quenching medium

[allen long]

George you are correct, Sir. And not just a matter of semantics. In my zeal to make a point I should have said, the reason you anneal something is to relax / relieve the molecular stresses to make it tough, not to soften the steel. I believe the metallurgical world is always looking for that magic alloy and process combination that will yield a steel that is as hard as possible while still being tough (not brittle). There is always a trade-off between absolute hardness and toughness. We have not even talked about grain structure for sharpness! George, as a professional, is O1 the best bet for the serious home practitioner? You mentioned a couple of sources for O1 steel, but have you noticed any significant difference in quality between ENCO for instance and your other sources?

Kind Regards . . . . ALlen

[Pedro Reyes]

...I should have said, the reason you anneal something is to relax / relieve the molecular stresses to make it tough, not to soften the steel. ...

You meant temper, not anneal, correct? anneal is beyond critical temperature (IIRC the terms) tempering is below. Speed of cooling is also an important difference. Just clarifying.

Pedro

[allen long]

Yeah, what you said . . .

Temper is the correct term .

I am not a metallurgist - my son is. That is what I get for trying to sound smarter than I am!

Many Kind Regards . . . Allen

You meant temper, not anneal, correct? anneal is beyond critical temperature (IIRC the terms) tempering is below. Speed of cooling is also an important difference. Just clarifying.

Pedro

[george wilson]

Everyone sells the same 01. They either offer English imported 01 or Starrett. Just hope they don't start selling Chinese made 01. That is happening in the industrial world. Machinists are ruining cutters when they run into a half melted ball bearing or other crap they leave in their metal. Their plywood is about the same too. Smashed soccer balls,pieces of fencing and other junk has been found in their plywood.

[Ryan Baker]

George, I find your comments about tempering in a toaster oven interesting (especially from someone with a proper tempering oven). My own experience with toaster oven tempering has been more problematic -- possibly due to my particular oven. I found that the heating coils produced local regions of much higher temperature within the oven -- i.e. there were inconsistent temperature gradients throughout the oven. Due to the size of the oven, some areas of the part are much closer to the heat coils, without enough space and/or diffusion to even out the temperature. I have taken parts out with clear color stripes across them right in line with the coils, and they got to much higher temperature than the average temp of the oven.

I usually prefer to temper with a torch. But for larger parts or ones where I want a very even temper, I have had better success using a full-size oven (maybe even convection!). A "real" thermometer does make a big difference though.

[george wilson]

I can't remember the book,as I left it at work when I retired in 2009. It was by a pro. heat treater. Odd name,Szumera,I think. CORRECTION: I just recalled the name: It is Jim Szumera. The book is "The Tool Steel Guide". I just ordered myself a new copy from Amazon for $21.85(or close). I am glad to have found this book again.A very useful and very informative book. I have other books,but this one is more concise and to the point. They used toaster ovens in professional heat treating shops. That's how I got turned on to it. A good thermometer is essential. You can look at something like a plane iron or knife blade,to see that the color is even all over. Move it around,or turn it end for end if needed. There is still skill and judgement involved.

It is a wonder how,back hundreds of years ago,they made beautifully fire blued sword blades,perfectly fire blued from end to end(these were fancy gentleman's swords I have seen). They did this in primitive brick ovens,and all was skill,no thermometer!!

They are VERY rare,but they also made hardened and tempered shotgun barrels in the 18th. C. that I am aware of. This was only on the highest grade guns,and was done to make the barrels more corrosion resistant. Now,I can tell you,evenly heat treating a LONG tube of very uneven thickness is a challenge. The thin end wants to get hot quicker that the breech. A VERY evenly controlled oven is necessary. I think it is a huge tribute to their skill that the old timers pulled that off. I have fire blued tapered pistol barrels in an oven myself(the brass mounted pistol I've posted here,for example). I can tell you,it is not easy to pull it off,even with a modern,pyrometer controlled electric furnace.

At work,where I had the money,I had 2 heat treating furnaces made for knife makers. They were 22"deep inside,electric. I have one at my home shop. We'd pre heat one of the furnaces to the tempering temp.,and use the other one for hardening. As soon as the part was quenched,and we could barely hold it for a few seconds,into the tempering furnace it went. That was an ideal setup. But,those furnaces are over $1,000.00,and I am lucky to have one. So,the toaster oven will do.

For smaller parts,I use the torch. They are easier to evenly heat with a torch.

[David Weaver]

I don't know how those guys knew what temperature they were tempering gentleman's swords, but I've seen harder temper japanese knife makers temper knives by heating them at the top of a forge and taking them out of the forge every so often and dropping water droplets on the blades to judge how hot they are by the action of the water droplets.

I use a kitchen oven to temper anything that I make that's not tiny, but I have a thermometer in it and I let whatever is in the oven temper for an hour. If the oven isn't preheated very long, I've noticed that on mine ( a ge convection oven) that the front is much cooler than the back, except for where the air circulates first in the oven. A good toaster oven would probably have a much more even heat (except maybe right at the window) and be up to temperature much faster.

[Roderick Gentry]

I find all of this kind of interesting and kind of weird. How can anyone recommend heat treatment for an unknown grade/chemistry of steel? The only way is to guess at what the steel grade is and what heat treatment is appropriate. The danger is that you may think that you have succeeded and then go to use the tool that you made and have it fracture and hurt someone.

The file example aside, there is virtually no risk of someone getting hurt. It probably helps not to pry the heck out of a mortise chisel if you can't tie a shoelace, and whipped the chisel up yourself. I normally just HT the end of planes and chisels. I am never going to get through an inch to 2 inches of material in several hundred planes and chisels. Even the old dudes who worked hard, died with shops full of nicely resalable tools. So if you don't even harden the material all the way (pretty typical approach for one reason or another) It can't snap.

At one point I made up a batch of plane blades and they turned out badly. The first I knew of it was that the edge hit a very hard knot and bent! I had been using the thing for about a year, and never noticed unusual wear or differences in sharpening (O1 blade in this case, but a goof is a goof). It was an interesting experience to see how effective even a goofed tool was, when it was not in one's brain that it had any problem. Some in the batch had skidded a file, so it seems as though they were coming out OK.

Even with the lathe tool example, in what universe today are people making thin sectioned scrapers, overhanging them a mile, then making heavy cuts. I just don't see how a small tool like that gets all over the shop if it was handled in any kind of competent manner. It won't be worth the trouble though, as the cost in abrasives to get it ground down, alone, is not worth the savings.

In the old days they used scrap approach to forging climbing gear (old meaning 1960s). Now there you might want to be sure you were getting axles or something.

As for spark testing, we used to do this a lot in the steel mill and only by very experienced people. Yes, you can kind of guess the carbon level but without actual training it all be a guess. It was so difficult for some of the grades of steel and not totally reliable that we went to portable spectroscopic equipment.

I agree with the posts that suggest that you buy a piece of steel that you know what it is and then proceed from that point.[/QUOTE]

[Gary Muto]

One way to improve the temperature profile in an oven (without a fan) is to make the surfaces as clean as possible. A lot of times the top of the oven goes unnoticed.