View Full Version : O1 tool steel

03-19-2012, 02:10 PM
Is there any major problems with using a torch to harden O1 3/8" thick? I made some small blades for a cutter to used on plastic and occasionally wood and now I need to harden and temper them before use, the plan is to torch heat to dull red then oil quench followed by 400 deg temper for 1 hour. Will this work ok? The dull red is to prevent scaling but will that be hot enough?

Please bear with me, I know I have asked several questions about hardening and tempering but I am still learning and I have not yet tried O1 tool steel, these parts were hard to make and I don't want to ruin them at this point.

03-19-2012, 02:29 PM
Dull red will not get you there. You need to get to bright orange with white spots. Get it heated evenly so it looks the same all over, then quench.
I think the white (or yellow) spots are the carbides in the steel, not sure, but when they start to appear you are at the correct temp for that tool steel. This works for most common tool steels (for me anyway). After quenching, if the steel has been hardened it will be a gray color.
I like to double temper, once at the desired temp, cool, then again at 25 to 50 degrees lower temp.

03-19-2012, 03:44 PM
Use a magnet to figure out when you reach the critical point.

As for tempering, I'd use a lower temperature if you don't want to drop hardness too much. Sometheng like 300F for 20-25 minutes will be enough for 3/8" thickness (one hour per inch of the smallest dimension).

03-19-2012, 04:30 PM
Ok, looks as if I had it all wrong but then that's why I asked.

Thanks guys

03-19-2012, 04:44 PM
Wrap in a bit of stainless foil with a scrap of paper to prevent scaling. The paper chars and burns up the O2 in the package. Quench the piece while in the pouch then remove the foil.

03-19-2012, 05:27 PM
I'd avoid quenching in the pouch to prevent uneven quenching/soft spots.

03-19-2012, 06:47 PM
My attempts with a little propane plumbers pencil torch failed to harden 1/2 O-1. Have a bigger MAPP torch now but have yet to try it...

I've heard reports of folks using O-1 dead hard, no temper at all. Probably depends on what you're using it for.

03-19-2012, 10:30 PM
It is normally recommended to temper (draw) the part after hardening. Some of the stress created in the hardening process can cause problems if not treated.

03-20-2012, 01:13 PM
Radkins - O-1 is a very forgiving steel. It hardens at 1475 deg. F or about 800 deg. C. Heat to a bright cherry red and quench in oil. To avoid warpage try to immerse straight down, not putting it in with the flat side first. After letting it cool in the oil clean it with emery so you have a shiny surface over most of the part. Now , using a softer flame start to apply heat and watch the color's. It will start with a light yellow and than turn to straw yellow, orange, light brown, brown, light blue and blue. You want a straw yellow to light brown. Now immediately quench in oil again.
A electric hot plate works very good on larger parts.
If your part is small you may heat the section needing hardness only, quench, clean to a metallic finish and than use a soft flame to draw the color from the section not hardened on up to the desired color on the tip.
Sound a little complicated - but with just a little practice you will succeed.
To practice use a section of 3/16 or so O-1 drill rod. sharpen the tip and than heat (the tip) cherry red. Quench. Make it shiny and draw from the bottom to the tip. Quench when the tip turns straw yellow to light brown and now you have a nice scriber. Watch out - on thinner sections the color can run (change) very fast.
If it does not work out the first time and the tip turns blue (soft) - just start over again using the same part. After a few practice runs you will know exactly what to look for. Good luck.

03-20-2012, 04:31 PM
For sure I was about to do it all wrong before I asked here and I'm really glad I did! Thanks a bunch, before attempting to harden the blades I will practice on a couple of small pieces I had left over.

03-20-2012, 06:30 PM
You do NOT let it COOL. When it reaches a temperature you can BARELY hold,put it into a pre heated toaster oven. This is austempering. You will get better life out of your edges that way. I use a toaster oven with a high temp. thermometer inserted into it with its long probe. The thermometer the ovens come with are not accurate. And,kitchen ovens can run 75 too hot. Tempering is critical,and you only have a 25 "window" to get optimum results.

The magnet thing works for hardening,but you also need to get control of your tempering temps too.