Grinding

After the blades are forged to shape they must be finish shape prior to heat treating. This may be done entirely with hand tools, i.e. files, stones and paper, or power tools may be used. It is not necessary to invest $1,000 in a grinder before you can make a knife. Details on shaping and finishing a blade can be found in Sword Class notes

Grinders

I use three basic grinders in my shop. The picture above is a Burr King grinder. It has a variable speed motor and is shown set up with a flat platen. The Burr King is a quiet running machine with good control and is very adaptable. It is also very expensive.

The second machine is a Bader grinder set up on a two horse single speed motor. I have had this grinder for fifteen years and it still runs fine. Bader has recently come out with a new model based on a design by George Herron. This is a great improvement and would be my first choice if I were starting up. Both of these machine run 2x72" belts.

The third grinder in my shop is a horizontal disk grinder. I made this machine when I first started knifemaking. It has an eight inch disk machined from a 3/4 steel plate and has been trued and balanced. It is driven by a 3/4 hp DC motor with controller that allow you to have infinite speed control and reversibility. I use spray adhesive on the disk and trim sheet abrasive to fit.

Grinding Sequence

Starting with a forged blade, I use the Bader first with a worn 60 grit belt and profile the blade. With forged blades profiling is very quick because the blade has already been shaped, but the grinder is used to clean up the lines. After the blade is profiled, I sight down the edge and then grinding edge up I put a mini bevel to establish the center line of the edge. This is done by eye and will serve as a guide when I am grinding the bevels.

Almost all of the blades I make are flat ground, but I use the eight inch contact wheel on the Bader to take off the scale and some of the stock from the flats of the blade. I am careful not to grind too much with the wheel or I will take off too much stock. Next I got to the Burr King and the platen. Using a fresh 60 grit belt and running the grinder at a moderate speed, I begin to grind the bevels on the blade.

When working on a grinder it is important to maintain a solid position in relation to the belt. I lock my elbows to my sides and holding the blade edge up in my hands, move the blade across the belt by shifting my weight from one leg to another. You can not grind accurately by holding the blade loosely in your hands, you must lock down.

I begin my flat grind at the plunge, or the area nearest the ricasso. Tipping the blade slightly, the belt grinds from the edge bevel back. You must move the blade across the belt with the motion of your hip making sure not to linger in one spot longer than another to keep the grind even. I suggest light to moderate pressure at this point until you get the feel of the belt and establish a flat to grind to. With the edge up and the tang in your right hand, draw the blade across the belt to the point. Do not tip the blade to get the point, you will grind the flat of the blade first then grind the point and feather it in. So you are grinding at this time from the ricasso, right to left. With a fresh belt, this will go quickly and you must be careful not to remove too much metal.

You should keep the blade parallel to the platen. If you tip the blade in on the right and move across the blade the top of the grind line, that is the cut closest to the back of the blade will rise. If you tip the blade in on the left, or tip end, it will tend to bite into the edge. Adjust your pressure on the blade until you are in control and are taking off metal at a rate that you are comfortable with.

I grind bare handed. This will give me reason to pause and take my time. Most grinders like to keep a bucket of water directly below the belt to catch the hot sparks and hold down on the dust, also to keep the blade cool by quenching in the water frequently. Breath is very important in maintaining a steady grind. It is much like shooting a rifle, you take a breath and hold while you make your pass. As you become more comfortable with the grinder and can relax, your breathing will become steady and even. If you find that your concentration is wandering, stop and gather yourself. I check the blade frequently as I am grinding, checking my lines and correcting for any variance. I grind on one side until I have established the flat and can track the grind down the length of the blade. Before I have reached the top of projected finish point, I switch to the other side.

The plunge on this side should be as close to the other side as possible. I make a light pass close to the edge bevel and check to see if I need to adjust the plunge. When the grinds meet at the same point, I begin heavier passes until I have matched the opposite side. Again, I have not addressed the point at this time, but am paying attention to the top of the grind line and that my flats are even and do not have any areas that are irregular. If you are not careful to keep the blade parallel to the platen, you can make deep cuts from the other side of the belt contacting the blade while you are paying attention to the plunge.

When you have ground the flats to match, then switch sides again and begin to fair into the point. I take my time with this, sighting from the point of the blade frequently to make sure that all lines meet in the center of the blade and that the point is not ground too thin. For this I work both sides of the blade, going back and forth until I am near finish dimension.

