Grinding Hardened Steel

M

me2

Joined
Oct 11, 2003
Messages
5,091
Now I know why most people grind their blades THEN harden them. I've gone though 3, 40 grit ZrO belts and some time on a bench grinder trying to shape my current knife project. The bevel is about 3/4" wide, chisel ground on an old file, about 1/8" thick, and when trying to get it down to 1/32" before polishing, it took forever. I was going to make it without a secondary edge bevel, but I dont think I'll live long enough. I dont have a way to reharden a blade this big, which is why I'm grinding a hardened file. Am I doing something wrong, or should it take such a long time to grind this bevel? The benchgrinder was pretty easy grinding. The belt sander (1x30) may just be way under powered, but it works for soft steel, so I figured I'd give it a try.
 
You have to anneal it first,otherwise its gonna be way too hard to grind.After that much grinding on a hardened peice of steel your gonna want to re heat treat and temper it anyway.The 1X30 is going to be an exercise in frustration.save up for a good belt grinder or build one.The recources here are endless.
 
Man, I'm not doing that again. Okay, maybe, one more time, since the file is already ground down for a stick tang and the blade is thinner and narrower. Finally finished the blade, a sheepsfoot blade. No detectable loss of hardness, as I cut those parts off that changed color, and ground the whole thing bare handed so I could feel any heat buildup. It tested out at 64 HRc on the machine at work, so hopefully I havent lost any. Now to put a handle on it and send it to the owner. One thing I did different is it is not a chisel ground edge. Only the primary grind is chisel ground. The edge bevel is a normal "v" edge. Gotta test it tonight on some cardboard before sending it.
 
I usaully heat treat after grinding, but sometimes that's not practical. (Can't imagine grinding a blade on a 1x30).

64 RC ??? Hope the blade isn't too long. Makes me kind of nervous.
 
I've said it a lot of times, every grinder has it's place. The 1X30 wouldn't be my first choice for hogging hardened steel. For one thing, it's too fast. If you get past 1/16" and don't turn up a blue spot, your good.

OTOH I have one that I use exclusively for my final convex edge and would feel lost without it.
 
If you haven't already handled it, you need to temper it back in your oven. If you will run three one hour tempers at about 450o, you should get a rockwell of around 57, to 59, but be sure to use an oven thermometer. Never trust your oven setting, most are wrong. If you want it harder, run it around 430o, but you definately need to temper it.
 
im really new at this and I have done a few files but I had to use the hand grinder first then put it on the belt. but thats just because I cant afford a good belt grinder but it seems to be faster.
 
The bench grinder I used was at the shop where I worked. I changed jobs so I dont have access to it now. The belt grinder works ok for small areas, but the 3/4" by 3.5" bevel I was working for the grind was just too much I guess.

The hardenss is right where I wanted it. I wanted to try a very hard blade after reading some posts on rec.knives. Its an experiment more than anything. I will say its pretty tough where it is. I cut the tip using a dremel and a cutoff wheel. After cutting halfway through, I tried to break the piece off with a claw hammer, but couldnt break it. I had to cut about 85% of the way through, and then it took 3-4 good whacks to break it. I can harden smaller blades, but this one is thicker and not as finely ground, so its got more mass to heat up.
 
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