What's the best method? What's your opinion?

A

anduin-de-smitty

Joined
Sep 30, 1999
Messages
18
this has to do with the best method of heat treating your blade. usually i fully anneal my blades first (like i hope most people do) then i heat it up for hardening but i only quench the cutting edge, leaving the spine quazi annealed. i then quickly stick it in the oven and temper accordingly. (i usually temper twice)

some people like to quench the entire blade for hardening, then they temper the entire thing, and after that they selectively temper just the spine of the blade, leaving it softer than the cutting edge.

i was wondering, which method do you think is better? what do you do? which would be better for knife flexibility?

would the full blade quench and selective temper offer more spring-like qualities in the spine of the blade, when the selectively hardened blade with the annealed spine would leave the blade prone to bending and staying bent under stress? would the fully hardened knife spring back?

ok, you can see i'm a little confused, i would really appreciate everyones help.
thankyou for your time
- Loren Patterson
 
Loren,
Welcome! You will be able to get more great heat treating advice here that you can imagine!! BUT.........can you tell us what steels you are using?
As a stock removal maker, I treat the entire blade including Cryo. I feel that a sequential process should at least harden part of the tang to prevent bending at the guard are. This is just my opinion
smile.gif

Neil

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Blackwood Knives
Talonite knives in stock!!
http://www.geocities.com/Eureka/Meeting/5520/index.html

[This message has been edited by Dr.Lathe (edited 04-08-2000).]
 
It depends on the steel you are using! I do the edge quench on carbon, L-6 and 5160 or 1095. This is not practical on stainless steel IMHO. I also think depth of the edge quench is a contributing factor. For small hunters or skinners 4in. or under I like half the blade to be quenched, bigger knives camps or bowies I prefer a third of the width of the blade. I don't quench the tang, I worried about bending in that area too, but have not experienced that problem. I am now experimenting with doing three normalizing heats before quenching and skipping the anneal before hardening, in a search for developeing finer grain. I have read,( no experience with this steel) that heat treating blades of O-1 that it is better to quench the entire blade and then do a soft back draw, I don't remember where I read this, but the author stated that this steel responded better to this treatment than it did to the edge quench method.

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If winners never quit and quitters never win. What fool said quit while you're ahead?
 
I have been forging 10" long blades for my journeyman test for ABS using 5160. I forged them out with a distal taper from the gaurd to the tip. About 1/4" thick at the guard. I heated the entire blade in the propane forge at 1500-1600 (non magnetic) and quenched it in 125 degree texaco hydraulic oil. Only about 1/3 of the edge was quenched. I used alot of oil but spaced the blade up from the bottom of the tank with thick iron so only 1/3 of the blade got wet. I think it is important to use as much oil as you can to wick away the heat. I tempered at 350 Degrees 2 times at 1 hour each soon after hardening. The blade will pass the ABS test. (cutting 2x4 in half twice and still shave hair plus bent in a vice to 90 degrees without breaking) It wont spring back to true though. But will straighten back for more punishment. Bruce
 
Bruce, how much bend angle does your blade retain? I forgot, there is another method used for the differential quench, and that is the clay coating method to prevent more heat from going into the back of the blade, I bought a can of furnace cement to give it a try, but haven,t gotten that done yet.

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There is no shame in being wrong...only in failing to correct your mistakes.
 
i'm a hard believer of 5160.. i recently made a bowie knife with an overall 20" and a 13" blade, it wouldnt fit in my forge (length wise) so it was difficult to do.. i heated the whole thing and quenched the edge, and i did it one more time. i then tempered in the oven at 475 degrees (which to my suprised turned it blue, i was hoping for brown) and then i did it again at 375.

the only other thing ive worked with is L-6 and some files.

another question i have is why every tempering chart i see is different. for instance.. "A blacksmithing primer" light straw is said to be 428 degrees, "edge of the anvil" light straw is 300 degrees.

when i would temper my 5160 knives at 375, they would be medium straw.. but when i turned it up to 475 it came out blue, 475 is supposed to be straw in "blacksmithing primer", and brown in "edge of the anvil"
confusing eh?

does everyone think light-medium straw is a good color for most smaller knives? what do you usually use?

and back to my origional question.. lets say i had two identically make 5160 knives (its impossible to make them exactly identical, but for scientific purposes, lets pretend they are) and one is fully hardened and selectively tempered, the other is selectively hardened (only the edge) and is tempered as usual, which is more likely to bend without breaking, and which is more likely to spring back to strait?

thankyou for your help
- Loren
 
I think a blade made from 5160 can be tempered to be a spring with a blade edge. They use this steel for car springs. I have never done it but read that if you temper the hardened blade in melted lead like they do for black powder gun flintlock springs it will temper back to spring temper. Im not sure what that temp is but its hotter than the edge temper. I would try tempering the whole blade at spring temper and reharden just the edge with a torch and quench. Then temper the whole blade at 350-375 for edge temper. The back would be a spring and the edge would cut good, the center is bound to lose some springyness but will bend both ways.Let me know what you think, Bruce
 
Oh, about the light straw color, My 5160 blades never did turn yellowish even up to a 400 {too soft} temper. They stayed pretty silver. The 52100 blades always turn a nice light straw. Bruce
 
I have found that different types of steel will be different colors at different temps. 5160 will not be the same color as L-6 at 400f. Testing,testing ,testing and test when you get a new batch of steel. I have heard that lead fumes are detrimental to ones health, isn't the same thing accomplished in molten salts. Some blademakers like them a lot forrepeatability and consistancy. Springmakers also temper in saltbaths. Blue is good for springs but may not hold an edge as long as you would like. Test it and find out.

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There is no shame in being wrong...only in failing to correct your mistakes.
 
Unhardened steel is not recommended. Relaxing (annealing) the metal before heat treat is fine but not always necessary. The goal of heat treating is to control the grain size and allotrophy (molecular phase change like cooking an egg that starts liquid and becomes solid because of the heat). Unhardened metal in the blade is ismply like the runny white of a half-cooked egg. Harden all metals completely. Tempering controls the grain growth. I leave it harder on the edge (small, tight grains) and softer at the spine and tang (long slip grains) for flexibility.
I suggest finding a book on heat treating to help you while you learn more about this.
If you want flexibility, fully harden and temper to spring hardness desired. Unhardened blade steel is not flexible. It is soft. It is the hardening that gives the metal it's "memory" and the tempering gives it the flexibility.
I have a lot of links available for web sites that offer tech help and info. If you're interested e-mail me and I'll send them to you.

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Gene Osborn
Center Cross Metal Works
For the word of God is living and active. Sharper than any double-edged sword...
Hewbrews 4:12
 
Gene,I have seen several posts recently on www.swordforum.com that suggest normalizing before quenching multi normalizing for 5160 and 52100 may be beneficial. There is a recent post from a swordmaker that uses the stock removal method, he said that his twists and warps have been greatly reduced by a normalizing heat before quench. I'm experimenting with a triple normalize at 1100 to 1175f, before quench. Wouldn't the grinding after forging also induce stress to the steel? When I used to heat treat pressure vessels the soak for 1 1/4 chrome was 1175 to 1200f. This was to normalize the vessel after welding.

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It is better to bear the rebuke of a wise man than to enjoy the flattery of fools.
 
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