BARR KNIVES

ESSAY ON FITTING FITTINGS

The fittings or furniture of a knife determine its visible quality. The choice of colors and textures and how well the transitions between them are implemented are crucial to a well sorted out design. I decided that I wanted to include some mokume-gane in the Project knife, as its manufacture is one of my more eclectic skills. Mokume-gane translates to wood grained metal from the Japanese. What I make is straight layers of copper and brass. I made some a few years ago, just one small piece, which I cut in half and gave away one piece and the other piece has remained more or less in a state of misplacement ever since. It surfaced briefly recently while I was cleaning my car, and reminded me of its possibilities. The first time I made mokume-gane, I did it in my propane forge, which in retrospect seems like the manly-man way of doing it. The fire, the heat, the roar of the burner, the molten brass running all over the place, the occasional smell of burning hair.

This time I am doing it in my electric furnace and utilizing some new information gained since the last time. First I made a press to hold the sheets of brass and copper together during heating. Elemental copper and brass should fuse together at between 1500-1600 degrees Fahrenheit. Most steels have also lost most of their strength at that temperature, and that has to be considered when making and using the press. Staying within the parameters of what's laying around, I cut out two rectangles of ¼ inch thick O1 toolsteel, marked and drilled holes in each corner for some bolts to go through to squish the plates together.

Shown here is the press after one use, and the first piece of mokume-gane that I made this time around. The things that I learned since my first try are to coat the surface of the press plates with acetylene soot so that the product doesn't stick to the press. My original batch of years ago suffered some overheating in the forge that caused a partial meltdown and some difficulty in removing the ingot from the press. This time things were completely different. I made the press in about an hour, cutting and cleaning up the sheet copper and brass took about another hour, and assembled the press with the stack of clean metal in it. I put the whole thing in the furnace an programmed it to heat at 2500 degrees per hour up to 1550 degrees and then hold for an hour. This was at about midnight, and by the time it got up to temperature I was getting pretty tired. I decided that ½ hour was a long enough soak time and shut down the furnace and went to bed.

Even though it is a top-quality furnace, my house is built completely of cedar, which has all the fire resistance of a pile of shredded paper. I also resisted the urge to take out the press and look at it/hammer on it or otherwise mess with it while hot. At 1550 degrees in normal air it takes about 30 seconds to cause about six months worth of oxidization to a piece of O1 toolsteel. By 6:00AM the furnace was down to 212 degrees, and I took the billet out and ground the sides flat so I could see what I had. After grinding I had a billet about 1x 2-½ inches. But when I put it into the vise and tried to break the laminations, it split between two of the layers, ech! The goal is to get the two dissimilar metals to fuse together so that the billet act like a solid piece of metal, but one of the joinings, actually all of them were incomplete, essentially trashing the billet. The next batch I will sand both sides of each layer of metal before cleaning and stacking them. I'll go up in temperature a bit, maybe to 1600 degrees.

The melting range of brass alloys begins at 1630 degrees, Copper at 1981 degrees, which should make 1630 degrees the absolute maximum temperature that I can apply to this combination of materials.

A post-mortem examination showed oxidization around the perimeter of the billet, while the center of the individual metal sheets looked almost untouched.

My Machinery's Handbook shows that wrought iron decreases in strength at 1475 degrees to 15 percent of its strength at room temperature. The oxidization patterns, and the localized bulging of the billet in the center when hot suggests uneven clamping pressure. The initial clamping of the billet pinched off the periphery of the pieces, leaving an air pocket between each layer. I can easily imagine that as the air pocket heated up, it expanded and distorted the press because of it reduced hot strength. When there is enough heat, the oxygen in the trapped air forms a layer of oxide that prevents the fusion of the layers.

The next attempt will incorporate thicker plates for the press and I will compress the stack in a vise first, applying force to the center of the stack to drive out any trapped air between the layers.

An inquiry among the Knifemakers Listserv members got more information, which pointed to insufficient heat as well as a tendency to overtighten the press plates. I cut out some new press plates from a different steel with a better hot-strength. The next batch I ran up to 1630 degrees and still didn't see any "sweat" on the billet, and that is supposed to be my visual indicator when the piece is done. I kept increasing the temperature in the furnace over the next few hours finally giving up at 1800 degrees at something like 2AM. The next day I had success at 1850 degrees, but with more localized melting than I would have liked.

At some point I realized that the center of the billet wasn't necessarily getting as hot as the temperature as the furnace pyrometer indicated. No problem with the instruments or materials, but in the soak time. It takes a while for heat to propagate through a dense solid, and my mokume billet was sandwiched between two thick pieces of steel, insulating it from the heat of the furnace. I decided on ½ hour at 1750 degrees, and less peeking. Every time I opened the door to the furnace to look at the billet, the temperature dropped 200 degrees and took a while to get back up.

Here the billet is squished in the vise for good measure after soaking at 1750 degrees for 30 minutes. After several failed billets, I am now in the ballpark with a half-hour soak at 1749 degrees. I had a bit of melt down in one corner of my latest and largest billet, but the distortion it caused actually looks pretty good.

Only my last two billets turned out to be fully fused. I tried to cut out some dowel pins from the billets that I had produced, and made a lot of shiny metal pretzels.

