Wood Chipper Blade for a Knife?

M

mainemike

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Mar 28, 2014
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Good morning, recently I scavenged an old wood chipper blade. I did a little research and I have learned that it is made from A-8 Mod steel. Would I be wasting my time trying to use this steel to make a knife or other type of cutting tool? Should I anneal it first or just cut and grind it to the shape and thickness I want at its current hardness? Any input is appreciated.
 
Free steel is always good. I'm not a blacksmith or metallurgist but I would draw it back (anneal) first, cut, grind, heat treat and draw it back @400 deg before finishing. Show some pics if you make a knife. :)
 
A8 Mod is imho, a fine steel for making knives. If you have an oven or otber good temperature control, you can anneal, shape and treat it. If not, grinding as is isnt out of the question, but will be slow, so as not to over heat it. It's an air hardening steel, with all the complications associated with the higher alloy content of those steels.
 
I have access to a metal band saw and torches. I also have a small furnace. I am going to experiment.
 
Mike,
If you know enough about working with high alloy steel...and have the equipment to do that work......using the A-8M steel would work ( if it actually is A-8M). But, from the fact that you asked, I can be pretty sure you should not attempt it. You would be far better to get a bar of 1075/1080/1084.

Marksharp - before giving the advise on how this new person should use this "found" steel it might be best to stop and think - How should he anneal it? How should he HT it?
I would be interested in your answers to those questions. How many A8 knives have you made from scratch using the methods you gave?
 
M means "modified". What the modification to the alloy is anyone's guess without an analysis on this particular piece. Most M steels are modified to increase some attribute like toughness. The HT is usually pretty much the same. A8 is only .50-.60% carbon, so lets hope it has extra carbon as the M. IIRC, it is also pretty high in silicon. For an industrial drop forge punch it is probably great...for a knife maybe not so great. I would pick many other steels before using A8, but who am I to tell people how to waste their time :) .
 
That's going to take high temperatures with good control to get soft enough to work very easily. And then a likewise quality heat source to harden correctly.
I'd follow Stacy's advice and spend the $10 or so to get a chunk of 1084 or something to play with. Air hardening steel for your first knife, already hard, will make you want to quit.
 
Markesharp said:
Free steel is always good. I'm not a blacksmith or metallurgist but I would draw it back (anneal) first, cut, grind, heat treat and draw it back @400 deg before finishing. Show some pics if you make a knife. :)
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I am going to disagree with you about that. Free steel almost always costs you more in the end, than if you would have just bought quality steel in the first place. I'm relatively new in knife making myself and I too started out thinking free scrap was good. I am not nearly as versed as Stacy or Salem, but I can tell you even with my limited experience, the blades I've made from scrap steel cost me at least twice as much as the ones where I bought the steel. When you start factoring in extra time spent, it really adds up in a hurry. Then to top it all off, you know exactly how to heat treat for optimum results.

Good luck,
Chris
 
Salolan said:
I am going to disagree with you about that. Free steel almost always costs you more in the end, than if you would have just bought quality steel in the first place. I'm relatively new in knife making myself and I too started out thinking free scrap was good. I am not nearly as versed as Stacy or Salem, but I can tell you even with my limited experience, the blades I've made from scrap steel cost me at least twice as much as the ones where I bought the steel. When you start factoring in extra time spent, it really adds up in a hurry. Then to top it all off, you know exactly how to heat treat for optimum results.

Good luck,
Chris
Click to expand...

+1 and I will add that when you have the skills to evaluate and work with found steel, you will have educated yourself as to why it is a waste of time to do so. Wood chipper blades are much like lawn mower blades. Designed and manufactured to bend, not chip when they encounter a hard object. As such they are typically steel with .50 or so carbon content and HT to a low RC. Like Stacy said, the M is anyone's guess, but I am going to venture that it wasn't to add carbon....

Sentimental steel is my only caveat to that. If this is a blade from the wood chipper that took Uncle Carl's arm, have at it. Otherwise use it for some project that calls for a non-critical bar of steel, or save it up and scrap it.


-Eric
 
Just to elaborate a bit more, you don't anneal air hardening high alloy steels like you do simple carbon steel. Most attempts without a HT oven end up making it hard...not soft.
 
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