HELP.....What did I do wrong??? Update: I got it right!!!

Justin King said:
I would clean the blade to shiny steel, then heat a larger/thicker piece of steel and draw the spine of the blade along it until the colors start to creep towards the edge, and quench in water or oil when the brown starts to reach the edge, or when the purple is 1/2" to 1/4" away from it. Do this as evenly as possible and leave the very tip until the end or you will over-heat it. I would repeat this 2 or 3 times.
You can heat the blade directly with your torch but the risk of over-tempering it is high and likelihood of getting any consitency is low.
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OK, you and Canid are saying the same thing with the heating of the larger piece of steel.......best I've got lying around is some old leaf spring...

I didnt realize that you quench during tempering though. Are you saying once the brown creeps down to the edge, I should quench in water or oil until room temp then repeat 2-3 times?
 
You can use the OA torch. Using a small flame, gently heat the thicker portions of the blade. Keep the torch moving at all times, so the blade heats evenly. First, the blade will turn a straw color, then purple, then blue. You want it straw to purple. Try to heat the thicker parts to straw and keep the heat even, but if you have to get the thicker parts purple, that's OK. The steel must be cleaned or sanded to bare metal first. Keep the torch moving, and stay away from the thin areas. Practice on some scrap metal first.
 
Yes on the last, cycle down to room temp and repeat. The quench is specific to this type of tempering, to keep the edge from over-heating. With this method you are doing a differential temper where the spine is being heated hotter than the edge and will be softer and tougher. You don't want the edge to get as hot and so once the correct temp. is indicated by the color at the edge, you quench to stop any more heat from spreading to the edge and making it too soft. If you were using an oven to temper there would be no reason to quench it.
 
yes; with that method, the heat you are introducing is still hotter than your tempering temp, so the spine of the blade will be hotter [and consequently become softer] than you want the edge to get. the quench interrupts that heat migration, prevents too much of it from reaching the edge, and resulting in over tempering.

the repeating would make sure the steel spends more time at that temperature.
 
Man, all you guys are a tremendous help! Thanks...

OK, so the tempering will have to wait until tomorrow night. I have used the belt sander and have a pretty decent (rough) edge on it. Does it matter if I leave it sharp or should I dull it up prior to tempering?

Thanks again guys, I look foward to giving it a shot tomorrow. I will update with results.

-WB
 
Talk to the cook.... not the chief cook, one of the ones your rank, they might be able to slip your knife in during the day prep. Since the ovens are usually at 450 (avg) it should be just right. Plus, you may be surprised at the reception you get when they find you are starting to make knives. When you get back, get hold of Stacy Apelt (bladsmth on the forums), he is in Norfolk and might be able to help you along.
 
agree with all above, but another thing is if you use a oxy/acetylene rig to heat up the steel, run the flame a little rich with some tail so that all the oxy is being burned. This might help keep your decarb down a bit more. When heating steel into the higher ranges oxygen is an enemy.
 
ib2v4u said:
agree with all above, but another thing is if you use a oxy/acetylene rig to heat up the steel, run the flame a little rich with some tail so that all the oxy is being burned. This might help keep your decarb down a bit more. When heating steel into the higher ranges oxygen is an enemy.
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Cool, I will keep that in mind. I ran the flame extreamly hot to speed up the heating process which led to (excessive??) decarb.

Off to the bench to give it a shot. I'm going to use the soildering tip to keep the flame low/managable. Wish me luck :D
 
when the steel is that hot, and there is free oxygen surrounding it, elements like carbon in the surface of the steel will burn. it seems like that leads to scale and decarb both.

the rich mixture would mean you're presenting something of a neutral or reducing atmosphere right where you're heating.
 
Wrenchbender.... there is no oven on the entire base? Toaster oven?... do you guys cook or have a mess hall? I can't believe a building full of gung ho mechanics doesn't have some way of making nachos... lol.

That would be the easiest/safest way.
 
On the oxy/acetylene rig I was referring to times when heating into the ranges for normalizing and hardening. Of course there is still going to be free O2 in the atmosphere. I don't think that a rosebud is necessary either, unless it was a huge blade, a cutting tip would be fast enough and have more control, just don't hit the level or you would have massive decarb in that area.:D
 
Rick Marchand said:
Wrenchbender.... there is no oven on the entire base? Toaster oven?... do you guys cook or have a mess hall? I can't believe a building full of gung ho mechanics doesn't have some way of making nachos... lol.

That would be the easiest/safest way.
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Unfortunatly, no nachos over here :mad:

UPDATE: So.....I think I might have overtempered it. I did it three times, makeing sure to avoid direct heat to the tip/edge. After I was done, I sharpened it and began testing it. Cut cardboard pretty well, cut paper like butter, did some chopping on a tree out back, whittled a little off of our picnic table end, couple good sticks into a 2x4, couple more good sticks in the knot of the wood, no deformation :D THEN, I got ballsy.....

Plexiglass was the tip's demise.......chipped half of the plexiglass and bent the tip :grumpy: Is this common or is the tip too soft now? Granted, I wont be stabbing plexiglass often with this knife, but I was looking for how hard a medium I could stab without bending/breaking the tip.
 
Wrenchbender_E said:
Plexiglass was the tip's demise.......chipped half of the plexiglass and bent the tip :grumpy: Is this common or is the tip too soft now? Granted, I wont be stabbing plexiglass often with this knife, but I was looking for how hard a medium I could stab without bending/breaking the tip.
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Performance under those conditions is more dependent on geometry than heat treat. Just about any knife with a fine point will fail if thrust hard into a ridgid medium like plexiglass.
Would have to see the goemetry of the tip to give you any more insight.
 
UPDATE: So, Im pretty sure that I overtempered it because I spent an hour tonight modifying the grind (went with a flat grind). It isnt too terribly soft, but is 0-1 forgiving enough to re heat treat and re temper? If not, its plenty hard enough for light use, but I'd really like to get it a bit harder...

-WB
 
As long as you didn't over heat it or do anything else drastically wrong on the first quench there should be no problem with doing it over, but you will have to remove the decarb layer again.
 
Thanks for the help guys! I re-did my HT tonight and re tempered it and man did it work out nice. Sharpened it up and took it to test......

-50 12'' cuts on corrugated cardboard
-whittled down three 3/4'' branches off of nearest tree (unknown wood)
-5 stabs through the side wall of an old light truck tire out back
-still shaved my arm like a razor :D

I will try to post pics sometime tomorrow in a new thread to get peoples constructive criticisms. I cant thank you guys enough! I'll be talking to you...
 
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