Cutting this layered metal on the lathe or with the mill proved to be quite a challenge because even the smallest delamination will grab the cutting tool and bend the soft metal into a pretzel and sometimes take the cutting tool with it.

This was also a problem when lathe turning and cutting the material, and probably why I have never seen mokume-gane pins on a knife before. It's tough to make them!

Now that it is no longer appropriate for me to go on and on about mokume-gane, I'll give a brief description of the metal I will use for the finger guard and butt-bolsters. It's brass. You know; the yellow metal that looks like gold right after it is polished. It is nice and soft and provides a nice color to most any knife, and takes a great polish.

The fitting of the fittings is the baseline level of quality in handmade cutlery. There should be no gaps between pieces where there shouldn't be and working clearances on folding knives should be as small as possible while still allowing smooth operation. Once you have seen and appreciated a well-crafted handmade folding knife, you can see why they are priced hundreds of dollars more than similar factory-made knives. Attaching metals and hardwoods together without any visible gap is no small feat. First, the surfaces must each must be perfectly flat, and then must be fastened in a way that is strong enough to do the job and leaves as little evidence of the joinery as possible. The latter is the most difficult.

Using the standard finger guard as an example; first lets look at the mating surfaces. On the blade there are three external surfaces which meet up with the three internal surfaces of the slotted, U-shaped guard. The best way to get the surfaces to mate is to make sure that the flats on the blade are parallel, and that the sides of the slot in the guard are also parallel and of the same width as the thickness of the blade. I understand that there are knifemakers who can do this by hand with files, but I never spent enough time practicing at it. The common practice is to do it with a milling machine and large diameter cutting wheel.

One of the shortcuts many makers use to apply guards to blades is to solder them in place. This provides a fairly strong bond and fills any gaps left when fitting the guard to the handle. This gap-filling effect has the obvious advantage of filling in mistakes, but it is difficult to color-match the solder to the guard material or blade steel. It looks obvious, and the gaps that between the parts are still visible, they're just full of solder. The best way to attach metal to metal is with the use of pins or screws.

I haven't used screws yet to attach anything to my knives, but I did use a type of bolts on a few knives. At the time I liked the bolts because they could help mask the poor fit of my handles by screwing 'em down tight and closing those gaps. But it was at the cost of having a knife handle that is in constant tension. Screws are primarily used on folding knives in the current market, because they are easy. I'm just not into folding knives yet and when I do start on folders, I may start liking them more. I left J.P. Moss's studio with a certain reluctance to use screws in knives. Aside from "tactical knives" that are popular now, there are no classic designs that I can think of that use exposed screws.

Now I'll talk about how I prefer to do it. I use dowels of the same material as the furniture, in this case, brass. First I drill through the brass at locations marked by using the knife blade, which already has holes in it at the guard and butt area. After drilling the brass with a .125 drill, I countersink the ends of the holes, which makes them a little funnel-shaped at the ends. The pins are then cut from .125 diameter brass stock and the ends are shaped into little domes so they are just long enough to stick out of the holes about .1 inch on either side. The top surface of the guard is polished and slotted to the thickness of the knife blade and the parts are assembled. On a flat hard surface the pins are peened with the hemispherical end of a ball peen hammer. This flattens out the little domes so they completely fill the funnel shaped cavities in the drilled pin-holes.

After the pins are peened over, the part is shaped on the belt grinder and if the peening was done right, they are invisible, making the joinery very unobtrusive, and giving the impression of fragility where there is actually great strength.

To illustrate what a decent fit and finish looks like, I will compare two folding knives, one factory made and the other the knife I made at J.P. Moss's shop. The factory knife was given to me as an award for ten years of service at FedEx, and is a typical $70 knife with a sterling silver "FedEx logo" inlay on one side of the handle. In the side view there is little to indicate any dramatic difference in the quality of the two, except for my name on the top knife.

The view of the spines of the knives tells much more about the engineering and manufacturing processes put into each. They are both lockback folders, which means that the blades lock in the open position.

The central part of the spine of both knives is called the locking bar, and the depression on the left end of them is where you push the locking bar to release the blade. There is a clearance gap between the far-left end of the locking bar and the rear spacer piece. That gap on the upper knife appears as a straight line less than one hundredth of an inch wide. On the FedEx knife the corresponding gap is irregularly shaped and goes from three hundredths to six hundredths wide. The blade end of the locking bar should have no gap at all, since that end of the locking bar and the blade are supposed to be in contact in order to firmly lock the blade in place. On the upper knife there is a line where the two pieces of metal meet as two perfectly flat surfaces. On the lower knife there is clearly not such a close fit. It locks up all right, but looks like hell in comparison. Impossible to put on paper is the action of the knives when opened and closed. The smoothness of the pivoting action of a knife is called the "walk" and the snapping sound as the knife is fully opened and the locking bar engages the blade is called the "talk". Let's just say that the walk and talk of the handmade knife is far superior to the factory knife. And if you really must know the difference, go to a knife show or call me. I can only do so much on paper.

If, after reading this, you begin to start looking at knives and handcrafts with a more critical/jaundiced eye, then I will feel I have done my job to spread the word.