How to harden drill rod?

mikey said:
Regarding O-1 vs W-1, sorry but I don't have enough experience with W-1 to tell you the difference.
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When you described putting the hot piece into the oil slowly, I wondered if there was a difference in the way you quenched oil hardening and water hardening steel. I've done very little hardening, and it's all been with W-1. In the night school class I took we were taught to plunge the heated part into the water quickly. The piece of course generated steam, almost a 'bang' and water flew everywhere at the class. On the small blades I made for a violin peg shaver, the water didn't boil out all over the place, but the blades were small.

I have been hesitant to try oil hardening steel because of the flame issue. In the past, I've heated things outdoors with my OA torch, but I'm in the process of getting a small dental kiln reconfigured to be a heat treat furnace and plan on doing any future hardening indoors.
 
I made a punch out of W-1 once to fit an odd sized hole. I used W-1 because I had a piece and the thinner nose piece warped badly. I figured it was my fault and tried again; same deal. I gave up and used O-1 and got it right the first time. Since then, I've not really used W-1. Consulting my notes, I did plunge the first piece into water and tried a slower plunge the second time - no difference in the result for me. I'm sure other more experienced users can tell you the correct way to do it but I'll stick with oil and O-1.

Re the flaming thing, I do all my hardening and quenching in my open garage. The ATF flames but doesn't splash if I go vertically and the flames self-extinguish quickly. Motor oil flames longer and produces a fair amount of black smoke so now I stick with ATF. Many ways to do this and our Mod, George, is far more experienced. Hopefully he will advise you further but I would try O-1 if I were you. It machines better and is simple to harden and temper - it has to be if I can do it!

Edit: I went back and read George's last post. I'll have to give that brine a try; I have a potato around here someplace. It won't make me use W-1 but I hate to quit on a failing note.
 
It's not the speed that the steel enters the quenchant that was being referred to as slow - the quenchant itself has "slower" cooling properties than water. Both steels should enter the quench at the same time, immersing them completely in the quenchant, and quickly from the kiln to the quenchant.
In order for Water hardening steels to harden (that's what the W Stands for), they need to be brought from their critical temperature to their hardened temperature in an absurdly short amount of time (most water quench steels are around 1450-1500 to below 1000 degrees in LESS than one second in order to transform). Oil quenching steels such as O1 are intended to harden in quenching oils, which don't cool as quickly as water, and also have less 'vapor jacket' effect at the surface of the steel in the quench. A 'vapor jacket' is where the quenchant boils and creates air pockets, acting as an insulator not allowing the quenchant to cool the steel.
O1 can take 7 seconds or longer to go from it's critical temperature to it's hardened temperature.
Most modern tool steel alloys are referred to as Air hardening, which means that their critical temperature to hardened temperature can happen so slowly it will transform in still air. Slower quenches almost always allow for less deformation in the part.

This is WAY too simplified for my tastes, but hopefully it will help clear some of this up for you guys.
 
I am a retired toolmaker after 40 years. You really do need to completely immerse your part in oil at once. If you do not,you may not get fully hardened steel all over the part,and you can also leave unseen areas of stress circling the part. Just because it seems to work does not mean you are really getting the very best results by slowly or partly immersing the part. Most of the time,for home shop use,it may not be critical how fast you quench the part,but if you want the best performance.....

It may also seem to work if you wait till the part is cold before putting it into an accurately controlled tempering oven. You are not getting the best possible performance out of the steel. That means you are getting less long range wear resistance,and incomplete molecular formations in the steel.

I have mentioned here and elsewhere,01 is a better all around tool steel to use than W1. W1 is very treacherous. For example,If I make a letter stamp from a piece of W1 that is 2" long and 1/4" square,and harden its whole length,invariably the stamp will crack open down its length. That won't happen with 01 since it cools slower in oil. I only harden about 1/2" of the business end of letter stamps.

The main advantage of W1 is it will take a keener edge than any other tool steel. It won't hold the edge as long,but it will get sharper.

We used to have a 5 gallon ATF quench in the tool maker's shop I ran. Yes,there will be some flame,but just use long tongs. No problem. The fire soon goes out,especially when the part is fully submerged. We had a powerful exhaust fan above the quench to keep soot from getting all over the shop. The smoke should be your biggest concern if you have a neatly painted shop,OVER TIME,your paint can start getting dirty(Not all at once!). So,if you can have an exhaust fan over the quench(We also had a big hood we made. That helped,too). Your shop will stay clean longer.

I'm only mentioning the soot because I assume most of you have shops in the basement,or in the garage where your wife would not appreciate soot!!:) There is nothing to be afraid of with a little flame up. Like I said, USE LONG TONGS. Ours were standard blacksmith type tongs less than 2 feet long. That was long enough to keep our hands well away from even the largest parts we quenched. The largest things we quenched were woodworking plane irons 4" wide and about 12" long,and 1/4" thick,for large molding planes. Even those were not dangerous to quench. Use long tongs,keep your face low. Wear goggles or a shield.
 
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Thanks for all of the information. This has been the best practical discussion of heat treatment that I've read.
 
I'll give your recommendations a try, George and Matthew. I go from heating to immersion immediately but can certainly immerse faster. As for tempering soon after removing from the oil, that I can try. I'll be interested to see how hard or easy it is to clean the part after tempering vs doing it before I temper.

You're right George - because something has worked doesn't mean it can't be done better ... or properly. I'll keep you advice and experience in mind.

Matt, I may give W-1 another try just to see if I can get it to work for me. Thanks for the info.
 
Mikey,if you get some PBC NO SCALE from Brownell's gunsmitjing you can make your parts nice and clean through the hardening process. I have made manny riffler files,and always use it to keep the cutting edges of the file teeth from getting dulled.

Your parts will clean up looking very bright. You heat the part to harden and get it to a brown or blue color. Then,roll it in the PBC,which melts all over the part. When you quench the part in water,the PBC flies off. For oil quenching,it is still on the part,but loosened by the quench,and easily wiped off.

I have made a thick batter of flour,some yeast,and a little salt,to dip the part in. It is an old 19th. C. recipe that works fine,but smells like burnt bread(which it is!) Stubbs file co. in the 19th. C. in England,dipped their files in "beer leavings" before hardening. The old timers always knew how to get by cheaply as money was tight.

The trouble with the wheat recipe is you can't save it! Fun to try,though. A thick layer of carbon is left on the part. Not quite as nice as PBC,but does the job. You can also dump the part in boiling water to get rid of the burnt PBC after hardening.

MSC sells some similar stuff. Don't buy it. It's horrible. Melts and runs,making an uneven,messy surface when hardened. I warned them,probably to no avail.
 
I'll order up some PBC the next time I need to harden something and give it a try. That bread recipe sounds really cool and I may try that just for the education.

Thank you, George! I love learning new stuff!
 
I'll second George's observation on PBC. LOVE the stuff. I do lots of low temperature thermal cycles on my simple carbon steel blades to reduce and refine grain, and PBC keeps the steel from decarbing through the process. Messy, but worth every penny!
 
P.S.: If you use the same station for soldering stuff,be sure to not leave any PBC on your fire bricks where you might silver solder. It makes the most wonderful flux,and you will have solder running all over the places that you got stray PBC on!!
 
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