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Sharpening – Do I need to go to 30,000 grit?

Posted by is9582 on March 2, 2012 with No Commentsas , , , , , , , , , , , , , , , ,

Like many of you, I sharpen on a very regular basis. I’ve tried most of the different sharpening media that is presently available, along with some that are not so readily found any longer. I’ll share some of the results, and hopefully answer the title question.

When I first got into woodworking, I purchased three King water stones in grits up to 6000. I had decent results, but the lower grit stones dished so quickly that it seemed like I was spending too much time trying to keep them flat. At that point, I didn’t have any diamond stones, with which to quickly flatten the water stones.

Later on, I bought a WorkSharp 3000, thinking it would not only sharpen, but provide rapid repeatable results. Another of the major selling points for me, was the ability to flatten the backs of old chisels, without spending hours at a stone. The highest grit was again 6000. One thing I noticed that seemed to be even more important for the finest grit sheet, was laying the sheet completely flat. Since the grit size is so small, on the fine sheets, a small bubble or leftover residue on the plate can cause uneven honing. One accessory they added, after I “parked” my WorkSharp, is the leather honing wheel. I have not tried this option, but it may offer some of what I perceive as the missing precision, at the final honing process. One caveat to know, is leather will compress, which may not sound like a problem. Depending on the thickness of the leather, the amount of compression can vary, and cause some unwanted results. One such negative result would be a slight rounding over of the tool edge. This may not show itself, until your next sharpening. Put some black marker on the surface you wish to check, out to the very edge. Work the tool in the normal manner, at the grit at which you normally start. After a quick touch to the media, check to see if any of the marker remains, at the very edge. If it does, this indicates the very edge has at minimum, a slight rounding. Since I haven’t personally played with their leather honing wheel, I can’t advise as to its compression factor, but a light touch is suggested. The WorkSharp, in my configuration, provided decent results.

The next sharpening system I purchased was a Tormek T-7. One of the selling points for this system, is it has a large number of accessories that make it possible to sharpen almost anything. For my needs, that part was overkill, since I primarily wanted to quickly and easily sharpen my chisels and plane irons. The T-7’s sharpening wheel has a grit size of 220, which using the provided stone grader, can be modified to act as a 1000 grit. It works well, but as you might imagine, even after going to it’s leather stropping wheel, the tool sharpened was no where near a 6000 grit sharpness. On tools such as turning gouges and the like, the level of sharpness from the T-7 was certainly adequate. Tormek has additional sharpening wheels, of which, one is a 4000 grit Japanese stone. I have not tried this stone, but it is still an option, for those wishing a finer edge, while still using the Tormek. For optimal results, chisels and plane irons still needed, at minimum, some light attention on an 8000 grit stone.

I own both Norton 220/1000 & 4000/8000 water stones, as well as Shapton Glass stones in 1000 & 16000 grits. The Norton stones have a medium matrix, so they both provide new abrasive regularly, but it’s strong enough that they don’t dish as quickly as the King stones. Even with this said, I flatten these stones either between each tool, or after a minute or two of use. This may sound compulsive, but it’s what is required to know you are not unintentionally adding shape to an edge. The Shapton Glass stone series is a ceramic matrix that is quite a bit stronger than the Norton’s matrix. With this, they dish much less quickly, while still sharpening quite rapidly. I still flatten these regularly, but I can probably work a bit longer, before it’s needed. Since they sharpen quickly, it’s unusual to spend more time on a stone, than it can stay flat, other than potentially the 1000 stone. While I don’t use the Shapton stones as regularly, I keep them for sharpening non-flat items such as carving tools. The harder matrix helps them hold up to the tough contact of this type of tool, much better than a softer stone. Both Norton and Shapton water stones, at these grits, provide an extremely sharp tool that I can trust to be razor sharp.

