The equipment to use for sharpening metal has historically depended on the time and place. In the 19th century, an English woodworker might choose Charney Forest stones, whereas a German woodworker might prefer a green razor hone. Japanese woodworkers (any era) valued natural waterstones from an ancient quarry, while after 1850 their US and European counterparts would seek out Arkansas stones (novaculite).
By the 1960s, top quality Arkansas stones became harder to find and second quality stones gave Arkansas stones a bad reputation. Meanwhile, the supply of natural waterstones in Japan also ran into problems, but with a contrary result: artificial waterstones, which were excellent and far less expensive, came one the market. In the past fifty years, newer technologies have also come to market.
But what is today’s woodworker supposed to use for sharpening? First of all, I should start out by acknowledging that just about everything can work. This is why you see so many different and strongly held recommendations. Some people cling to whatever effective method they first learned. But if you’re looking for new approaches, the issue is finding the right balance between various factors, including the speed of sharpening; the mess generated; the hassle of maintaining the stones; and the cost. For many people, the feel of the stone in use can also be an important consideration. In all cases you want to be able to produce a razor sharp edge that you can shave with. And I mean that literally! The right stones aren’t a magic bullet, I would say good technique is more important, but the end result of having a razor edge makes woodworking so much easier and more pleasurable. The right stones will help you get there.
You can get stones in almost any size. For woodworking, we find that an 8” long stone is the minimum size to give a comfortable stoke. A 2” wide stone will cover normal free-hand sharpening requirements with no problem. If you are using a honing guide, or want a little more comfortable experience, a wider and longer stone will be better: it gives extra room for the guide, and allows for a longer free-hand stroke as well. Longer and wider stones are more expensive than smaller stones.
Unlike length and width, stone thickness is a non-issue. Even a thin waterstone that gets manually flattened frequently will last a very long time. The only consideration with thinner stones is they might need a case to give the stone more support against breakage. But actually all stones benefit from having a case to keep them clean and prevent accidental damage.
Currently the following technologies exist for sharpening woodworking tools by hand:
Sandpaper:
You can use wet or dry paper from the hardware or auto body store for okay results. However, most stores do not stock paper in the 8000 grit range (about 1 micron) for getting a razor edge. Also typical papers are not peel and stick, which makes them harder to handle. Because of the way the paper is made, there is a wide variance between grits and the papers cut fairly slowly. On the plus side: low cost and ready availability.
I don’t know anyone who has used lapping film who would voluntarily go back to wet or dry paper. We stock lapping film in grades from 40-.3 micron. The film is carefully graded so that it cuts fast. You can use it wet with oil or water lubrication, or dry for convenience but a shorter paper life. It’s also peel-and-stick, which means you will get better and flatter adhesion, especially on the finer grits.
The main advantage of lapping film for sharpening is cost. We typically urge new woodworkers who are on the fence about sharpening to get a sample pack with the range of grits. This allows them to get super sharp tools at a low entry cost. Some people continue to use lapping film because it’s a very consistent product and gets replaced easily without having to flatten or otherwise maintain it. Also, you can cut the film into any shape and stick it onto any sharped substrate so curved profiles for carving tools, etc are easy to make. Lapping film is a great way of carrying sharpening media on the road, as it is very lightweight and doesn't take up much space.
Many years ago Fine Woodworking Magazine had an article recommending our lapping film in the 15, 5, and .3 micron sizes -- for creating a wire edge, wearing it away, and finally polishing the edge. This is a good recommendation! We also stock 1 micron paper as a polishing grit, and 40 micron as a fast cutting grit for shaping (although we much prefer grinders). Cut the film into strips and stick it onto something flat like glass. Non-stick lapping film is less expensive than the peel-and-stick type, but it is also harder to keep flat. Even with spray adhesives, non-stick film is not as flat and doesn’t offer the even coverage of the peel-and-stick. You just won’t get as much wear out of the non-stick film.
The main disadvantage of lapping film is that over time you will spend more on replacing the film than you would on just buying regular stones.
Oilstones are any stones that are typically lubricated with oil. Lubrication ensures that the abraded steel particles float off the stone instead of clogging the stone. The big advantage of oilstones is that they are hard and stay pretty flat over the years. This is especially useful for carving tools, since gouges and V tools can gouge a stone. While oilstones exist in all shapes and varieties, the most popular for sharpening are a medium india stone for coarse work, followed by a hard/translucent Arkansas stone for a razor edge. There are also fast cutting Crystolon stones, which are good in the kitchen, but are very soft and dish easily, making them a problematic option for woodworking tools. Because the stones are so hard, very small profled stones, called slipstones, are useful for carving tools.
Oilstones cut slowly and tend to be expensive. For carving tools, these disadvantages are offset by their benefits, but for other applications I prefer a faster method. Sharpening edge tools made out of A2 or D2 on oilstones will take a long time. In all cases with oilstones - except for carving tools which have different geometry - we recommend hollow grinding the tool to save sharpening time.
