|chef's knife work
||[Jul. 19th, 2004|10:54 am]
About a year ago, I started working on what would hopefully become a unique, original, and functional chef's knife. I started with a 1" diameter piece of round L6, and forged out a blade. Sadly, at that point, I got distracted, tossed the piece into the annealing trough, and pretty much forgot about it.
While cleaning up the workshop a bit this weekend, I came acoss it, and started working on it again. Now, 1" of solid steel is quite hefty. I allocated 4" of solid stock for the handle, as I was planning on single-piece construction, and 4" for the blade. Yes, just four inches. You see, even forging the piece out to 1/4" thick lengthened it to about 8" of blade, and after drawing out the point and forging in the bevel, it exceeded 12" in length. I'll be shortening it a bit during the profiling and grinding.
As I was using this for, among other things, power hammer practice, I left the blade portion attached to the main piece of stock for the initial forging. Trust me, 3' of 1" steel is a bit on the heavy side -- roughly 32 lbs. So it was a bit of a workout, but I think the extra mass helped in both keeping the rod from heating up excessively and in keeping the blade controlled under the 50 lb ram. I use a combination die, one-third texturing, one third flat, and one third drawing, which I've ground a 15 degree bevel into for assistance in forming edges.
Once I had the blade drawn out and roughly tapered, I cut off the knife material, leaving an extra inch on the handle end to forge in an extension that I could easily grip with tongs. When you have red-hot steel being violently thrashed by a 50lb hammer 300 times a minute, you need controll, or else you're going to have a red-hot knife blade flying around the shop. Nobody wants that.
That's where I left off a year ago. I had a piece of steel 18" long -- 4" of round handle, a 2" nub for the tongs, and a bit over 12" of blade. I had used the beveling section of the bottom die to taper the blade towards the edge a bit, but not to the extent I needed, and the material in general was thick -- over 1/4" at the spine, still over 1/8" at the edge, and the width at the widest section was about 2". Obviously, more work was needed.
When I picked this up again, then, my first concern was to forge in the edge bevels. When forging in a bevel, in essence you're streaching out the edge, making it longer as well as thinner. This tends to turn the blade into a scimitar-shaped thing. To compensate for this, I first bent the blade into almost a U-shape, with the bevel on the inside of the U. Heating to a nice orange glow and whacking the back of the blade against the anvil did this nicely, only needed to flatten out the blade a couple of times and three heats. To forge in the bevel, I used the power hammer, alternating sides to ensure the stresses and beveling were even. This took about four heats to do the entire blade. The blade was now over 2.5" in width, about 1/16" in thickness at the edge, and about 12.5" long. I was carefull to not overheat the blade during this operation, as this forging is refining the grain structure of the steel around the edge, and while the upcoming heat treatment would make more of a difference, why push things.
WHen I was done, there was a bit of curve past the straight point from the beveling. One more heat and a few whacks against the anvil an I was done forging the blade.
Since this is to be an integral handle, that's where I turned my attention next. I had thought about forging in finger cutouts, but decided that since I hate those, I'd go for a smoother design, with more flowing lines. I wanted a somewhat flattened elipse crossection, so I heated the handle portion and under the power hammer flattened it to about 3/4" thick, with some resulting elongation and widening of the handle. I decided I would grind in some of the lines of the handle, but wanted the base to be thicker than the rest, so I cut off the tong-nub, heated the end to a nice, high temperature, set the knife in the post vise, and whacked it a whole lot with a hammer. The result is a noticible thicker end. yay.
After some final tweeking of the blade, making sure the blade and handle were aligned, that the blade was straight, etc, I heated the blade up to critical and air-cooled twice to normalize, then once more and into the vermiculite filled annealing trough. These steps reduce the stresses in the blade, reducing the chances of warpage, cracking, and twisting during the upcoming final heat-treatment. Before I do that, though, I'll need to do the initial grinding, because normalized, annealed steel is much easier to grind than the hard stuff. Not only is is softer, but you don't have to worry about the temper if it hasn't been hardened and tempered yet.
Earlier, I also finished off a knife. Sweedish saw blade steel, offset handle design based off of a "Knives and Scabbords" design, olivewood handle slabs, brass tubular pins. Nice looking piece, once I get the final polish on it I'll post some pictures and put it up for sale somewhere.
Enough for now. Be well.