For a while now I've been trying to put a handle on a convex puukko blade I made. I finally found a way and thus began testing the knife.
First a quick description. The blade is made from a mechanical hacksaw blade I recieved from Sodak here on BF. I believe these are M2 from Dave MacDonald. They are not soft back or bi-metal. The tooth and spine sides react the same way to a file; just scratched paint. I believe Alvin Johnson on rec.knives had one tested for hardness and got a 64 to 65, which agrees with the hardness for the "standard" heat treated condition of M2 in my Smith's Engineering Alloys textbook. The blade is 5 inches long, 7/8 inch wide, 1/16 inch thick with a clip point that I'll probably sharpen the back of at some point, but not yet. The blade is basically a very small machete, with about a 10 degree convex edge ground on the tooth side with no other primary grind. A small, barely visible microbevel was applied using the 20 degree slots on the sharpmaker, followed by stropping on 0.3 micron honing film from the local woodworking shop. This produced an edge that would shave nearly 1/4 inch above the skin of my arm. This same kind of edge can also be produced using a leather belt on a belt sander after 24, 80, 120, and 320 grit belts. The handle is cherry wood, slotted down the back and the 1/2 inch wide, 4 inch long tang epoxied into the slot. The hardest part was finding a saw that cut the same thickness as the blade.
Now for the testing. First, I dropped the blade point first from head height onto concrete. The tip survived and was resharpened with the Sharpmaker and strop. Given the hardness, I actually expected the thing to shatter, but its very light.
After resharpening, I tried some cutting tests. First was a piece of typing paper folded in half lengthwise twice and stood on end. The knive cut this pretty easy. I tried the same cut with some construction paper and the bottom half of the paper was left standing on the table. After that, I tried an empty 24 oz soda bottle. The knife cut the bottle in two. A near perfect swing is needed to get 2 pieces. The blade length is short enough that I have trouble getting all the way through the bottle without being very careful.
Next was some twisting cuts into and out of pine, then cherry wood. The blade was pushed into the wood the full depth of the edge bevel, and twisted out. No chipping or dulling. Next the point was given the same treatment. No damage to the point.
The blade was chopped into the edge of the opening of a 2 liter soda bottle. No chipping occurred from the impact with the hard plastic. Again, this is a very light knife, and really has almost no chopping ability, so the impacts were not very hard.
Next some wire bread ties were cut, using the Sharpmaker case as a cutting board. Again, no chipping. Some shavings were cut from an unhardened piece of 1095. Some damage to the edge happened here, the depth of the microbevel, which is less than 1/64 inch wide. The blade was sharpened again with the Sharpmaker and strop, so the damage was not extensive. Its difficult to tell if the edge rolled or chipped.
Next, the knive was held in one hand and batoned into a 1x10 pine board using a 4 lb hammer. The corners of the spine were rounded, but it was very slight. Again, it was difficult to tell if the corners were chipping or denting/rolling. The spine also appear to leave marks in the face of the hammer. I didnt check before I started, but there were 3 or 4 straight lines in the hammer face when I finished.
The final test so far was to dig a hole in the 1x10 using the tip. This was done with no damage to the blade, but the handle showed some separation from the blade at the blade/handle shoulder. The separation was barely noticable, and does not appear to be progressing. This is just a failure of the epoxy bond during the prying/twisting used to dig the hole in the wood. Sandblasting the blade prior to putting the slotted handle on would probably stop this, but I have no way to do so. Putting some pins or rivets in would stop handle worries as well, but I havent been able to make holes in the tang.
The knife is currently serving kitchen duty. The handle needs a new coat of oil and polyurethane. The edge bevel will darken slightly and turn a very light orange if left wet or used on fruit, but the color comes off with a good scrub with a Scotchbrite sponge. The unground portion of the blade has had no rust issues. I left it the flat gray color that remained after I wire brushed the paint off. So far a good knife for the cost of 4 sanding belts ($7) and about an hour to slack belt sharpen an edge onto what is basically a very hard piece of sheet metal. Thanks to Sodak for the material. I have a 1/8 inch thick saw blade left, but I dont think my Harbor Freight 1x30 sander is ready for that. Neither is my lower back, since it would take about 3 hours to grind given the time this one took.
