We shared a brief preview of Del Corsi’s Mirror Finishing article from our July 2022 issue a couple of weeks ago. Del also sent us a few video clips which our Graphic Artist Katie compiled into a Youtube video which is embedded at the bottom of this piece.
Mirror Finishing -By Del Corsi
One of the most spectacular looks on a knife blade is a well-done mirror finish. For some reason we are really attracted to bright, shiny things that produce reflections. A mirror is never very far away. When it comes to knives, a mirror finish done well is a thing of beauty – but poorly done, it highlights every blemish. I read somewhere that the first man-made mirrors were made of polished stone such as black volcanic glass obsidian. I know that obsidian makes a terrific knife or tool, it has an exquisite shine as well. Is it possible that these were the first mirror finished knives?
Personally, I love the look of highly polished blades, and especially relish the challenge of bringing a knife to a high-level finish. I am eager to provide a look into a few methods used to achieve this type of finish. This could simply be a how-to story on a few different ways to polish a blade, but it is so much more. Don’t get me wrong, there will be a wealth of basic and next level information for those interested in learning how to accomplish, or perfect the process. The goal is to showcase two very different methods of achieving a polished finish, but another aspect is to highlight the artistic nature of this process. While there is no chrome plating involved, as you will see, we do use a whack of green chrome polishing compound!
My introduction to custom knives came through the loss of a treasured knife while out hunting. A friend told me about a local custom knifemaker named Steve Price. So cool how a misfortune or loss can result in a life changing event! I called Price and was invited to check out his work. A beautiful drop-point hunter with a spectacular mirror finish was soon on my belt. It was mind-boggling that someone could make such a beautiful knife by hand. A friendship developed, leading to many days in Steve’s shop learning how to make knives. His signature finish was the mirror, with D2 as the preferred steel. D2 steel can be very difficult to polish, too much heat when buffing this steel can cause an orange peel effect on the blade. This is the poor finish I mentioned above!
My time in Price’s shop was during the early 1990s. I learned from him about a knifemaker from Manti, Utah who had popularized a cork belt polishing technique Price used. Steve “SRJ” Johnson was that legendary knifemaker, he was using the cork belt as an extremely effective polishing tool. Fast forward to the present and SRJ is still doing magic with that technique. Just last year I learned of another technique for polishing blades, we could call this a “New School” method. Knifemaker Todd Begg has helped to popularize this procedure. He uses polishing stones and diamond paste to produce an outstanding mirror finish. Anyone who has ever seen one of Todd Begg’s signature blades knows what a high-level finish looks like. Both Begg and SRJ have flawless knives, and I am grateful to them for allowing me to share some of their knifemaking expertise.
Steve Johnson’s Cork Belt Polishing Method – Old School!
Steve used to moderate and post information, along with suggestions and tips, on an online forum. At one point he went into length detailing his blade polishing process saying, “After heat treat and following a somewhat broken-in 400 grit Trizact aluminum oxide belt. I start by using a 400-grit cork belt that has been “broken in,” going over and removing the scratches from the previous 60-grit belt.” He recommends using, “A fair amount of SS 300 White Rouge buffing compound. You can push pretty hard, but don’t peel the abrasive & cork from the belt.”
Next, he uses 600-grit and/or 800-grit cork belts, either one will do, also broken in, and loaded with white rouge. Following this he does the final buffing step. Once again, the white rouge is used on the buffing machine. His experience has shown that, “The blade polishes in less than one- or two-minutes time.” Anyone wanting to utilize the cork belts should really heed this next advice from Steve, it cannot be understated. From my own experience, many knifemakers do not achieve the “broken in” stage on the cork belt, so they quickly abandon this method. If you follow Steve Johnson’s advice, there will be a welcome new tool in your quiver. Steve was very grateful to learn information about this belt, which he received from T. J. Yancey, in Estes Park, Colorado, back in the late 1970s. Steve explains this critical step in detail; “To break in the cork belts, put them on the grinder, with a tool rest in place, using a smooth wheel, if you have one. If your wheel is serrated, you’ll want to apply a somewhat lighter pressure. Using a scrap piece of 3/16”-1/4” blade steel, or whatever, wear on that belt for a good 10 minutes. Be careful not to “break” the corners, or edges, of the belt too aggressively, or the cork and polishing medium can peel off. Buffing compound helps a lot, I think, in making it easier to “fold” around the edge of the wheel a little. You do need to slightly break, or round the corners/edges of the belt around the edge of the wheel, however, be careful not to overdo it. This process is smelly and dirty, for that 10 min, but it takes that long (10 min. by the clock) to break the belt in. When you think it is ready, go ahead and try it on a blade. If you don’t get a nice finish, it might take a little more break-in.” Anyone wanting more information is welcome to message Steve Johnson on his Instagram account – @srjknivessrj.
Todd Begg’s Diamond Paste/Polishing Stones Method – New School!
The process Todd Begg chooses is like going on a spiritual journey, at least it appeared this way to me just from using the diamond paste on a few blades. It was reinforced when he explained his process. Todd does not use a buffer to polish his blades, though he does “briefly use a Dremel with a felt polishing tip to lightly final finish.” I am quoting from a January 2021 Knife Magazine story in which I asked Todd about his process. The next comment was, “I want clear, crisp grind lines.” He certainly succeeds!
Todd first learned about mirror finishing when he trained and worked as a machinist; this alone speaks volumes for his expert finishing skills. I love hearing him explain how his method continually “sharpens grind lines.” As I also mentioned in Todd’s Knife Magazine article, he first noticed that, “Polished surfaces of injection molds showed a high level of mirror finish.” He also noticed that these finishes were measurable and provable, such as an A1 or A3 finish.
After the 220-grit or 400-grit stage on his belt grinder, he goes to diemaker stones beginning with 400 grit. Begg again stresses that this technique is, “Constantly sharpening the grind lines.” The next step is taking postage size pieces of sandpaper that are used on the bottom of the diemaker stones. The diamond pastes are then used up to that signature ½ micron finish he is famous for. And yes, the grind lines on the final finish look sharp enough to draw blood! Todd can spend an entire week polishing one folder blade.
It quickly becomes clear why Begg doesn’t use a buffer to polish his blades, buffing can tend to wash out your grind lines somewhat. That is, unless you are Steve Johnson! His grind lines and finishing work are perfection, his comment above of one- or two-minutes polishing time speaks volumes, he doesn’t wash any lines out! This is a good time to mention that the buffing machine is one of the most dangerous machines in a knife shop. I run an 1800 RPM machine but starting out I used a 3400 RPM unit that got the adrenaline running. Buffing wheels are well known for grabbing a handheld blade and transforming it into a deadly projectile. It happens so fast, in the blink of an eye!
This is a great segue into my method of polishing blades. As mentioned above, the knifemaker I learned from provided a mirror polished blade as his primary finish on knives. Learning from knifemaker Steve Price was great, he was an incredible craftsman and Knifemakers’ Guild member. My goal early on was to somehow produce a mirror finish as good as, if not better than my mentor. I have little skill or natural talent, but my desire to make a good knife and reach for this goal made up for that. I’d like to say to every knifemaker reading this, don’t ever quit reaching! It is doubtful that I ever succeeded, but the journey is more about reaching, which means lots of hard work and determination. My feel is with this approach, the goal is already achieved.
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