Hardening and tempering advice

[mmcniven]

Hi

I am making my first knife at the moment i have cut out and shaped 2 pieces fo 01 steel and am ready to harden and temper the blades. I have been reading David Boye`s book Step-by-step knife making and he recommends hardening tempering and then annealing the back of the blade while keeping the hardness only in the cutting edge. Is this recommended for a knife which will be used for bushcraft ? will it effect the use of a fire steel on the back of the knife. I have a few knifes i use for bushcraft and they appear to be vey hard on the entire blade and dont appear to have been annealed. Any advice would be appreciated.

Michael

 

[C_Claycomb]

Making the back of the blade soft is more important when the knife is going to be used for chopping, when it is going to have to withstand impact. For something the size of the Woodlore knife, about an inch deep, that is going to be for cutting and carving only, I wouldn't really worry about it.

When I have treated blades I have gone with an edge quench rather than trying to draw the spine back to a lower hardness. The edge quench can still be done on smaller blades where-as using a torch to heat the spine can get fiddly. Wayne Goddard's books are great for heat treating info and general knife making on a budget.

Even a spring temper spine will be hard enough to scrape sparks, just not as well as it would if harder. In practice it probably won't make a noticable difference on a small blade.

What sort of set up have you got for heating the blades?

Good luck! Make sure you tell us how it works out!!

Chris

PS. The debate on edge quench, full quench and draw the spine, or plane full quench is one that can get some makers really riled :roll: Everyone seems to have their own ideas

 

[mmcniven]

Thanks for the info

To heat the blade i am using an oxy-hydrogen flame run through an atomiser with either MEK or meths which gives a flame temperature of between 1200 and 2300 depending on the atomiser fluid used to heat the blade and probably an oven to temper.

Can i ask how you edge quench as opposed to fully quench? I take it this is done in the hardening stage. What type of oil would you recommend for quenching ? i have heard that some makers use olive oil.

Michael

 

[C_Claycomb]

Wow. :shock: That sounds a pretty high tech heating arrangement!! And here I am using a B&Q propane/butane plumber's torch :-?

Yeah, edge quench is for hardening. Surprise surprise, you initially just quench the edge :-D I have a large baking tray as a quench tank. I put a plate of pre-heated steel in there to help keep it warm and act as a depth regulator so I can put more oil in the tray. I set it up so that when rocked edge down against the steel plate, about 1/3 to 1/2 the blade is submerged. I rock the blade back and forth till the colour is out then fully submerge it in the deeper oil to the side of the plate. Seems to work.

Oil wise I cheat, I lifted about 6litres of castrol quenching oil before my works heat treat dept closed down. I have heard that peanut oil will do, and olive oil, old crank oil, lots of things. Even used heat treat oil that has passed its comercial use limit. There are bound to be discussions on the Custom Knife Forum or on Shop Talk at BladeForums.

 

[mmcniven]

It sounds falsh doesnt it, i am lucky to have a friend who is a jeweller so i can get access to all his kit.

Thanks for the information on edge quenching i will give it a go and send you some piccies of the finished knife.

Many thanks

Michael

 

[Martyn]

I can honestly see no practical benefit from differentially hardening or tempering a small blade. For a sword, parang or golok, then for sure, it's a must. But for a small (read under 6") and relatively thick blade, why do it? Just harden and temper the whole blade. If the whole thing, spine to edge is 58RC, then what's the problem? Unless you are planning to put the blade under lots of lateral tension (ie use it as a pry-bar), then the risk of it snapping would be none-existant.

As far as I can see, the only reason for a differential heat treat on a small blade, is for cosmetic purposes.

BTW, the Alan Wood/Ray Mears woodlore knife, is not differentially heat treated. It seems to work OK -