This phenomenal video of a microscopic view of what happens when a plane blade cuts wood was created by Professor Yasunori Kawai and Honorary Professor Chutaro Kato at Yamagata University, as part of their research in the role of cap irons in planing. This segment shows a plane blade without a cap iron, planing with the grain, then against the grain, and finally taking a thinner shaving against the grain.
The captions in the video are mine, and are my take on what I am seeing in the video. I will fully admit that I don’t know Japanese at all, and so the captions should in no way be taken as a translation of the text seen in the video. In fact, I may be completely off in my comments compared to what the text says.
(Thanks to Bill Tindall for tracking this video down.)
Source: kegaki.kj.yamagata-u.ac.jp
Q:hey, i have build a traditional sumitabu. the first run was great but the ink got dried and jamed the whole thing. do you know how maintain this tool?
Anonymous
I have a sumitsubo, but haven’t played with it too much. A sumitsubo is an ink pot where the ink reservoir has a wad of raw silk. There’s also a wheel and a string that passes through the silk with a pin on the end. It’s used in two ways: either as an ink pot by dipping a stylus called a sumisashi in the ink held by the silk, or by anchoring the pin at one end of the line you want to mark, pulling the string through the ink-soaked cotton, and using the string much like you would a chalk line.
The ink is usually water soluble, so I have a hard time figuring out how you could jam your sumitsubo. Maybe adding some water to reactivate the ink will help loosen things up. And I would love to see a photo of your sumitsubo. Good luck.
SawStop and Swiss on rye
It’s Safety Week again. Among woodworkers, there’s probably no more volatile subject when it comes to safety than SawStop. And there’s probably no one more unqualified to talk about table saws than myself, since I have very little experience using one, and I don’t even have a table saw in my shop.
On the other hand, I do know a lot about safety procedures. In my day job, I’m a pediatric oncologist, and one of my responsibilities is to give chemotherapy to kids safely. As you might guess, this is a process where the results could be disastrous if a mistake occurs. It’s in this context that there is a lot of misinformation about SawStop technology.
Now, in this discussion I do not want to talk about nor do I care about the politics of SawStop. Here I am only addressing one thing: does SawStop make using a table saw safer?
A common comment that is made about SawStop is that having a safety device that prevents major damage from contacting the blade with a part of your body will make the user less vigilant, leading to more injuries, and that nothing can take the place of paying attention to what you are doing, which is enough for safe practice. This is a nice philosophy, with only one problem. No one who actually works with safety protocols believes this to be true.
The reason for this is the Swiss Cheese model, first developed by James T. Reason, a British psychologist, in 1990. This model is used to analyze procedures to see if they are safe, where they can be improved, and in the case of accidents, how they might have occurred despite existing safeguards.
In this model, slices of Swiss cheese are our defenses against an accident occurring. The holes in the cheese represent ways that an accident might get past each slice. For a woodworker in his shop making a cut on a table saw, one slice of cheese might represent his concentration as to what’s going on, another represents shop conditions, a third represents how well behaved the board is, the fourth is SawStop technology, and so on. If there are enough slices of cheese, and if the holes in the cheese are small enough, then the arrow might get through some layers, but will be blocked from passing through by another layer.
An accident happens when the holes happen to line up. Here the model turns a little surreal, because the holes are not fixed in position. Rather, they change size and move around over time. For example, over time the lighting in the shop gets worse as your fluorescent bulbs get older, or it gets messier as you get into your project. So the holes in that slice of cheese get a little bigger over time. You may decide it’s not worth putting the riving knife back for just one cut, so the holes in that slice get bigger as well. If you have a beer in your shop and then get back to work, more holes get bigger. Or maybe you decide to do one last thing late at night, when you’re tired. Bigger holes.
There’s no doubt that SawStop’s particular slice must have a very small hole in it. The data is not completely clear, but Highland Woodworking issued a press release in 2009 that over 600 cases of fingers were saved thanks to SawStop. There has never been a contact where SawStop failed to mitigate the damage that could have been done. And the fact remains that whatever the size of the hole in the SawStop slice of Swiss cheese, that hole is quite independent of the state of mind of the woodworker.
At work, we work very hard to try to eliminate the chance of a chemotherapy error happening to a kid by putting multiple layers of checks in the process. I have to write for the chemotherapy. The pharmacy double checks my dosing, my math, and the treatment plan for the kid. The nurses administering the chemotherapy also double-check these factors, and two nurses have to agree things are right before giving the chemo to the kid. The idea that we should prevent chemotherapy errors from happening by solely relying on the vigilance of the doctor is ludicrous. And I can promise that none of us in this process take our roles any less seriously because we know that other people are checking the chemo as well.
We’re not the only ones who use this model of safety. Airline pilots, firefighters, and nuclear power plants all use this approach. And there’s no reason why it can’t be applied to our shops as well.
