Questions about forging/heat-treating

[Dannyc]

Hello!

I'm kinda curious about these, as I plan to try my hand in making my own knife.

I've read somewhere that while heating up the steel, the gauge would be to make it hit up to non-magnetic. What does it mean by that? Where do I stick the magnet to find out? What happens if it's still magnetic, and the magnet sticks to it while it's glowing red hot?

Let's assume I don't have a thermometer to know the temp. of the forge.

Here in my country, where balisongs are being made (cottage industry), they don't have fancy thermometers or forges to begin with. Knife-making knowledge was handed down from generation to generation. By that, their only way of knowing when to stop heating the blade, is when "they strike the blade, and no sparks fly".. DUH??? I presume they're talking about the forging process, right? What does "sparks" have to do with knowing it's already the right temp to stop heating?

They consider the sparks as the "dirt" in the steel. (These are according to a friend of mine, who's been a long-time balisong maker)

Lastly, from what I've read (and learned, thanks) from reading the posts here, from steel bar to knife, one had to undergo the following: (please add any which I may have missed)

1.) Heat bar to non-magnetic
2.)Let it cool down without quenching it? (is this what they call annealing?)
3.)Shape the bar into a knife?
4.)Reheat it until non-magnetic again?
5.) Quench in water or oil
6.) Temper to 300c for 2 hrs per inch. ??

Did I miss anything? I really would like to learn about the proper procedure of this all.

Thanks, and sorry for asking too much stuff all in one post.

Regards,

Dan

 

[Osbourn]

That's quite a can of worms you want opened.
The first thing I'd address is the sparks. When you heat steel so hot that it sparks, you're burning out carbon. This is welding temperature, and much hotter than most of us forge at. I don't know about the balisong smiths, but I WANT carbon in my blades.
The way I go about making a knife, and I'm a beginner, so listen to any of these old hands advice over mine, is:
1: Select the steel according to what the blade will eventually do.
2: Cut to size.
3: Forge to shape. This is the complicated part that we always make sound simple. We heat the steel to make it ductile, then shape it with a hammer on an anvil, basically beating it into shape. When it's the shape we want, or close enough that we can grind it closer, that's when we do some of the next steps.
4: Normalizing. Not everyone does it, but I think it helps. Heat it up to critical temperature (Non-magnetic) and let it air cool. For some metals this will anneal, but most of the steels we work with, it's still too fast of a cooling.
5: Grinding. This can be done with anything as simple as a file or as complicated and expensive as one of those really cool belt grinders I've been drooling over. This takes it closer to the exact shape you want the blade to be when it's done.
6: Heat treating. Different for every steel, there are millions of words written on it on the net and in these forums.
7: Final grinding. I do a lot of polishing in this stage as well.
8: Final assembly. Another thing that sounds easy.
I know this will likely create more questions, but it's the framework that we all follow. I don't have a temp guage in my forge, I judge heat by eye, using what little experience I have, as well as my books.
Hope this helps!

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Oz

"Violence never settles anything."
Genghis Khan 1162-1227

Check out my egostistical homepage!
http://www.freespeech.org/oz/

 

[Ed Caffrey]

In between #4 & #5 above, put in the annealing step. Annealing for most forgable steels consists of heating to critical temp (non-magnetic), and cooling as slowly as possible. This refines grain structure within the steel, and makes the steel obtain it's softest possible state. Some things that can be used include, DRY lime, DRY wood ashes, DRY sand(not the best, but will do in a pinch), or my favorite.....vermiculite.
You spoke of "sparks"........if you see sparks, you have OVERHEATED the steel. This is carbon being burned out of the steel matrix. If this is allowed to happen, you will likely end up with a blob of stuff that looks like black cottage cheese on your anvil. As for the magnet. It is one of the most reliable ways to judge critical temp. Your eyes will lie to you (until you have a great deal of experience). I have magnets located on the side of the anvil, one resting just outside of the forge, and another at the quench tank. It may seem like a great deal to learn, but once you understand the processes, and their effects on the steel, it will become second nature.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com

 

[Osbourn]

Ed, where does one obtain vermiculite? When I've HAD to anneal, I've usually just left the blade in the forge with the openings blocked off until the forge cooled all the way, or put it in a powdered charcoal hotbox.

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Oz

"Violence never settles anything."
Genghis Khan 1162-1227

Check out my egostistical homepage!
http://www.freespeech.org/oz/

 

[gregj62]

You can get vermiculite a lot of places. Heck Wal-Mart carrys small bags, but the best place to get it is at your local garden surply place. That where I get mine.

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-Greg Johnson
ICQ#4236341