This blade belongs to Luke Freeouf, who post here as Lurkers. One of the things he was interested in was my impression of its edge durability.
To have a look at the edge durability I first just chopped up a fair amount of wood, (about 1000 chops total, not all on the same day). This was fresh wood, fir, pine and spruce as well as seasoned drift wood, and various scrap lumber. Knots were cut through frequently. The edge was fully sharpened, using waterstones and a CrO loaded strop, several times to enable the detection of even minor rolling. No damage was induced on the edge during any of the chopping.
The blade was then chopped into nails while they rested on a 4x4 pressure treated block. The nails would be driven into the wood from the force of the impacts, and cuts made up to about one quarter of the way through a three and a half inch common nail. The edge was not visibly damaged, just blunted. A 510 g ball pein hammer was then used to pound the knife into the various nails . Because the wood kept collapsing under the nail, the best that could be achieved was a cut about half way through the three and a half inch common nail. These various poundings (a half dozen) put small dents in the edge, from one to two mm wide, and the damaged region was up to 0.015" thick.
Some harder chopping into more nails was performed later. This time on harder wood which was higher up off the floor so I could get more power behind the knife. The cuts into the nails were deeper, the damage induced was more bending, but less extensive than the hammer assisted cuts. I then did some nail chopping on concrete. Since this didn't give like the wood, the blade cut far deeper into the nails. I could get penetration up to half way through the three and a half inch common nail. I then used a four and a half pound beach rock to pound the knife through the nails. The larger nails took one to two hits to be cut completely through. The damage from this was less than the hammer pounding, and the concrete tended to just mash the edge down a little in the impact areas, just blunting.
I then chopped into the head of the hammer. The knife made large cuts into the head, about one mm deep, and up to one cm long. This did no visible damage to the knife, just blunted it. I then found a piece of a concrete block that I had chopped up earlier and whacked that into little bits. These were hits heavy enough to break the concrete apart and send sparks flying. The rock contacts tended to mash the edge down, and you could see abrasion lines in the edge were the rocks had cut into the steel. A lot of impaction had taken place, but no direct fracturing. I then stabbed the tip into the pieces a half a dozen times breaking them up into smaller bits, some tip impaction, but nothing significant.
The attached picture was taken at this time.
Since the concrete didn't do any major damage I chopped into the beach rock a half a dozen times. This induced more impaction than the concrete, no surprise, it is a lot harder. I was hitting the rock hard enough to send it flying feet across the floor and producing visible sparks. The edge was impacted up to 0.035" across, the blade thickness was a little less than this behind the impacted region, about 0.025"-0.030". Again no fracture, you could clearly see the squashed steel. I then stabbed the tip into the rock, sending sparks flying and the rock shooting across the floor again. I did this a half a dozen times and it impacted the tip about one mm.
I then held the knife out at arms length and examined it for damage. You could tell that the regions that had been whacked into the beach rock were a little impacted, but overall it didn't look that heavily used. I took a few shots, and could not tell from the pictures that it had changed significantly from before. Cheap camera though, no ability to do close ups. So I take the blade and put it at a forty five degree angle and then give the edge a whack with the hammer. Success. This bends a piece of the edge enough that the ductility is exceeded and it tears off. This removed a piece of the edge about three mm long and the blade was 0.030" thick behind the damaged region. This damage was visible at arms length.
How was the cutting ability effected? After the concrete chopping the blade still had the ability to slice cardboard, chop wood, and slice various cords in the regions of heaviest damage. Though you could tell of course it was seriously blunted. After I whacked it into the beach rock there was no fine cutting ability left in those impact areas. You could still chop wood, but you were crushing it a lot, and the performance was seriously degraded. Of course there were lots of sharp areas left on the blade. Time to sharpen the blade on a small belt sander (1x30"), would be a couple of minutes, just a few passes per side would eliminate 90% of the damage, sharpening by hand, it would take less than half an hour.
The edge on the BM-E was the standard Busse asymettric edge, wider on one edge than on the other (0.038 x 0.058 -> 18.1, 0.048 x 0.089 -> 15.1).
-Cliff
