what defines abuse : more work with a ultra hard knife

[Cliff Stamp]

Awhile ago I made some comments about metal cutting :

http://www.bladeforums.com/forums/showthread.php?t=364976

Recently, inspired by an exchange Thom and Alvin were having on rec.knives I did some work with a 1095 paring knife, 66 HRC, 0.055" thick stock, hollow ground, edge is 0.010-0.012" thick, 0.2" back from the edge the knife is 0.021" thick.

I first used it to cut up some chicken :

http://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_paring_chickenhttp://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_paring_chicken.jpg

The breasts were cut off, the legs removed and seperated, the wings removed and the tips cut off, and the body cut into pieces with the tailbone removed. No damage to the knife, still shaved, multiple chickens went to parts when I changed to the utility knife (similar grind on 63.5 O1) which has a 20 degree microbevel so I could experiment and get sloppy and do things like :

http://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_utility_legs.jp
http://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_utility_legs.jpg

Note the cuts through the bone, plam on the tip, off hand on the handle, rock down and cut through the joint, hard tool steel is a wonderful thing. Back to the paring knife :

http://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_paring_bone.jpg

Carve up an rib bone like a piece of pine, I got sloppy with the work near the tip and there was some side torquing when I started to hog material off, more than 1/16" deep slices and due to the leverage issues with cutting with the tip the edge rolled a little, yeah it rolled, it didn't chip. When steel gets really thin it gets flexible even at this hardness.

Now we do some work which gets commonly gets the abuse label :

http://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_paring_cat.jpg

Using an icepick grip I cut one inch down into the sod to make a small rectangle. The front of the sod was then cut at at 45 degree angle so I could peel it back al little then I simple skinned it off, cutting it easily with the knife.

http://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_paring_hole.jpg

No visible damage, though it was blunted :

http://i7.photobucket.com/albums/y269/CliffStamp/Alvin/alvin_paring_after_so
d.jpg

The first inch near the blade could still do clean press cuts, near the tip the cuts were ragged and needed some back and forth slicing. I reset the edge with waterstones, no micro-bevel, <2 minutes. All of the above work was done with a primary edge bevel of 2-3 degrees and a secondary edge bevel of about 5 which is so small you can't see it, even under 10 x mag it isn't apparent.

-Cliff

 

[me2]

Just a note Cliff. I rechecked the data I had from the hardness tests on some quenched but untempered O1. The average was 63.5, the high was 64. I think I over heated it a little, the grain on fracture was quite coarse on one side. This side had a lower hardness, but only after being tempered. Anyway, you're beginning to make me wish I had just tempered it at 300 degrees and aimed for the 63 hardness.

 

[Alberta Ed]

Interesting -- 1095 is good stuff. Have you had a chance to play with Roselli's UHC steel?

 

[Cliff Stamp]

Interesting -- 1095 is good stuff.

Yes, lots of potential there, the O1 blade I have is really nice as well, I also have a M2 blade which is similar which I need to do more work with. The combination of grind and steel properties allow for some very efficient sharpening, with the above paring knife, the edge was damaged only ~0.1 mm in maximum depth and only required at 1000 grit waterstone to reset the edge, followed by a soft chinese waterstone and CrO.

I rechecked the data I had from the hardness tests on some quenched but untempered O1.

I went over some stuff myself, you can get O1 up to 65 HRC according to the graphs in Allen book, however 63.5 HRC corrosponds to the peak in the torsional toughness, and this is *very* sensitive to tempering temperature, just a small percentage off can reduce the toughness to a fraction, the peak is *really* sharp :

http://www.panix.com/~alvinj/graph1095.jpg

This is for 1095, not O1, but the same behavior follows, note how leaving the hardness down to ~58 which mainy people do for toughness actually *decreases* the torsional toughness to less than half of maximum.

-Cliff