tempering

[Frank Novak]

After a blade has been quenched, should the blade be tempered asap or does it matter if it is done lets say a couple of hours later.Thanks.

[Lin Rhea]

It's best to go ahead and draw the temper as soon as possible. A fellow maker told me he hardened a blade and stopped for lunch within hearing of the blade and heard a "tink" and sure enough he checked and it had cracked.

It might take a week or it might take minutes.

[Ray Hammond]

I had that happen as well....I'm so clumsy, and have sometimers disease too...so I always make sure I have time to draw them back right away so I don't FORGET....

Cause once I "thought" I'd drawn one back and took to whacking on antler....some nice big chunks came out of that one very quickly.

Also knocked one off the table once....broke in two like shattered glass.

[ed cowden]

I am no expert but I was a machinist and have heat treated a few pieces of steel. The heat treat books and the machinery handbook all stress tempering as soon as cooled and I would stress over just taking time to knock the bark off so I could see the steel color. We would always have the tempering oven set a temperature so it would go right in. I guess you guy's go back to the forge a watch color.

[gudspelr]

I've also heard from friends that had BAD experiences with waiting to temper, so I've never waited. I make sure to have the oven at temp so I can run the knives through at least once. There have been times where I haven't had the time to do 2 or 3 cycles, but I always be sure I get at least one. Then I write down what I've done and can run them for more tempering cycles the following day or whenever.

I've broken several blades to look at the inside for various reasons, but those were pretty well in my terms. It's just too painful to me to have it broken after the work into it by leaving it in such a stressed state or forgetting I didn't do any tempering and  go to testing... I think I have that "sometimers disease", too   .

Jeremy

[kbaknife]

Originally posted by ed cowden:
 I guess you guy's go back to the forge and watch color.

I don't know of anyone here who tempers in their forge.

[Lin Rhea]

Ed, What you may be thinking of is the way blacksmiths are often remembered as tempering. They would heat to quenching temperature, quench the piece leaving it in the oil just long enough to convert the steel to martensitic, then remove it to allow the heat to travel and draw the hardened edge. More or less in one heat.

There is a good description of this process in Foxfire 5 under the blacksmith section by a Mr. Zeller (sp)hardening a cold chisel. They would use the color of the surface oxides as an indicator of just when to quench it (2nd time)to stop the colors from continuing to run. This is still done by historic blacksmiths.

Knife blades are not usually done this way due to the complex geometries. An oven is much better.

[ed cowden]

You are correct Lin. I had to make a chisel in apprenticeship class and that is the way we did it. Also the Foxfire books were just getting started when I was in the Navy. One of the young sailors said his High School ( in NC I think )started it to get their students to talk to and record some of the old ways of doing things before they were lost to their families. The old Blacksmith in my hometown was still in business up until I was about 16. He made many things for the farms around there and it was fascinating to watch him work steel in the forge and anvil. I know that knife making is more scientific and the heat treating part maybe be one of the most complicated to learn and most important. Thanks for the info.