Sharpening Journey
Phil Smith
>Bill Tindall posted a note this week which started rather a good thread on tool steels and metalurgy and sharpening methods. Thought I would put up a post on how I arrived at my current state of sharpening practice with some observations of how I arrived at current state of art and science.
The photo below gives a view of an approximately 5 decade journey on learning to sharpen tools and knives. On the far right is a picture of hand driven grinder and progressing to the left ending with power grinder and diamond powder on lapping plates.
My first experience was learning to sharpen with my father in a small workshop that he used to store tools between building houses. Bevels were ground on a hand powered grinder and edges were honed on a gray oil stone. My job was to turn the hand powered grinder while he ground the bevel on his Stanley chisels and plane iron from my grandfathers plane. This is an experience that no amount of money can purchase. Link below is to a picture of dad's hand grinder and Stanley chisels. These chisels were use to literally hang hundreds of doors over an building career.
Lesson 2: My first experience on my on was with an inexpensive B&D 6 inch grinder with gray wheels for grinding and a Norton Coarse/Fine India oil stone for honing. First upgrade to this system was to a white grinding wheel. See link for picture of hardware.
While this system is capable of producing a good edge in my opinion it takes someone with real skill to produce good edges with this system. Typically the tool rest on cheap grinders is so small that it takes someone with a very good touch to reliably grind good edges. The tools I was using were all of carbon steel which means that overheating the edge is very easy to do. In addition the irons on the inexpensive Stanley plane is so thin that it is difficult to hand lap the bevel consistently. It is no wonder that some woodworkers give up on sharpening if they start here.
Lesson 3: About a decade ago based on article I had seen in woodworking magazines and on our clubs experience I switched to using sandpaper on glass. With this system you can consistently produce good edges on the commonly available woodworking tools. By using coarse sandpaper to replace the grinder you remove the risk of burning the tool on a high speed grinder. However it takes very good technique to go through the series of grits by hand. I jig for holding the tool at a set bevel is essential to get good edges. Link below is to setup that I used for several years. By this time I had moved to planes with thicker and better irons that the big box specials that I had started with. However the chisels were still of the chrome/vanadium variety and while they would take a good edge, did not hold that edge in oak and other hardwoods. Edge was too soft and easy to deform in use.
Lesson 3: Based on my experience with chrome/vanadium chisels I treated myself to a small set of Japanese chisels, complete with water stone and Maketia grinder for my 50th birthday. The chisels take a very good edge and solved the soft edge problem that I had seen with my previous chisels. However I now found that although the chisels did not deform they were fairly easy to chip. Now have two ways to put on good edge. Link below is to setup for water stones.
Lesson 4: Move to tool steel and diamond lapping. A few years ago there were numerous post on badger pond about the inability of tool steels to take a good edge. Based on my own experience with oil stones and water stones that is indeed the case. With M2 you can literally lap and edge till the cows come home and not take enough metal away to get a good edge. Bill and I started working with M2. He was looking for a chisel that would hold an edge while chopping mortise and dovetails. We found that indeed M2 would take a good edge when sharpened with with silicon carbide on glass but the steel was too brittle to make a good chisel. Poking around on the internet we found that there were indeed tool steels that were advertised to be much tougher that M2 at a hardness over RC 60. Looked like for a couple hundred dollars we could run and experiment to make some paring chisels, mortise chisels and a couple of plane irons for wooden planes. We started with CPM 3V because we were looking for a very tough steel to make a very good mortise chisels. We were looking for a steel that you could driver into wood without deforming and yet not chip when chips were pried out. Made the other tools simply because we had the metal and it was a cheap experiment. Made the tools but now had a new problem. Yes the tools will take a pretty good edge with silicon carbide paper on glass they really killed the papers useful life. Tools are now tool abrasion resistant for our sharpening media. As many have noted in the post below the steel and sharpening media must be matched. Looking on the internet again found that loose diamond is available and widely used in the metal working industry, among others. Based on our experience with sandpaper on glass we assumed that we would need complete series of diamond plates to get a good edge. I made a complete series of cast iron plates stating with 30 micron and going down to 1 micron. You can see these on the left in the picture at the end of this note. However we have found that diamond is so much more aggressive than the normally used abrasives that you need dramatically fewer steps. Below is a picture of my current sharpening setup. What you see is an cheap 8" grinder with a fine and coarse very soft ruby grinding wheels. The grinder is equipped with One Way tool rest. Good tool rest are essential for consistently grinding a straight even bevel. A cast iron plate with 1 micron diamond powder, bevel gauge for setting the bevel, square for ensuring a square edge and a cheap loop for looking at the edge. I grind until I have a wire edge on the bevel and then lap the edge with 1 micron diamond powder on the plate. When you have a bright bevel along the edge you are sharp enough for most uses. Some may prefer to go to 1/4 micron but 1 micron will meet most woodworkers needs. Below is a picture of the tools. Tools include complete set of paring and mortise chisels out of CPM 3V, and a couple of plane irons out of CPM 3V plus a couple out of CPM particle M4. Now that I have made the journey to tool steels I will not go back to to the O1 and A2 tools for several reasons. 1. In my opinion they are simply easier to grind than the other tools if you use the right hardware. These steels temper at around 1000 F. That means that someone with relatively low skill can grind them on a grinder without worry of burning the edge. This is a big deal for new woodworkers. 2. They take a good edge when sharpened with diamond powder. 3. They perform. Steve Elliott has shown that the 3V has a useful life of about 2X over regular plane irons. That is a big deal in my opinion, and I think that there is room for more with with M4 or one of the other steels. Below is link to picture of a CPM 3V mortise chisel sharpened to 26 degrees with a 7 inch wheel. The effective angle at the tip is more like 23 to 24 degrees. In use I use this chisel with 2 lb dead blow mallet to cut mortise in oak. I use Bill's and others method of drilling a hole at one end and then drive the chisel essentially full depth. By about the 2nd or 3rd chop I am at full depth prying out chips. I think this would be difficult with either a A2 or Japanese chisel ground at this steep angle. The steep angle on the chisel makes mortise easy to start and the chisel easy to drive for the following chops.