Modern waterstones are almost always artificial, and offer huge differences in size, cost, and performance. Natural waterstones are still available on the market, but are so expensive compared to artificial stones it’s tough to justify the purchase.
We can loosely divide the sharpening process into “shaping,” “sharpening,” and “finishing.” You will probably need one stone for each phase of the work. Shaping, where you want to remove a lot of material fast, calls for a 120 - 400 grit stone. Of the stones we stock, we find that the 220 grit Norton stone is way too soft for this work and it disks easily, and when doing rough work can easily go out of flat when working, thereby ruining the geometry of what you are working on. They are good for knives in the kitchen, but not for woodworking. The 220 grit stone by Pride Abrasives is harder, and works fast and well. This would be my pick for a coarse stone. However, because I hollow grind everything, I don’t really need one. Hollow grinding, by the way, also saves wear and tear on your waterstones.
For the basic first stone for sharpening a blade already in decent shape, I recommend a 1000 grit or 1200 grit stone. Both Norton and Pride have great candidates in this range. Other manufacturers that we do not stock, such as King, Chosea and Shapton, also make fine stones in these and other grits, and each has its own special characteristics. King is a moderately priced quality stone but it cuts a little slow. Chosera makes a great stone, but it is expensive and a little soft for my tastes. I don’t like the feel of Shaptons; I find them way too hard. Other folks swear by them. After the 1000 grit stone, I jump to a 5000 grit stone. I don’t think it matters if you jump to 4000 or 6000, but I think the jump from 1000 to a 8000 grit finishing stone is too great. It works, but you have to spend a lot more time on the finishing stone to get the same result. The main reason for skipping the 4000 grit stone is budget.
For finishing, I strongly recommend an 8000 or 10,000 grit stone. For harder stones such as Shaptons, you might want to follow the 8000 with higher grits, because with the harder stones you get less breakdown of the abrasive.
If your budget for waterstones is low, get the 1K/8K Norton combination stone. Next up would be a stand-alone 1K stone and a 4k/8/ combination stone. I use three separate stones: 1K, 5K, & 8K - individual stones to help prevent cross contamination, but this reflects more of an investment.
Waterstones, even hard ones, are friable, which means that as you use them, the binder that holds the stones together lets go, releasing the old grit particles and exposing fresh, sharp, fast cutting ones. So waterstones work quickly, but periodically you will need to flatten them. (There are a bunch of ways to do that.) Some people don’t like waterstones because they can be messy and certainly require more maintenance than oilstones.
The more friable a stone the faster it will cut on tougher steels such as A2. Norton stones are a little softer than Pride Stones, both are significantly softer than Shapton stones.
For me, the primary advantage of waterstones is feel of the stone, which can be very nice. Their primary disadvantage is that they can be messy. Water left on your tools will cause rust, and the stones usually need to be frequently flattened.
People typically don’t spend enough time with their finishing stones.Try this quick test. After you think you are done with your finishing stone, continue for another 5 minutes without adding water and see if the edge improves. I bet it will.
About 30 or so years ago, manufacturers began taking fine diamond grit, sprinkling it on a steel back, and electroplating a nickel coating over them create a diamond stone. Over the years these have gotten better and better.
We love diamond stones because they stay flat and require no real maintenance. The sharp diamond particles cut faster than any other abrasive of the same grit. The only real downside for diamonds is in the finer grits. An 8000 grit diamond stone will cut significantly deeper scratches than an 8000 waterstone. This is simply because the diamonds don’t wear as smoothly. Our solution is to use diamonds for shaping and sharpening, but then switch to an 8000 waterstone for final polishing. We also stock diamond paste which in the finer grits can be used as a polishing compound. What I don't like about diamond paste is that I don't like having stray bits of diamond paste getting on my hand. What we really like about diamond paste is that for very hard steels it makes a great stropping compound.
Click here for a series on diamond sharpening.
Ceramic stones:
Some companies make fine ceramic stones for finishing. We find these stones most useful for small carving tools, but their main advantage is low cost. We think Arkansas stones are overall better.
Leather Strops:
After finishing, we find stropping with a PLAIN leather strop gives the best edge. We use hard horse butt for our strops. In a pinch you can use any leather, but horse butt has been the traditional go to material for strops.
Carvers, on the other hand, strop continuously with a leather stop covered in stropping compound, which is a very fine abrasive. Unlike a stone, the leather has “give,” so it will conform and touch more of a carving tool than a stone would. More contact means more material removal and faster sharpening. This is a different application of the strop than using it plain as a final cleanup of a sharp edge. Click here for more information about stropping.
Click here for an article about the tools of stropping and here for to learn about the mechanics of stropping and why stropping works.
I’m going to leave our picks for honing guides for another installment.
|
Joel's Blog
Built-It Blog
Video Roundup
Classes & Events
Work Magazine