Differential Tempering

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pastormarty

Joined
Mar 22, 2010
Messages
157
Can somebody tell me if Beckers are differentially tempered and what does that mean? From what little I've heard it sounds like the edge is harder but that you loose edge holding over the years as you sharpen through that edge. Is that correct?
 
pastormarty,

I think you are mixing your terminology.
Differential hardening/tempering is when certain areas of the pattern shape are hardened to different hardnesses; ie. spine of the blade versus the cutting edge or tang versus the blade.
What you are describing on the edge is a term called hardenability. Which is the ability of the particular steel to completely harden through the entire cross section of a steel object.
As for Beckers; They are differentially hardened. The blade is fully hardened and the tangs are spring hard at the junction of the blade and tang, while the pommel end is softest.
Hardenability is determined by a lot of factors but 1095 CV has very good hardenability and you should not see much if any drop off of hardness as you sharpen the edge.
Hope this helps.

Best Regards,

Paul Tsujimoto
Sr Eng
Prod Dev and Qual
KA-BAR Knives
 
Thanks Toooj. So can I infer that the blade gets harder moving from tang to tip? How is differential hardening accomplished? Heat or work?
 
pastormarty,

The entire blade of the knife is hardened (tempered to 57-59HRc). The shoulder (junction of the blade and tang) is slightly softer(HRc 48-52) and the hardness decreases as it moves toward the pommel end (HRc 20-30)
This can be accomplished by several methods but at KA-BAR, we use salt pots. The blades are hung vertically from racks and the entire blade is put into the molten salt. The tang is left out of the salt but the heat creeps up the tang partially hardening the shoulder area. The pommel end is entirely out of the pot so it is never hardened. Any hardness in this area is the result of work hardening from rolling.
Hope this helps.

Best Regards,

Paul Tsujimoto
Sr Eng
Prod Dev and Qual
KA-BAR Knives
 
That sounds really cool. I was an engineer before seminary, so I still find this stuff interesting. Thanks again for taking the time to explain it.
 
pastormarty,

You are very welcome.

Clich,

I'm thinking you should be able to see some salt bath heat treating on you tube or on the web.
It's an old technology that is still very relevent...to KA-BAR, Becker and JAB at least.

B. Mauser,

That is our stainless steel HT oven. Not the same type of HT, but still a very impressive piece of equipment.

Best Regards,

Paul Tsujimoto
Sr Eng
Prod Dev and Qual
KA-BAR Knives
 
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