Blade Failure! - Need Help

[tejas7]

Today I tested an old O-1 blade that I had laying around and never fininshed. It was 1/8" thickness, about an 3/4" wide and about 5" long cutting edge. Put it in the vise about a third of the way from the tip. It bent close to 90 degress and then more or less snapped.

I quenched in oil, double tempered at about 350 degrees and then drew back the back of the blade to a nice blue color with a torch (about half to two thirds of the blade width and almost the entire length)

I would have expected the blade to crack at the edge but not all the way through. Where do you think I went wrong?
My 5160 blades hold up much better. What can I do to get better perfomance out of my O-1 steel blades?

[This message has been edited by tejas7 (edited 04 October 1999).]

 

[Kisu]

First, I'm a little concerned about the OA length of the blade, it seems a little short for torture like that. Secondly, I always temper my 01 blades at 425 for an hour 3 times. Also, did you make sure that your oil was hot enough, it needs to be hot enough that if you stick your finger in, you can't hold it there, but not hot enough that it auto-burns you. Hope this helps.

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KSwinamer

 

[goshawk]

My suggestion would be to build a different
quenching tank and buy a meat thermometer
from the local grocery store for about 4.00.
build a small quenching tank with an adjustable table in the tank. This way you
can adjust the hardening level and have it
the same in the case you want to also do
multiple quenches and you don't have to
bother with drawing the back. heat the oil
to about 160 deg. F. 01 would do better
with a hotter temper and more than one.
As far as the length of blade a four or five
inch is what is a normal length for a fixed
blade and is more practical for a test blade
because that close to what a person makes.
One of the best things to do is to use the
brass rod test after you temper to check before you put it in a vise to bend -- if
it will pass the brass rod test it will usually pass the vise test. This way you can
temper it again while it is in one piece.

Goshawk

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http://www.imt.net/~goshawk
Don't walk in tradition just because it feels good!!!!!
Romans 10:9,10
Hebrews 4:12-16
Psalm 91

 

[tejas7]

All good advice. I usually follow all of those steps. I will try a little hotter temp on my quench oil.

I am curiouse as to the performace of an edge only quench on a piece of 1/8" thick O-1. Wouldn't the spine be "too soft" if left in the totally annealed state? Would it be too prone to bendning as opposed to being more of a spring temper?

Also - I have had conflicting thoughts about how high a temp to use for tempering O-1. I know that the factory specs say 425 degrees would be about right but have read on this forum that 325 to 350 produce the desired effect because of the edge of the knife being so thin? Comments?

[This message has been edited by tejas7 (edited 04 October 1999).]

 

[DanL]

On doing the brass rod test, do you press on it just enough to get it to flex a tiny amount? If I do it this way it will return to normal but if I press more it leaves a permanent dent.

 

[Osbourn]

One thing that I did to get more of a spring temper on 01 is to edge only quench, then spray the back with WD40 while still hot. I would suggest having a large fan pointed right at you while doing this, though. It makes a huge cloud of gas that may be explosive. I didn't test the cloud, I just got away from it, because I was stupid and didn't anticipate it's presence.

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Oz

"When your work speaks for itself, don't interrupt."
- Henry J. Kaiser