What you need to make a knife

[hyfan]

Shing, I have read your account on heat treatment and I have a question to ask regarding the desired oil temperature used when hardening.I personally heat the oil for both 01 and 5160 when hardening.To the best of my knowledge the oil has to be heated for two reasons.The crystaline structure is determined by the rate of cooling during the quench. Cold oil will cool the heated blade faster than a slightly heated oil, hence the crystaline structure will be determined by the rate of cooling. This may have effect on the final performance of the blade.Secondly the oil is less viscous at temperature and the oil immediately around the blade during quench is is less likely to cavitate.This will provde a more efficient heat release from the blade into the oil.
Can we discuss this further?
Regards Hyfan
P.S. I found this link on bcuk it goes some way to add the 'what you might need to know' to the 'what do you need to make knives'-Im the first to admit that there is a need to understand the metallergy to make better knives-see the following I think its a great article http://swordforum.com/metallurgy/ites.html
Cheers

 

[Shing]

Quenching oil is one of those subjects that is often debated in knifemaking forums. My test for a blade that is properly hardened is to see if a file can cut into it after quenching. A properly hard blade will be harder than the file after queching and the file would slide off the blade. I test the whole length of the blade edge to make sure there are no soft spots.

The type of oil and its temperature does have an effect on the hardness of the steel and its structure but to what extent is the subject of many debates. There are fast, medium and slow oils. Animal fat is fast and veg oil is slow. Synthetic oils can be formulated to be fast, medium and slow. A fast oil is good for making hard blades or blades made with steels that should be water quenched.

Warm oil cools blades faster because its less viscous and allows better cooling by convection. Commercial heat treaters use circulating quenching tanks to make sure work pieces are cooled uniformly and minimise cavitation.

I have always used veg oil and have not had any problems with it. Its a slow oil and I like it because it minimises the risk of cracking while giving a blade that is very hard. I'm sure others have used a variety of oils with equal success.