Unknown steel.


Well-Known Member
A long time ago I was given a diamond concrete circular saw blade like what they use for road construction. I have someone wanting me to make them a two handed machete but I can't find a one piece of still long enough to cut it out of I was going to use that big blade but I don't know what kind of Steel it is can anyone give me maybe an idea of what it is or just a general heat treating guide to go by for it.

C Craft

Well-Known Member
Back in the day most blades were made of carbon steel. The same tooth the steel was made from was part of that same steel. That is why you could sharpen them over and over if you didn't get them hot!

Nowadays if the blade has carbide teeth on it chances are that inner part of the blade is made of not much. It is usually a conglomeration of steels that is designed more to keep it from heating, and warping. You can do a spark test to see if it may have enough carbon to harden.
Take a look at this link and it describes and shows what the result would be if it is sparked on a grinder!


My understanding is that those blades are not hardenable. You could cut a small piece, heat it to nonmagnetic, then quench and see if it will break easily. If it does, it will then take a lot of testing to see what temperature to quench at, whether it needs a soak at that temperature, what oil to quench in, and what temperature to temper at.

I started out using old buzz saw blades. Once I figured everything out on the first blade, the second one was different. From here, I decided it wasn't worth it to me to use unknown steel, a decision each maker has to make for themselves. Unknown steel can make great knives if someone wants to put in the time to work with it and figure out how to get the most out of it.


Forum Owner - Moderator
SOMETIMES those type of blade are made of 4140, but that's the problem with "recycled" stuff for Bladesmithing/Knifemaking..... you just never know. What makes it even more maddening for a Bladesmith/Knifemaker is that the same item/part number, from the same company, is very often made of a different steel type from run to run. This is called "Spec Manufacturing"...... where as at one point in time, the exact steel type an item was to be made from, was the first annotation on an order, that's no longer the case. It all has to do with profit.... even saving a few pennies on the production of an item adds up to more profit for a company when you consider thousands and thousands of the item are produced. These days, with "spec manufacturing", the functional requirements, for a given amount of time, or repetitions of use are the driving factor(s), and an annotation of "use the least expensive material that will meet the requirements at the time of production" are how the decision is made as to what steel type is utilized. This means that all the old literature that many Bladesmiths/Blacksmiths still refer to concerning certain items being made of specific steel types is totally useless.

If you stick with Bladesmithing/Knifemaking long enough, you will find yourself wondering about all those blades you made from "recycled" items, and waiting for one to come back and bite you.


Dealer - Purveyor
buy known steel from a good shop. that said, there is a big market for stuff made from junk steel. knives made from old nails, old railroad spikes, pieces of railroad track seem to be good sellers to people who have money and no idea what a good knife is.


Well-Known Member
ok thanks. well I need a big piece of known steel then because from the information I gathered this isn't going to be worth my time and effort. so I'm need about a minimum width of 6 inches and a minimum length of about 24" anyone know where I can get that?