The secrets of heat treatment

golok

golok

Joined
Oct 20, 2000
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Occasionally, I am intrigued by what is left unsaid about heat treatment of knives. It is an open secret that durability of the keen edge of a blade is largely dependent on heat treatment.

I don't know whether it is a closely guarded secret but knifemakers generally don't elaborate too much about their own methods of heat treatment.

One of the best performers in this particular field is apparently Paul Bos. From what I understand, a lot of knifemakers send their knives to him.

Some knifemakers of course heat treat their own knives.

Is it a difficult process to learn? There are numerous types of metals in the industry. I reckon it all boils down to knowledge and vast experience.

Proper heat treatment equals a sharp edge that lasts longer, am I right?
 
Golok:
Moving to Shoptalk.Those dudes over there are the ones to ask.
 
Golok, your assertion that the heat treatment is of primary importance in any blade is correct. However, with regards to makers and their willingness to share their methods, I have actually found them to be very forthcoming. Ed Fowler and Ed Caffrey in particular have written extensively via book and web site regarding the heat treatments of their superior blades. There are a number of other makers who have also written extensively on the subject. Paul Bos has posted his "recipes" here on at least a couple of occasions.

Proper heat treatment of stainless steel can be demanding due to the equipment needs and timing factors. That is Paul Bos' forte. Heat treatment of carbon steels can be mastered by almost any smith using his/her own tools and shop equipment, as long as they have the mind set to experiment with the steels they choose to use. The equipment for heat treating carbon steels costs substantially less, but in my view, the learning curve is probably the same as for stainless if the maker is willing to invest the time required to perfect his thermal treatments.

Heat treatments are not hard to learn. However, the maker must constantly experiment to ensure that that the end product is of a consistent high quality. What you learn as time goes on is that each batch of steel can be different as well, introducing variables that can change what the maker long believed was a "tried and true" heat treatment methodology. Ed Fowler has written extensively about his search for consistency in 52100, his steel of choice.

Keep an eye on this forum. I think you will see fairly regular posts regarding thermal treatments and a regular sharing of "recipes" among makers.
 
Just do a search in the shop talk forum and you will have more posts on the various aspects of heat treatment than you can read in an evening.
 
I'd say Fox gave about a perfect general description here, and then just browse the threads her ein Shop talk. heat treating(and grinders and how to build them) are probalby too most talked about topics in here. Well, that and showing off work when it's finished. :)

Heat treating is black magic I've learned, and Fox is very right that different batches treat differently. That's why when I start doing this a lot more will probably buy 20ft at a time minimum. gives you enough steel to work up a good consistent heat treat to use for a while before you have to get more steel and test your heat treating again.

But the HT does make the blade(well, HT and temper) and everyone has different opinions, and every method has different advantages and disadvantages.
 
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