Thursday, May 27, 2010

Striking Knives

Here are some striking knives I made a few months back. All are made from a piece of 1/8" thick w-1 tool steel, 1" wide by 36" long, purchased from McMaster Carr. I made the three shiny ones first. Cut the steel into three 9 1/2" lengths, put masking tape on the face of each, and drew the outline of the striking knives on the tape. Cut the outline just shy of the line with a hack saw and finished them up with a half round bastard file and a flat mill file. Formed the 25 degree bevel with the file, but not all the way to a sharp edge; left about a 1/32" flat on the bevel so the edge wouldn't distort during the heat treating process. The finger cut-outs on the two were just made with the half round file. I find these to be very comfortable in the hand. The awl end was made by chamfering the edges with a file and then working them to round. The point was finalized on sandpaper stuck to a table.

Next came the heat treating to get them hard enough to hold a nice, durable edge. I heated the metal with a plumbers torch with mapp gas, which burns hotter than propane. I laid the metal on a bed of charcoal as to not let the heat dissipate so quickly. First step was to bring the metal to the "critical point" of approximately 1500 degrees fahrenheit. The metal becomes non-magnetic at this temperature, and that is how I determined when I had hit the appropriate temp. Once this level of heat is achieved and held for about 20 seconds, I quenched the metal in a coffee can filled with water. At this point the metal is extremely hard; way to hard to use. It is very brittle and too hard to be honed on sharpening stones. So the next step is to temper them to a useable hardness. I was shooting for somewhere around RC 60 or so. To achieve this hardness, I place the knives in a 425 degree toaster oven for about 45 minutes. This brings the metal to a nice straw color, which helps tell you that you're where you want to be hardness wise. I then polished them to a bright finish with progressively finer grits of sandpaper, the final, a wet-sand to bring them to a nice polish. Then a final sharpening on my oilstones to finish the shape of the bevel and give them their final honing.

The two shorter knives were made with the left-over length of metal I had. These were inspired by the striking knives that the blacksmiths at Colonial Williamsburg make for the cabinet makers and jointers. The process was the same for heat treating them. The twist in the middle was done by heating the metal cherry red and holding one end with a pair of vise grips and grabbing the other end with an adjustable wrench and twisting while still cherry. I put a point on the end of one of the knives and a tiny knife edge on the end of the other. On all five knives, only the bevel end was heat treated. The awl end was left soft so it can be easily shaped with a file or sandpaper.


Steve Branam said...

Nice! I was just reading Adam's article in "Hand Tool Essentials" about these and wondering how I could make one. So now I'll just follow what you did here.

Bob Rozaieski said...

Nicely done Jamie! How do you like the Williamsburg style knives? I've been thinking of making one or two myself. Also, how is the W1 to work & heat treat? I've only worked with O1 to date, but the W1 is kind of appealing to me. Seems like it would be more like the old cast steel, quenched in brine. Have you done any work with O1 that you could compare to?

Jamie Bacon said...

Thanks Bob! I really like the Williamsburg style knives. I find the shorter knife to be more convenient, plus I just plain like the look better. The W1 worked really well for me, although I have nothing to compare it to as I've never used O1. I wouldn't hesitate to use it again though. I'd love to try to make some square sided, tanged firmer chisels one of these days. I really like the look or the 18th and early 19th century tools.

Jamie Bacon

Caleb Dunn said...

I have recently found your blog and am enjoying it.
I have a question about the knives. Is there any particular reason you chose W1 over O1? I know you have not used O1, but I am curious why you chose what you did.

Thanks for your help.


Jamie Bacon said...

Hey Caleb. Glad you're enjoying the blog. No real reason for choosing W-1 over O-1 for the striking knives. I used O-1 for my chisels and will probably continue to just use O-1. I don't have enough metal working knowledge to know if one has any advantage over the other. They've both held an edge well though.

mike said...

hey really like the knives just wondering though is the W-1 tool steel hard enough after you heat treat it ? what I mean is, does it still dent or get nicked up ?

Jamie Bacon said...

Hi Mike. Glad you like the knives. I find I use the shorter Williamsburg style knives all the time. They hold an edge great and although I have no way of testing their hardness, they seem about the same as any of the chisels I own. I really don't think there's much, if any, difference in the hardness of W-1 and O-1 once hardened and tempered.