Ok, ok, I haven’t mentioned anything in my kit that is close to a 30000 grit. How can I try to compare tools sharpened via these stones/devices to a tool at 30000 grit, if I don’t actually have a 30000 grit stone? Yeah, that wouldn’t be cool. As it happens, I do actually have a couple of natural Japanese water stones, that are each in the 25000 – 35000 grit range. I have tested both American and German made tool steels as well as Japanese tool steels on these stones. Can I tell the difference? Hmmm, that’s a good question. I really don’t think I can tell much difference in the non-Japanese tools. Once something is razor sharp (e.g. reaching the 8000 grit range), it’s exceedingly hard to feel much difference in the way it interacts with wood, at higher grits. On my best Japanese chisels, I can tell the sharpness is enhanced, even though it isn’t hugely different, as you might find moving from 6000 to 8000 grits. Beyond the sharpening aspect, the natural Japanese water stones leave a different finish on the tools. This is most noticeable on the laminated Japanese tools, although still viewable on almost all tools. With the laminated tools, these water stones leave a different finish on the hardened steel compared to the soft iron. The hardened steel looks almost like a cold mirror, that someone has breathed on, leaving the foggy myst. This is much more pronounced than when sharpening these laminated tools on other stones. Other tools will also take on this non-shiny texture, and strangely, it is still amazingly sharp.

Many people look at a tool’s edge, and if sharp, expect to see a mirrored type of reflection. Just a reminder that shiny does not always equal sharp, especially if the sharpener did not hone at an angle sufficient to reach the very edge. When you sharpen, make sure you raise a burr on the opposite side, so you know you’ve actually reached the edge. Otherwise you may just make something shiny.

Is it necessary to sharpen a tool to 30000 grit? For me, no, but this seems like a more personal question. I think as long as you sharpen to 8000 grit, as a minimum, you’ll have tools that make woodworking what it’s suppose to be. FUN! Go make some shavings.

When is Cherry not Cherry?

Posted by is9582 on February 16, 2012 with No Commentsas , , , , , , , , , , , , ,

I was reminded the other day, how selection of wood for dovetailed boxes, can make or break the project. I’m sure this initially seems like I’m only talking about aesthetics, but in actuality, the physical characteristics are at least as much of concern. A man brought me a piece of wood whose species was not immediately apparent. From the coloration, weight and relative hardness, it felt like Brazilian Cherry. He was having a really rough time cleaning up the board without significant tear out, even using a high-angle of attack. We worked on it with multiple planes, and ultimately found a scraper plane worked well. I had a different scenario with the Brazilian Cherry I’d purchased.

A number of years ago, I bought a board labeled Brazilian Cherry, since I thought it would compliment some Maple or other light colored wood, in a hand-cut dovetailed box. Many times I will use some good contrast in my dovetailed boxes, which is usually pleasing to the eye. The board I purchased was already surfaced on four sides, and was very flat. I cut the lengths I needed, on my tablesaw, which gave me no idea just what I was up against. I cut the tails on the Maple boards, and laid out the pins on the Brazilian Cherry. I sawed the pins, as usual, and didn’t really notice much difference. Same thing when I removed the majority of excess wood, with my coping saw. It was only when I shifted over to my chisels, that this wood reared it’s head. As usual, I made sure I was working carefully, so I didn’t try to hog off too much wood in each pass, and potentially risk diving below the scribe line. I noticed fairly quickly that my chisel was acting strange; almost as if it was already dull. I looked at the edge of the chisel, and it was amazingly dull, and had chipped as well. I re-sharpened my chisel, thinking it had probably started to get dull on the previous job, and I hadn’t noticed. OK, now this baby is sharp. Back to the board. I know this is likely fairly obvious, but in very short order, I was headed back to the sharpening stones. I’m not sure how many times this went on, but I finally decided to shift to another chisel. This time I picked up a Japanese chisel I bought while in Japan in 2001. This chisel had really shown me just how long it would retain it’s sharpness and also it’s fine cutting edge. I started removing wood, and at first it was doing great. Well, this didn’t last. I finished one end of one of the two pin boards, and thats when I set the Brazilian Cherry board aside. It felt like I was going to use up a chisel or two, just in the amount of sharpening required, and this was on a small box. I milled up some regular Cherry, and finished up the pins on these boards, finalizing the box fairly rapidly.

I’m sure I might find another usage for Brazilian Cherry, in the future, but let this remind you to assess each wood’s attributes before buying in large quantity. This instance was not too bad, since I only bought one fairly smallish board of the Brazilian Cherry, to test for this box. What if I’d been making a chest of drawers, with lots of dovetails, or something else with similar design. I’d ultimately have had a bunch of wood sitting around, waiting for a project in which it would behave.