Hardening Gauge plate

Any tips?
Wikipedia says "Gauge plate is a special kind of carbon steel, manufactured to exact dimensions, and delivered in annealed state. It can be hardened by heating to a specific temperature, the Curie point, and quenching in water or oil."
Does that mean heat it until it's no longer magnetic (perhaps easy to test for using a magnet - as long as the magnet has a higher Curie point, I suppose)?
The stuff I have says "oil hardening" on the outside, but what sort of oil should I use?
Is it like silver steel, which I have hardened - does it then need tempering? I want it as hard as is compatible with use as tooling, think eg a mill clamp set or tee-nut, something like that.
As I said, any tips welcomed. Thanks,
-- Peter Fairbrother

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You don't have to heat the magnet. I use a rather weak telescoping pocket pick-up magnet. The length makes it sensitive to a slight pull, like feeling a nibble with a fishpole, but it isn't strong enough to shift the workpiece in the fire.
The Curie point isn't exactly the best hardening temperature so let the steel get a little hotter. Not everything happens instantly. http://www.navaching.com/forge/heat.html
jsw

On Thu, 9 Dec 2010 14:01:01 -0800 (PST), Jim Wilkins
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Your rather weak telescoping magnet probably uses the old alnico type magnets which are pretty tolerant to heat up to a few hundred deg C.
Pretty well all modern telescoping magnets use a type of rare earth magnet which degrades rapidly at much over 80 deg C.
However they are so much stronger than the old alnico types that they can be used with a short mild steel extension - about half the diameter of the magnet and a few diameters long.
The mild steel is then OK up to a several hundred deg C and the magnet stays comparatively cool.
Jim

On Dec 10, 8:44 am, snipped-for-privacy@yahoo.com wrote:
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The test is so quick that I just did it without harming a plastic- coated magnet. I had to grab the red-hot nail with tongs so the magnet wouldn't pull it out of the fire.
jsw

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I forgot to mention that only one end was red hot and non-magnetic.
jsw

"Peter Fairbrother" wrote in message
Any tips?
Wikipedia says "Gauge plate is a special kind of carbon steel, manufactured to exact dimensions, and delivered in annealed state. It can be hardened by heating to a specific temperature, the Curie point, and quenching in water or oil."
Does that mean heat it until it's no longer magnetic (perhaps easy to test for using a magnet - as long as the magnet has a higher Curie point, I suppose)?
The stuff I have says "oil hardening" on the outside, but what sort of oil should I use?
Is it like silver steel, which I have hardened - does it then need tempering? I want it as hard as is compatible with use as tooling, think eg a mill clamp set or tee-nut, something like that.
As I said, any tips welcomed. Thanks,
-- Peter Fairbrother
Raw linseed oil works quite well for any oil hardening steel. Others have experienced good results with motor oil. Do not use boiled linseed oil!
Steve R.

writes
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Just out of pure curiosity, Steve - why not?
David

On 12/10/2010 4:24 AM, Peter Fairbrother wrote:
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Gauge plate is basically flat stock silver steel as far as I'm aware
I use used motor oil to quench my silver steel . With large fat pieces you need to be aware that some distortion may occur when quenching . The water hardening stuff requires a brine of water and salt or some type ,I,m led to beleive . I only ever use 01 silver steel(oil hardening) because I can't be botherd messing around making a brine.

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From a quick google, gauge plate may be O1 tool steel, a carbon manganese steel like silver steel, but with a spot of tungsten and vanadium.
For "home use", the hardening and tempering would be the same as for silver steel.

"Peter Fairbrother" wrote
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Doesn't your gauge plate come in a wrapping with hardening and tempering data printed on the label.
To quote a "Macreadys" label
To Harden
Quench in oil at 780 - 820C According to size - Rockwell C63-64
Temper for one Hour
150C to obtain 62 Rockwell C 200C to obtain 60-61 Rockwell C 250C to obtain 58-59 Rockwell C 300C to obtain 56-57 Rockwell C

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Heat it to cherry red for one minute of each inch of thickness to allow time for the crystal changes to occur, then quench in oil or water. It doesn't matter what sort of oil, so I use old motor oil. The important point is that oil will not boil, unlike water which forms an insulating layer of steam around the work which slows the cooling rate.
Cliff Coggin.

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Some folks use motor oil to quench but I use cooking oil.
Supermarket "own brand" will suffice - cheap as chips (no pun intended) for a large bottle..
As the oil is required to be able to stand higher temperatures, there is less chance of it catching fire - especially if only a small quenching tank is used. Always make sure you have a substantial amount of oil in the quenching vessel.
I find that cooking oil generally has a lower viscosity than many motor oils which I find aids cooling. Also, I find less discolouration of the parts.
Whether or not to temper depends on the item being made.
Regards,