The Two Commandments of Heat Treating

me2 said:
There is something to be said for not getting ahead of ones self.
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True, and newbies should especially pay close attention to that.

There are no short cuts and getting our priorities straight, right from the get go,... is good sound advice.

... Beyond a knife performing the way it was intended to, AND withstanding the test of time… it all becomes foggy and uncertain.
 
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I think that's the eigth one, Calvin. But, none the less it's a good one.


How about for #3.,... Never believe "Rockwell hardness" is the only thing.
 
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me2 said:
Know thy steel.
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I think me2 has named what should be Number #1

If you don't know what you are dealing with? all of the rest of this really doesn't mean much.

I use to take unknown steels and do the spark testing and then the file test before & after HT to listen for improvement. These day's I start with a known steel from a Mill or supplier I trust.

So Tai? What does our resident Crackologist have to say? LOL.

Laurence

www.rhinoknives.com
 
#5 Honor thy fire and thy quenching medium.

#6. Do not covet thy neighbor's salt pot.

#7. Thou shalt not burn thy steel.

#8. Always test for hardness.
 
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Good enough. :)

I'd just like to add that, many of the common problems like warping (distortion) and cracking can be avoided, minimized and/or corrected simply by realizing that heat treating knife blades is a specialization. All the same rules apply, but knife blades present special problems, mostly due to their shape and/or geometry,... generally, long and thin, pointy with wedged (triangular) or diamond shaped cross sections. Not all knife blades are exactly the same, but this basic configuration makes them extremely problematic. The idea that knife blades are "simple" is just not correct and special allowances and considerations are necessary to help compensate for these very basic areas of concern... simple to understand, but not so simple to excel.

That’s as “simple” as I can make it.
 
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One said:
Two general rules that come up time and time again in industrial heat treating discussions, are:

#1. The end use application of a part or component dictates it's heat treatment.

#2. Use the slowest possible quenching medium necessary to achieve the desired structures and/or properties.

well you missed em good buddy as far as industrial production goes.
1) heat treatment must be performed as quickly as possible using least expensive equipment available. said equipment must be capable of running 24-7 for a minimum of 180 days without maintenance. heat treat quality is not judged by hardness or other tests, but by number of returned parts we can't blame on our suppliers or customers.
2) quench media must be inexpensive, non-harzardous(if you can't pour it down the toilet, we can't use it), non-staining, leave no residue, and have a low enough evaporation rate that the tank only has to be filled every 180 days
3) in our advertising, there will be no mention hardness numbers or chirpy tests or ....... use instead: adequate, functional, easy to maintain, meets all standards, and any other adjectives that are soft, fuzzy, and impossible to disprove in a court of law.

just observations of what i have seen in 40 years of maintaining equipment for the military and manufacturing firms.

scott
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One said:
Good enough. :)

I'd just like to add that, many of the common problems like warping (distortion) and cracking can be avoided, minimized and/or corrected simply by realizing that heat treating knife blades is a specialization. All the same rules apply, but knife blades present special problems, mostly due to their shape and/or geometry,... generally, long and thin, pointy with wedged (triangular) or diamond shaped cross sections. Not all knife blades are exactly the same, but this basic configuration makes them extremely problematic. The idea that knife blades are "simple" is just not correct and special allowances and considerations are necessary to help compensate for these very basic areas of concern... simple to understand, but not so simple to excel.

That’s as “simple” as I can make it.
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This is kinda all over the place. First you state that there are problems that can be avoided by just "realizing" that there are problems, which is a silly standpoint. You need to know the exact problem that you need the solution for and then work towards the solution, ever being careful that you don't waste time and solve "problems" that have already been solved. As far as industrial heat treating a knife blade is about as simple as it gets.
If the steel you're using needs s faster quench than you have, or can afford, use a different steel, it's that simple. "industry" would do exactly the same. If you find that your steel has inclusions or other problems, contact the supplier or switch suppliers, bad batches of steel can and do happen, "industry" knows this as well. Why work with bad steel if you don't have to.

Heat the steel to austinizing temp, hold for the required time, quench in the proper medium, temper at the desired temp for the end use. There is not a problem with testing rockwell hardness, while an exact RC number may not be the end all of knife design, knowing what the numbers are along the process will let you know if there was a problem with your heat treat, A hardness tester is on my short list of tools to buy, as it really is the only reliable feed back you have in the process.

Zeb
 
The article I posted the link to explains the specifics of it. That's why I posted it.

Yes, there are ways to work around many of the problems associated with heat treating knife blades, but first one needs to understand what the problems are.
 
I wouldn't call knives a complicated shape. Triangles are about as simple a cross section as you can get, next to round rods and rectangles. They are more complicated than these, but much more complicated stuff gets successfully treated all the time. Gears, splines, bolts, threaded rods, dies, etc. are what I'd call "crack prone" and "complicated". Some consideration must be given to things like the tang shoulders, plunge cuts, etc., but these are issues I've seen addressed in every knife making how to I've read. People do some odd things sometimes to make knives more complicated, like brazing on guards before HT, but realistically, people can screw anything up.
 
Again, I'll just refer back to the article.

Although a triangle is not a complicated shape in and of itself, it presents problems in heat treating and it's much different than a circle or rectangle. So, it's not just how simple or complicated a shape is, but the nature of the shape and how it effects heat treating. This concept really shouldn’t be that difficult to understand.

So, that being said, I see no need to keep repeating myself, or to quote the whole article word for word one sentence or paragraph at a time.
 
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Different shapes respond differently to heat treating.

We could pick at the article, because it covers a lot of ground in very few words,... but I think the main points and basic principals are solid and very well established. It does reference knife/sword blades in a couple places, but was not written specifically just for knifemakers.

... but, first we'd have to read it.

How any or all of it pertains to knifemaking is really the most important and/or potentially productive part in this context.
 
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