Hardening a Disc

[Splat]

Guys, I made Rick Sparber's lathe tool height gauge . I made this disc that the lathe tool comes up underneath to to check height from 1045 steel. It's 0.50" thick, 2.0" in diameter with a 0.75" hole. It has a 1/4" threaded hole in the side for a set screw to secure the disc to its post. After making the gauge I thought about hardening at least the face of the disc so my lathe tools don't mar the face. I've never heat treated any steels before and don't have a forge. I thought about simply getting a hardened washer and epoxying it to the underside of the disc but was wondering if I could do something better. Should I get the face red hot and quench or make another disc out of A2 or W1 (which I have none of)? What would be a good way of going about this? Thanks.

 

[mikey]

Why not make the disc from O-1 steel? It has twice the carbon content of 1045, is easily heat treated in the home shop with simple equipment (Mapp gas torch), is fairly resistant to warping with heat and is simple to temper if desired. In the annealed state, it is also simple to machine and get decent finishes with.

 

[benmychree]

Your 1045 steel will harden sufficiently to be wear resistant, as quenched in water, it should make about 54 Rc, if tempered at 400F it would be about 51Rc; heat to 1525 - 1575 F. Best to heat through with even color all over.

 

[MrWhoopee]

^^^^What John said. In the absence of any way to check the temperature, the steel will lose it's attraction to a magnet when it's hot enough. Heat to cherry red, quickly quench and agitate.

I made my tool height gage from aluminum, including the disc. It seems to be holding up just fine. I put a very potent rare-earth magnet in the base so it stays where I put it.

 

[benmychree]

I have never had to use the magnet trick, I always had access to a temp controlled heat treating oven and draw pot, it certainly is a good procedure for home shop use and blacksmithing.

 

[Splat]

Thanks guys. I'll give the Mapp torch and water quench a shot. Or, I may just toss the guts and just set the top of the disc to center line and simply run finger over the tool and disc. Easier. It's amazing how sensitive our digits are.

 

[Oskar_]

Buenos días, yo lo calentaría con un soplete hasta dejarlo en color rojo cereza y luego enfriaría la pieza lentamente cubierta con arena de playa por ejemplo.

 

[Jake M]

After making the gauge I thought about hardening at least the face of the disc so my lathe tools don't mar the face.

I do NOT want to knock the wind out of your sails on a project you're looking forward to. From a functionality perspective however, let me suggest that wile you WILL see marks, it will probably take you decades to wear that down enough to affect it's function or accuracy. My home made one has WAY less surface area than yours, to spread out the wear, it's made of aluminium, and it's not suffering any loss of accuracy. That includes primarily ground high speed steel tools, which scratch far worse than generic carbide tools. (There ARE some VERY sharp carbide tools that would match what the HSS does). But aside from visual imperfection (in a place you can't see)... I can't see a harm in leaving it as it is.

If you WANT to do this- I'd highly suggest that you harden the WHOLE part. In a makeshift setup, if you try to harden one face, you're going to (most likely) warp the part by a large enough amount that it will affect it's functionality. You could of course sand and polish that out, it won't be "that much". Heat it equally, slowly, so it warms up the same all the way to the middle, supported by wire so that you can drop it straight into your quench, and while it's in there, keep it moving.
There would be no harm or compromise in leaving the piece "glass hard" after the quenching. Tempering "could" be done to make it tougher, but it's not really subject to that kind of use where it would matter. Unless you want to use it for a hammer. Then tempering it back "some" could be of use. But not required for setting tool height. In the fully hardened state, it won't cut the tools, and the tools won't cut it.