I finished a home made M2 steel blade today and tested it for toughness, and a little edge holding. The blade was ground from a mechanical hacksaw blade sent courtesy of Sodak here on BFC. The blade shape is straight backed with about a 5" radius up to the tip. I think thats about the radius on the dinner plate I used to trace the sweep from the straight portion of the edge up to the tip. The edge is ground at about 15 degrees, convex from the full thickness. Think of a puukko with a 3/8" wide convex bevel on 1/16 stock. The handle and blade are both ~5" each.
Wear resistance is impressive. It took about an hour and two 24 grit belts on a 1x30 sander to put the bevel on it, and that was bearing against the platen. The convexing came with the 120, 180, and 220 grit belts used for polishing/sharpening. The edge was finished on a 1x30 leather belt after the 220 grit convexing. One of the sharpest blades I've ever done off the sander. Shaved hair a full 1/4" inch above the skin, maybe more.
Now for the toughness testing. I've been rereading Wayne Goddards first book, The Wonder of Knifemaking. A very good read for the beginning knife maker or, in my case, wannabe. One test he mentions is the floor drop test. A maker he met tested an O1 blade at 64 HRc and it broke into 4 pieces after dropping onto a concrete floor. I figured what the heck, I'll give it a try. 6' drop onto the point and onto the flat of the blade produced some scratching of the tip and a small chip, but no fracture. Then came the throwing test. I missed my target, a cardboard box, and hit a 2' diameter circular saw blade in the garage, tip first. The tip broke after this, but the portion lost was less than 1/16", equivalent to the damage done by a careless pass on the 120 grit belt during grinding/sharpening. Still no catastrophic fracture though. Impressive, considering these blades test to 64.5-66 HRc for hardness. The drops onto the flat didnt have any noticable results. I then split a 20 oz. soda bottle through the bottom with nothing more than glue from the label noticable on the blade.
There is about a 4" portion of the straight edge that I can do edge holding testing on, provided my sander still works. It was making a horrible racket during the last steps of sharpening. I want to resharpen fully before testing edge retention, since what is now the edge used to be the tooth side of the blade, and has seen some personal time with a 4" grinder to remove the teeth.
Next on the list, an M2 Bowie and Santoku, Pohan Leu style, from a 1/8" x 24" blade I have left over.
Wear resistance is impressive. It took about an hour and two 24 grit belts on a 1x30 sander to put the bevel on it, and that was bearing against the platen. The convexing came with the 120, 180, and 220 grit belts used for polishing/sharpening. The edge was finished on a 1x30 leather belt after the 220 grit convexing. One of the sharpest blades I've ever done off the sander. Shaved hair a full 1/4" inch above the skin, maybe more.
Now for the toughness testing. I've been rereading Wayne Goddards first book, The Wonder of Knifemaking. A very good read for the beginning knife maker or, in my case, wannabe. One test he mentions is the floor drop test. A maker he met tested an O1 blade at 64 HRc and it broke into 4 pieces after dropping onto a concrete floor. I figured what the heck, I'll give it a try. 6' drop onto the point and onto the flat of the blade produced some scratching of the tip and a small chip, but no fracture. Then came the throwing test. I missed my target, a cardboard box, and hit a 2' diameter circular saw blade in the garage, tip first. The tip broke after this, but the portion lost was less than 1/16", equivalent to the damage done by a careless pass on the 120 grit belt during grinding/sharpening. Still no catastrophic fracture though. Impressive, considering these blades test to 64.5-66 HRc for hardness. The drops onto the flat didnt have any noticable results. I then split a 20 oz. soda bottle through the bottom with nothing more than glue from the label noticable on the blade.
There is about a 4" portion of the straight edge that I can do edge holding testing on, provided my sander still works. It was making a horrible racket during the last steps of sharpening. I want to resharpen fully before testing edge retention, since what is now the edge used to be the tooth side of the blade, and has seen some personal time with a 4" grinder to remove the teeth.
Next on the list, an M2 Bowie and Santoku, Pohan Leu style, from a 1/8" x 24" blade I have left over.
