselves even if
nobody's watching. There are not enough cops and laws to replace
personal morality as a means to produce a civilized society. Indeed,
the police and criminal justice system are the last desperate line of
defense for a civilized society. Unfortunately, too many of us see
police, laws and the criminal justice system as society's first line
of defense." --Walter Williams

On 23 Mar 2006 20:21:32 GMT, Dave Hinz
wrote:

On Thu, 23 Mar 2006 13:33:13 -0600, Jon Elson wrote:

Dave Hinz wrote:

So how do I demag this sucker?

How big is the part?

Roughly 8" x 1.056" x 1.200" before I started removing chunks, curls,
& chips...

For very small parts, I use a Weller soldering
gun, the
kind with the two posts sticking out the front, and the copper "wishbone".
If necessary, I can make a ring of #12 wire that has a bigger opening than
the standard element.

Doesn't apply in this case, but thanks, I do have that type of Weller
iron (along with 3 other Weller irons - all surplus but good stuff)

For larger pieces, do you have an AC TIG welder? If not, then try an AC
buzz-box.

I've got a neighbor who is a blacksmit, I bet he can help me out on this
one. Thanks.

What you are doing here is passing an AC electromagnet over the part,
and gradually drawing it away. The 60 times per second alternating
field of decreasing intensity gradually reduces the remanent field to
zero. (When I say gradually, it only takes a couple of seconds.)

Right, so I'm inducing a bias frequency as a B1 to change the B0. Funny
how I tend to forget that all that schooling translates into real world,
sometimes. I guess it's because so many times it doesn't.



Every colour TV is fitted with a demagnetising coil
which is designed to do just that when connected to normal
50/60Hz power.

Raid a junk TV for this coil which is wrapped round the
large flare of the display tube. As removed it is a large
diameter coil. Twist the coil so that it is re-arranged into a
three turn loop (this is the same trick as twisting a vee belt
into a three turn loop to make it smaller for storage).

You now have a very convenient demagnetiser - pass the
workpiece slowly (a second or so) through the coil and it will do
a thorough demagnetising job. The coil is short time rated so
don't leave it on too long - 10 to 20 sec is OK.

Jim


--
Posted via NewsDemon.com - Premium Uncensored Newsgroup Service
-------http://www.NewsDemon.com------
Unlimited Access, Anonymous Accounts, Uncensored Broadband Access

On Fri, 24 Mar 2006 10:10:22 +0000, wrote:

On 23 Mar 2006 20:21:32 GMT, Dave Hinz
wrote:

On Thu, 23 Mar 2006 13:33:13 -0600, Jon Elson wrote:

Dave Hinz wrote:

So how do I demag this sucker?

How big is the part?

Roughly 8" x 1.056" x 1.200" before I started removing chunks, curls,
& chips...

For very small parts, I use a Weller soldering
gun, the
kind with the two posts sticking out the front, and the copper "wishbone".
If necessary, I can make a ring of #12 wire that has a bigger opening than
the standard element.

Doesn't apply in this case, but thanks, I do have that type of Weller
iron (along with 3 other Weller irons - all surplus but good stuff)

For larger pieces, do you have an AC TIG welder? If not, then try an AC
buzz-box.

I've got a neighbor who is a blacksmit, I bet he can help me out on this
one. Thanks.

What you are doing here is passing an AC electromagnet over the part,
and gradually drawing it away. The 60 times per second alternating
field of decreasing intensity gradually reduces the remanent field to
zero. (When I say gradually, it only takes a couple of seconds.)

Right, so I'm inducing a bias frequency as a B1 to change the B0. Funny
how I tend to forget that all that schooling translates into real world,
sometimes. I guess it's because so many times it doesn't.



Every colour TV is fitted with a demagnetising coil
which is designed to do just that when connected to normal
50/60Hz power.

Raid a junk TV for this coil which is wrapped round the
large flare of the display tube. As removed it is a large
diameter coil. Twist the coil so that it is re-arranged into a
three turn loop (this is the same trick as twisting a vee belt
into a three turn loop to make it smaller for storage).

You now have a very convenient demagnetiser - pass the
workpiece slowly (a second or so) through the coil and it will do
a thorough demagnetising job. The coil is short time rated so
don't leave it on too long - 10 to 20 sec is OK.

Jim

Like coiling a bandsawblade. Clever!

You need a coil of wire!--with a hole big enough to pass your bar
through it..heavy wire--like 12 or 16 gage--more turns the better
hook up a duplex outlet recepticle in series with it--plug in a couple
of clothes ironing irons, or a space heater --something that will draw
1000 watts or so(so you don't burn out the coil)-plug it in & pass the
bar through it --and on past it. I have a primary coil out of an old
neon sign transformer that I've been using for many years.

NOTE--WHEN THE COIL IS FILLED WITH IT'S LAMINATED IRON CORE, IT DRAWS
PRACTICALLY NO CURRENT--WITHOUT THE IRON CORE IT WILL BURN OUT VERY
QUICKLY. THAT'S WHY YOU LIMIT THE CURRENT WITH THE IRONS, OR HEATER
RESISTANCE ELEMENT. JJW





Tom Miller wrote:

"Dave Hinz" wrote in
message ...

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


Electric motor rewinders have a test unit
commonly called a "growler". This was for testing
armatures and was basically a coil with poles
pieces. I used to use one to demagnetise any
rotating part of our equipment when working in the
oil well logging industry. Easy to use, we just
turned on the switch while some distance from the
part, moved close to the part and held it for a
while then backed away before shutting it off. It
was usually successful, though I heard that one of
the trucks had been hit by lightning and had to be
scrapped, as it not be demagnetised to an
acceptable level.

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



We used a big 3 phase motor with the rotor removed and hooked up the
windings to 110AC. You just pass the metal through the opening where
the rotor was and it will be demagnitized.

John

writes:

An AC coil is the answer in any case. Preferably one that you can hold
the part in and then draw it away from while the coil is still active.

For small items, the frame les the rotor of a cheap fan or blower motor
will work fine, just place the part oin the feild between the poles and
withdraw it slowly away.

Another source: a magnetic tape demagnetizer. Radio Shack used to sell
a handheld version of this; it was a coil with an iron core and the core
face was just inside the bottom of a plastic case. You turned it on,
placed it against the tape to be demagnetized, moved the tape around a
bit, then pulled the tape away before turning off power. I've used
this for demagnetizing all sort of tools, and if anything it's too
strong - large masses of metal are attracted with a lot of force.

They used to be something like $30, but I recently found one at a thrift
shop for $2.

Then there are industrial tape demagnetizers with a coil large enough to
pass a whole open reel of magtape through.

Dave

"RAM³" writes:

If you have some grinding left to do on it, wrap a heavy extension cord [the
longer the better] around it, plug in the grinder, and go to work on it.

By the time you're ready to reposition it for the next round [having, I
hope, NOT ground through the wire...], the piece should be degaussed.

This won't work. The extension cord contains two conductors with equal
and opposite currents at all times, so the magnetic field produced by
the cord is almost nil.

You *could* do this by making up an "extension cord" using two single
conductors, and wrapping one conductor into a coil while the other conductor
bypasses the coil. Or put both conductors in the same coil, but wind
one wire clockwise and the other counterclockwise.

Dave