My rough ground blade at this point has been taken nearly to the edge flat and nearly to the top grind. It is profiles and tapers nicely to the point. I look it over carefully and make any adjustments that are necessary to balance the sides. Then I go to the disk grinder.

Disk grinder

I have mounted my disk grinder so that it is horizontal. You have to learn to grind by feel, but it doesn't throw dust in your eyes like a vertical mount does and once you get the knack of it, you have good control because you can hold the blade more securely and apply pressure more evenly. There are many types of sheet abrasive and new ones coming out all the time, but the paper that I like best is a Norton product called Adolox No-Fil and I get it from Brownell's, Inc. Brownell's is a gunsmithing supply company that carries a great many products useful to knifemakers. They are a great company to do business with and I can recommend them highly. Contact them at 1-515-623-5401 for a catalog.

I use a variety of grits from 80, 120, and 280 on the disk and will occasionally go to finer grits for polishing flats and use wet or dry for that purpose. I use 3M Spray Disk Adhesive to stick the paper to the disk and trim the excess with a knife saving a long strip for future hand sanding.

After the blade is rough ground I switch to the disk to set the flats and crisp up the lines. You can get flats flat on the disk, but you can also feather in the convex to the edge. Using a DC motor allows you to reverse the direction and slow the disk speed down for grinding after heat treatment. Most of the grinding is done off the last two inches of the disk. With the disk turning away from the edge you can grind close enough to sharpen the blade on it. Reversing direction  with the blade held in the same position, allows you to grind the top of the bevel. Tipping the blade slightly, the disk will cut on a slight convex. It makes for a wonderful tool, quiet and quick for clean up.

I go back to the belt sander to clean up the radii at the ricasso. Using a 280 J Flex belt running at slow speed, you run the belt over the edge of the platen and it will cut a nice clean arc. Use a very light touch here and becareful not the land the off side of the belt or it will cut a divot.

Handfinishing

The finish I like best on my knives is a hand rubbed finish. I do not do any more with the machines at this point, but move to the bench vise. To hold the knife securely, I use a small drill press vise with padded jaws mounted in my bench vise. I put a bar of steel 1"x15" that has a leather pad glued to it in the vise and lay the blade on top so that the blade is fully supported and the point is behind the end of the bar. This is a flexible arrangement and allows me to work on blades up to ten inches in length with good support. This is similar to the sword polishing arrangement pictured in the sword forging class notes.

There will be some slight irregularities in the surface of the blade and at the transition from the bevel to the ricasso. I clean these up and flatten the surfaces of the blade using a 320 grit red brick edm polishing stone. I use different grits of these stones and store them in small, stackable plastic trays, one for each grit. When I am ready to use the stones, I fill the trays with distilled water and a dash of Rust Lick coolant. This will keep the stones from clogging and galling the work. The Rust Lick also has an additive to inhibit rusting. You can get these supplies from MSC.

The EDM stones are friable and will break into the curve at the ricasso and clean it up quickly. Use light strokes and work diagonally to the blade in one direction. When the blade has been flattened and all previous grinding marks removed, I switch to the 600 grit stone and go over the blade at an angle 90 degrees to the previous stone. Again, light strokes, cleaning the stone frequently by rinsing in the tray water, I clean up all the previous stones scratches looking at the work from all angles in a strong light until I am sure only the 600 grit finish is showing.

Then you can switch to paper. I use 600 grit wet or dry cut into 1" strips and wrapped around a block of Corian. I wet the paper in the same solution as the stone, but held in a wider container. I use the paper lengthwise on the blade and rub with short heavy strokes to remove all of the diagonal scratches. The final passes are made with the paper wrapped around a block that has a hard rubber face. Using just the edge of the rubber, I begin at the ricasso and with a single, unbroken stroke pull the paper from ricasso to tip. I move the paper to get a fresh surface on each stroke and continue until there are no swirls or waves in the scratch pattern. This makes a good serviceable finish and is faster to do than it appears.

You can get a dramatic effect on your blades using contrast to accent the finish. Mirror polishing the swedge or mini bevels works nicely. I do this by taking those surface up to 2000 grit and polishing with Simichrome. I also like to leave a forged texture pattern on the flats of my blades for contrast giving the blades a distinctive look. The final finish is what sets a finely crafted blade apart from factory or hurried work.

Further Reading

Bob Engnath created a wonderful site with lots of information about grinding and heat treating. Bob has passed away, but the technical information is still being maintained on the web by Zoe Martin in tribute. Bob was a grinder's grinder and has made more blades than probably anyone in the business. He was open and willing to share his knowledge with anyone seriously interested.