First a quick description. The blade is made from a mechanical hacksaw blade I recieved from Sodak here on BF. I believe these are M2 from Dave MacDonald. They are not soft back or bi-metal. The tooth and spine sides react the same way to a file; just scratched paint. I believe Alvin Johnson on rec.knives had one tested for hardness and got a 64 to 65, which agrees with the hardness for the "standard" heat treated condition of M2 in my Smith's Engineering Alloys textbook. The blade is 5 inches long, 7/8 inch wide, 1/16 inch thick with a clip point that I'll probably sharpen the back of at some point, but not yet. The blade is basically a very small machete, with about a 10 degree convex edge ground on the tooth side with no other primary grind. A small, barely visible microbevel was applied using the 20 degree slots on the sharpmaker, followed by stropping on 0.3 micron honing film from the local woodworking shop. This produced an edge that would shave nearly 1/4 inch above the skin of my arm. This same kind of edge can also be produced using a leather belt on a belt sander after 24, 80, 120, and 320 grit belts. The handle is cherry wood, slotted down the back and the 1/2 inch wide, 4 inch long tang epoxied into the slot. The hardest part was finding a saw that cut the same thickness as the blade.
Now for the testing. First, I dropped the blade point first from head height onto concrete. The tip survived and was resharpened with the Sharpmaker and strop. Given the hardness, I actually expected the thing to shatter, but its very light.
After resharpening, I tried some cutting tests. First was a piece of typing paper folded in half lengthwise twice and stood on end. The knive cut this pretty easy. I tried the same cut with some construction paper and the bottom half of the paper was left standing on the table. After that, I tried an empty 24 oz soda bottle. The knife cut the bottle in two. A near perfect swing is needed to get 2 pieces. The blade length is short enough that I have trouble getting all the way through the bottle without being very careful.
Next was some twisting cuts into and out of pine, then cherry wood. The blade was pushed into the wood the full depth of the edge bevel, and twisted out. No chipping or dulling. Next the point was given the same treatment. No damage to the point.
The blade was chopped into the edge of the opening of a 2 liter soda bottle. No chipping occurred from the impact with the hard plastic. Again, this is a very light knife, and really has almost no chopping ability, so the impacts were not very hard.
Next some wire bread ties were cut, using the Sharpmaker case as a cutting board. Again, no chipping. Some shavings were cut from an unhardened piece of 1095. Some damage to the edge happened here, the depth of the microbevel, which is less than 1/64 inch wide. The blade was sharpened again with the Sharpmaker and strop, so the damage was not extensive. Its difficult to tell if the edge rolled or chipped.
Next, the knive was held in one hand and batoned into a 1x10 pine board using a 4 lb hammer. The corners of the spine were rounded, but it was very slight. Again, it was difficult to tell if the corners were chipping or denting/rolling. The spine also appear to leave marks in the face of the hammer. I didnt check before I started, but there were 3 or 4 straight lines in the hammer face when I finished.
The final test so far was to dig a hole in the 1x10 using the tip. This was done with no damage to the blade, but the handle showed some separation from the blade at the blade/handle shoulder. The separation was barely noticable, and does not appear to be progressing. This is just a failure of the epoxy bond during the prying/twisting used to dig the hole in the wood. Sandblasting the blade prior to putting the slotted handle on would probably stop this, but I have no way to do so. Putting some pins or rivets in would stop handle worries as well, but I havent been able to make holes in the tang.
The knife is currently serving kitchen duty. The handle needs a new coat of oil and polyurethane. The edge bevel will darken slightly and turn a very light orange if left wet or used on fruit, but the color comes off with a good scrub with a Scotchbrite sponge. The unground portion of the blade has had no rust issues. I left it the flat gray color that remained after I wire brushed the paint off. So far a good knife for the cost of 4 sanding belts ($7) and about an hour to slack belt sharpen an edge onto what is basically a very hard piece of sheet metal. Thanks to Sodak for the material. I have a 1/8 inch thick saw blade left, but I dont think my Harbor Freight 1x30 sander is ready for that. Neither is my lower back, since it would take about 3 hours to grind given the time this one took.
I knew this would be difficult when I asked a couple of makers if I sent them the blank would they grind it out for me. They all kept referring me to other makers. Oh, <insert name here>, he'd do a good job for you... 