This is why arguments like, “We don’t need SawStop technology because woodworkers being a little more prudent will fill the same role” simply are not credible. Prudence doesn’t fill the same role as flesh sensing technology. Neither do riving knives, better designed guards, or other alternatives that have been proposed. Flesh sensing technology has one job to do: prevent severe injury if a part of your body touches the blade. This is completely separate from the awareness of the woodworker. At that point, you’ve already gotten past all the other layers of cheese, including the personal awareness slice, so it will be a very good thing if it’s there. To say that you don’t need flesh sensing technology to be safe, now that the technology exists, is to say that we can remove a slice of Swiss cheese and be as safe as we were before. Again, that argument doesn’t hold water.
SawStop technology is sometimes criticized that it won’t prevent kickback. But it still is an additional layer for injuries due to blade contact. And it’s worth noting that SawStop table saws have always had riving knives, not splitters, as part of their standard equipment since 2004 — several years before the other manufacturers came on board.
Now, there are many reasons why a woodworker might not want to buy a SawStop table saw. If you don’t want to buy a SawStop because you don’t like the politics surrounding SawStop, that’s fine. And if you don’t have safety features high on your priority list for deciding on a tool purchase, that’s fine as well. But deciding not to purchase a SawStop because somehow it’s not really safer makes no sense at all.
Tapping Out a Western Plane Blade
Japanese and western woodworking tools have nothing in common.
Sentayehu Teshale is a woodworker in Addis Ababa:
As long as my chairs last, my customers will remember me.
Not once does he mention the obvious aspect of his woodworking.
(Via Robin Wood.)
Japanese plane five ways
Most Japanese planes have some sort of western counterpart. There are Japanese versions of smoothing planes, jointers, plow planes, chamfer planes, and so on. This is a Japanese plane that really doesn’t have a western equivalent. It’s called a gotoku kanna, or five purpose plane, according to the translations I have read.
The plane has a body that looks like an inverted T, and the blade runs across the width of the plane.
This plane gets its name from the fact that it can serve five purposes: left sided rabbet plane, right-sided rabbet plane, left grooving plane, right grooving plane, and a smoother, as can be seen in the following pictures.
The gotoku kanna does an admirable job in four out of the five functions. It cleans rabbets and trims side walls of rabbets and grooves on the left and right very nicely. But as a smoother, well, it really kind of sucks. As the plane takes a shaving, there really isn’t anywhere for the shaving to go, as it gets caught up under the middle of the plane. The shaving gets jammed up, and it’s a pain to get it out.
Four out of five makes it a B-minus student, or, one grade below an Asian F. But I have to admire the gizmosity factor in combining all of these functions into one plane.
Making Kumiko
The first in a series of really nice write-ups on making kumiko by Geremy Coy, a furniture maker in Washington, D.C. It looks like he’s using western tools, which makes me feel less bad about using Japanese tools to make western woodworking projects.
Building a Roubo workbench rerun - 6
(Originally written Jan 26-29, 2009)
I was thinking about working on the legs for my workbench, and realized that I had made a tactical error. This bench is going to be a Roubo, and I was planning on using 4x4s for the legs, which would wind up being slightly less than 3-1/2” sqaure. Problem is, the plans I’m working from call for legs that are 5” square. At first I thought, “Who cares if the leg is 5” or 3-1/2 inches square?” and so I would just use the 4x4s as they were.
Except that I then realized last night that for this bench design, in addition to providing support, the legs also make up clamping surfaces, and I’d go from a leg vice that’s 5 inches in width to a leg vice that’s 3 1/2” or less in width. I don’t think that the leg thickness matters that much for the sturdiness of the bench, but I can see how clamping would benefit from a wider surface.
The cheap and easy way out of this is to just glue a wider board on the front of the 4x4s, sort of like a T shape, but it’s my bench, and I’ll have to look at it. So 5” legs it is.
I came come up with a variety of ways to do the glue up, which are in the picture. They all seem to have some pros and cons.
A would result in the neatest appearing leg, but I don’t know if I have to worry about the leg splitting over time with movement if I encase the 4x4 on all sides.
B allows me to use the 4x4 stock that I have on hand without having to go buy wider boards. It’s also the ugliest.
C would be a little easier than A, and still has a relatively neat appearance. I’d have to go buy additional wider 8/4 material to do this.
D is the easiest to do, but I’d have to go buy even more additional wider 8/4 material than in option C to do this.
Myself, I’m leaning towards A. I know I won’t mind the extra gluing steps, and as I said, it will be the neatest appearing out of them all.
========
After further consideration, I came to my senses. Actually, it wasn’t really me that came to my senses. It was Steve Altman, an incredible woodworker who makes amazing boxes, and who is also a fellow member of the Central Jersey Woodworkers Association, the woodworking club I belong to. He sent me a note that I’ve lost, much to my chagrin, but it said something like this:
Make a proper leg, and do it the right way. This is your workbench. This is a tool that you will use every single time you go into your shop. And you’re trying to save on what, $15-20 of construction lumber? You’re going to blow away that amount of money in scrap wood on the next project you make out of any decent quality lumber. So do it right.
I stopped by the borg on the way home, and found a couple of 2x12s that I milled up and laminated together for making 5” square laminated legs, which can be seen in the top photo. That was the best $20 I ever spent.
