Hardness: Walk the line? Preferences

[David Schott]

For a large, heavy bladed knife that will mainly see heavy chopping, I obviously want no chipping whatsoever on the blade and want a tough blade that can take extreme abuse. I have a big blade made from O-1 that I am currently performing extensive tests on and it is walking a fine hardness line at this time. I ran it through two rounds of tempering and afterwards the blade passed the brass rod test so I sharpened up a section and did some chopping tests. The edge does not chip out whatsoever, but in order to attain that toughness, I feel it's edge retention is a bit low. I can cut a 2X4 and still shave, but can see some tiny dulling in the blade under magnification in lighting. Not doing much chopping normally, I am unsure of normal wear and tear caused by full force blows into wood/knots etc. I am at this point trying to gauge if I have made the blade a bit too soft. Can a blade pass brass rod tests and still be too soft? I have no hardness tester.

Blade skated a file post HT and a file will now slightly dig after temper. I am confident in my pre quench temps, as well as my quenchant temp and I am sure i got it below the nose for O-1 as I normall work in 1095 and harden with no problems and a much shorter quench window....Temper was 2 hours at 400, 2 hours at 425. Showed a nice straw color...nothing darker.

Any comments? Should the blade be able to take a 2X4 in half multiple times and show zero dulling whatsoever, or should the dulling simply be minimal enough to allow shaving,

 

[Stacy E. Apelt - Bladesmith]

Don't get all hung up on stuff like "I can cut a car in half and still shave with it." .That would only be a sign of how good a razor it was.A chopper will be tempered to a somewhat softer edge ,thus making it tougher.It can be quickly redressed and ready for more chopping quickly.Think of a Swedish double bit ax.It was tough and easy to resharpen.If it was made so hard it did not wear, it would chip all to hell.I have one used on my Grandfather's farm.It is still a good ax.
The edge flex test is a good test for a chopper.If there were no chips after the 2X4 ,then I would say you nailed the HT.

 

[LRB]

Just my opinion, but I believe your temper heat is much low. I get around 56 to 58 Rc at around 525o. 01 requires higher temper heats than do 10xx series steel, and other simple steels. I run mine at three one hour tempers, cooling to room temp in between. 01 holds a good edge even at Rc's in the low fifties, which is what Randall got his reputation with. At the temps you are running, assuming that you got full hardness in your quench, you should be up around 60 to 62 Rc. That is too hard for most customers taste. Many will bitch if a blade is too hard to sharpen.

 

[David Schott]

You know, after more testing, I think this one is too soft. I must have missed something in HT or had the oven cycle too high (though i saw no purples or broze in color) After doing some chopping on a block of hardwood, I found the edge to have degraded more than acceptably. I have worked in O-1 before and this one isnt up to par. I am going to simply re-HT and work on a longer soak. I think possibly my quench temp was too high, but either way, its going back in the forge. Just need to research re-HT again to figure out the cycles I will put it through. No biggie!

Thanks for the advice! I will go for a bit lower RC than normal since itll be seeing lots of abuse.