the Carpentry Way: Two on Test (Part 3)                                                          

Two on Test (Part 3)

    
Continuing on then with this look at a pair of Japanese bench chisels I am setting up and will test out. These chisels are made by two makers in Niigata Prefecture, and the brands are Yamahiro and Kunitoshi. Neither brand is sold much outside of Japan as far as I am aware, so I am pleased to have the opportunity to bring these two fine tools to the attention of a larger audience.

In the previous post I stripped the protective coating of lacquer and removed the striking rings, kashira, from both chisels. Today I want to illustrate how I fit those rings back onto the chisels. As noted earlier, Japanese chisels do not come ready for use out of the box, and will require a certain degree of set up before use.

for re-setting the striking ring, you need a solid work surface, a block of wood, a hammer, and, ideally, a ring setting tool:


The inside of the ring setting tool is conical, so that it can be driven directly against the striking ring without getting hung up on the wooden handle:


If you don't have a ring setting tool, it is usually no problem to find something that will work acceptable, like a socket, piece of pipe, etc.

The ring checked to make sure its inside portion is smooth. If there are burrs or such things, a file is taken to the ring to clean up the surface. In the case of the Yamahiro, the kashira required no fiddling at all. The ring is slid onto the top of the handle. Ideally you want that ring to slide on by hand until it is about 1~2mm proud of the top of the handle.

The Yamahiro had a fit of ring to handle that was fine in that regard. The ring setting tool is then placed on top in preparation for seating:


Be sure that the blade of the chisel is set cross-grain on the block.

A couple of moderate hammer blows should drive the ring down until it is 1~1.5mm below the end of the handle:


[EDIT] D. Young made a good point in his comment below that if the chisel is likely to be struck hard, as a timber chisel, say, then you want to be on the side of having a bit more wood on top, say 2mm.

If the striking ring will not slide onto the handle far enough, then one takes the end and places it atop a suitable 'anvil' (here, I use the edge of my jointer table):


Some moderate taps with a hammer as you rotate the handle around will evenly compress the grain on the end of the handle:


Do some compressing, check the fit, and if needed do some more compressing until the ring will slide more than half-way on to the handle.

Striking rings are made in a variety of sizes, just like wedding rings, and sometime things get mixed up at the shipping end and you get a ring which is too large for the handle or too small. Too large a ring and it slides on too far, and too small and it can barely be started. If you find yourself with the over-sized ring, there is no recourse for fitting - you must obtain a more suitably sized ring. If the ring is a bit tight, you may have to carefully pare away a little material for the handle end, and do some grain compression - termed ki-goroshi, or 'wood killing' - until you obtain the right fit. You want to avoid hacking too much wood off the handle, and you want to avoid mashing the end by overdoing the compression hits.

Some handles are a bit more barrel-shaped than others and the striking ring fit ramps up quickly to tightness. Other handles are more nearly cylindrical, and it is easy to drive the ring on further than might be ideal, as happened with the Kunitoshi:


In the above picture you see about 3~4mm of handle protrusion, which, though some people out there say is an acceptable amount, is really too much. If you try to mushroom over the projecting wood, you will make a mess of the end, or render the striking ring less useful than it might be. The solution is to slice a bit of handle off with a saw:
 

A few moments later, the handle has the more ideal 1mm of protrusion:


At this point, many Japanese carpenters simply start bashing away on the end of the handle to mushroom the wood over, and the result is often functional enough but a bit less than attractive. In some places you will read that the end of the handle should be dipped in water to soften the grain, and then the hammer work can begin. I have even see on a few websites and forums full photo-essays where people actually soak the end of the chisel a few centimeters deep in water and leave it overnight to swell the wood. This is a terrible idea and cannot be recommended at all. Why? Doesn't the water swell the wood nicely? Well, sure, soaking the end of the tool in water will swell the handle end quite nicely. The problem is what happens down the line.  The handle won't stay swollen, unless regular dunks in water are planned, which is an odd way to maintain a tool.

The only water that should be allowed near a Japanese chisel or plane is that used when sharpening, and that is all carefully wiped off afterwards and some camellia oil wiped on the tool.

Soaking the end of a chisel in water does two deleterious things:

1) the handle end wood swells and compresses even further against the striking ring. Later, as the handle loses moisture and re-acclimatizes to ambient humidity, the over-compressed wood will shrink away from the ring and the ring will be loose. Soon enough the end of the handle starts to degrade.

2) a damp handle and an iron ring combine to produce a film of rust on the inside of the ring. sometimes this film of rust helps keep thing together for a while, but in the end, damages the ring.

If you're a believer in soaking tools in water, then it would seem to follow that when one's plane blade gets loose in the dai at certain times of the year the answer is to soak the plane in a bucket of water to tighten the fit. Madness!

I used to rub a drop or two of water on the end of the handle and use a household steam iron to heat and soften the end grain before hammering on it, however I have found a much better approach, using no water at all, one learned by reading about how old wooden wheels were properly tightened when they got loose. The secret weapons are turpentine and linseed oil:


As you can see, the function of the turpentine is to help the oil penetrate the handle wood:


The mix soaks into the handle, the wood is swelled slightly, and the oil eventually hardens and reduces the amount of moisture exchange in the handle end, thus preserving the fit over the year.

I mix the two parts together in a jar, 1 part oil to 10 parts turpentine, and then dunk the handles in:


Again, if you are sensitive to chemical and solvents, be sure to work in a well-ventilated area and use a respirator.

Different woods absorb at different rates. Like western Red Oak, Japanese red oak more readily wicks the oil/turp. mix up. After 4 hours or so, the red oak handle is removed:


Now for the hammer work - I prefer a funate-genno, or boat builder's hammer, because of its pointed end. The end is pointed, but not sharp-cornered at the points.

I place the chisel tip back on the block of wood, and start a series of short taps on the end of the handle, working from the center outward in a spiraling fashion:


If you lack a hammer like this one, a regular hammer can be used - simply carefully strike the wood using the corner of the head. Again, it is better that the corner of the head not be sharp.

The idea is to compress and move the wood down and outward, little by little, to mushroom the wood slightly over the ring. I occasionally switch to using the head of the hammer, dealing the end dozens of glancing blows to smooth the surface while compressing it:


Some people hit the chisel while holding it in the air with one hand, but I much prefer to set it onto the wood block, as I think it is faster and simpler to do so.

You want to make lots and lots of percussive strikes - you're not trying to maul it. In time, a clean shallow dome on the top of the chisel will be produced and the mushroomed wood will partially cover the top edge of the ring.

Getting closer in this shot:


 A view of the completed chisel end:


The white oak handle on the Yamahiro took a while longer soaking, but the process with the hammer work was the same. The result:


The Yamahiro has the more expensive type of handles made from a branch with the pith in the middle.

Then I give the rest of the handle a light wipe of oil and set it aside. Some oil may continue to weep out of the handle in the next day or two, but can be easily wiped up as it occurs.

That does it for setting the rings. Next time I'll sharpen up and see how they cut. I hope you'll stay tuned, and thanks for coming by.

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