Rich Hale Knife Finishing

[Glenn]

IForgeIron Blueprints
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BP0235 Knife Finishing
by Rich Hale
 

Several have asked how can they get a clean mirror polish on a knife blade. I can show you what I do, Keep in mind that I use Stainless steel that has been heat treated and cryogenically treated. I use one of three steels, ATS-34, 440C, or 154cm. None of them are very different from the other and they all worked about the same with the methods I use to finish.

The belts I use are 50grit, 220grit, A45, and A16. All of the belts are made by 3M. When I order I rarely remember to look up the catalog numbers so I order a 50grit yellow belt. 220 grit red belt. The other two belts are structured abrasives they call trizac belts.

The grit is not natural as in the first two but each little piece is pyramid shaped and arranged in rows. Compared to abrasives that may be more familiar to you; an A45 is about the same as a 400grit, an A16 about like a 1200 grit.

One of the keys to getting a smooth consistent grind on a blade is to apply even pressure to the blade as it is held against the grinding wheel. For even pressure I use a push stick. I make these from scrap wood. Note the ledge at the bottom of the surface that goes against the blade.

Note that the upper and lower edge of the stick is against the blade and the bottom of the blade sits on the ledge. This is a big factor in control of the grind.

The wheel is at the correct height for me. The push stick has the blade held firmly and my knees have enough bend to allow my body to move from side to side as I grind the blade. Hands are against my belly and they stay there, and movement is with whole body. If my hands get away from my belly I will lose control of the blade and cannot keep the lines correct.

Now lets take a look at the blade as it is ground with the four different belts.

I leave all of my blades a little on the thick side so I can flatten out any warping during the heat treat, this also helps to eliminate the warping. All blades are rough ground prior to heat treat with a 50 grit belt. When they return, and I am ready to grind them I use a used (old) 50 grit belt. The new ones are a bit to sharp for this task.

My goal with this belt is to establish all the lines. Both grinds should start at the same place on each side of the blade and the top line of the hollow grind should be the same across the top and end at the same place on each side of the blade.

This shows the blade after grinding with a used 220 belt. I have put a little arrow to show a place that has scratches left by the 50 grit that I have not removed yet with the 220. I MUST remove these before changing belts.

This shows the blade after grinding with the A45. and it also shows 50grit scratches I did not clean up with the 220. I have to step back to the 220 to remove the scratches or they will show forever. Before changing to a finer grit belt examine the blade under good light and look at it from several angles. The grind should be consistent with no deep lines.

Look at this blade close and you will see a nice grind with even lines except for the same problems as in other pictures. There are scratches in the same area, only these are not as deep and were created by the A45. These will come out with more work with the A16. Now recheck the blade on both sides.

I hope you have noted that for all of the work with the belt grinder I have held the blade with the edge up and used the push stick. Keeping my hands firm to my belly and moved side to side for the grind. When you are sure you have all the lines correct, all the scratches removed and the blade is a nice satin finish from the A16, it is time to hit the buffer.

For the buffing I will work without the push stick, but with my hands on my belly as before which gives the best control. Keep your knees bent a bit once again for movement. I will also be buffing with the edge down. I only put the part of the blade against the wheel that is on the floor side of the blade. For the upper part of the blade I turn the blade and work once again towards the floor on the part of the blade nearest the floor. You do not want the buff to come over the top edge of the blade as you work, it will try and remove the blade from your hands.

This is one of the buffers I use. Double ended with 1750 rpm. I have stacked on top of it the two buffing compounds that work for me. The green is matchless green and is the coarser of the two. The small one on top is no scratch pink for a final gloss. I use 8 inch loose muslin buffs for both compounds and I do not switch from one to the other. If I apply the green to a buff I always stick with green.

The steps I took earlier with the belts, sets up the whole buffing process. For a blade of about four inches, I can buff both sides with the green buffing compound, step to the other wheel for the pink buffing compound and finish up in less than 3 or 4 minutes. If you find scratches the do not come out right away with the green buffing compound, return to the grinder and try an A16. Examine closely and if they are gone go back to the buff. If they are still there try an A45 then A16. When all scratches are gone and the blade has a nice shine hit it with the pink. That really makes it right.

The biggest key to a superior finish is in the quality control that you do. If you examine any blade under a microscope you will find lines, so small that they cannot be seen by a naked eye. The lines will be even spaced and even depth. Any lines are not parallel or deeper than the rest they stick out like a mistake. Yes, even small lines that are not like the rest show up with normal vision.

Do you want to, or need to put a mirror polish on your blades? That is your call. These methods not only apply to blades, but they may work on anything you make or restore. It does not have to be stainless, but will work on anything you want to polish including natural or man-made handle materials.

Buffing compounds

Choose what you put on the wheel carefully. Some of the black emery compounds are about 400 grit. If you go as fine as an A16, remember it is around 1200 grit, and you will put in scratches with the buffer and a 400 grit compound. Match the grit of the belts and the grade of compound with the finish you desire.

I believe some knife blades look really nice with a finish done with 220 grit belts. However it will suffer if you buff it with the fine compounds I use, as it will get blotchy and uneven. An A45 gives a nice shine with out the high polish and looks really nice. A compound around 600grit would work well with that I think but have not tried it. Try what you have in the shop and see what works, and what fails.

I use the same series of belts and a smaller buffing wheel for handle work. I think the buffing wheel is around 4" or so, but is an old one worn down. I use a fine white compound on the that wheel. The small size reduces speed and the white does not stain the material.

This last picture is an example of what I like in a blade finish.

Keep in mind the same principles if you want a flat grind or convex ground profile.

You can finish a blade with similar grits of wet or dry sanding paper wrapped over a flat metal piece. Work within the guidelines above and get the finish you like. Keep the paper wet as you work. A touch of dish soap in the water will keep the grit from clogging the paper. And if you are working with high carbon steel wipe it dry of water when you are not working on it. Carbon steel will rust right before your eyes if you let it, especially with the coarser grades of paper.

The knife is ATS-34 ss with 416 ss bolsters that I engraved. Wood I think is maple burl that has been stabilized. The block was unmarked when I bought it.

The Bowie is also ATS-34 with steel guard and but cap that have been blued and the guard has a nickel inlay. The handle is real sambar stag. This knife has been sold and will be delivered this week. The sheath is old style Mexican single loop of Latino leather.