Sunday, April 29, 2012

The Story of the Gazebo (VII)

I've let a few weeks slip by in this post series and some of you may have forgotten about it. I began by considering gazebo structural designs and patterns, both east and west and in the last post began sharing some drawings of a pentagonal gazebo with reciprocal roof structure which I have designed. I'd like to continue on then with a few more pictures of my design.

These posts are of my own design concept (and are copyrighted), and are intended to show the general arrangement of pieces in the structure. So, certain joinery and geometrical details have been omitted from the illustrations. I take the liberty of noting that if you seek to emulate this design in some manner, be forewarned that it is somewhat difficult to execute. Pentagonal roof framing with a reciprocal support ring composed of parallelogram shaped beams, and incorporating a double roof with curved eaves is not a basic roof form. Ideally, you will have want to have mastered regular hip roof framing with joined timbers, then polygonal roof framing with timbers, and then standard hip roof, double form, with curved eave before venturing into this territory.

At the conclusion of the last post, the reciprocal beam assembly was in place and the lower hip rafter were fitted:


You can see how the reciprocal beams have been extended beyond the wall plate to pick up the outrigger beam at midpoint. Also, note that the upper ends of the reciprocal beams have been trimmed so as to form a leveled surface.

Next, an inner purlin ring is fitted:


Then the main lower hip rafters are fitted:


Next, the common rafters are shown, which, in this example are of parallel type not fanned:


Atop the common rafters are two layers of perimeter eave fascia, the hirokomai and yodo respectively:


A perspective view of the half-completed roof structure, which shows the curved eave line a bit better:


A view from directly above:


And the view which is a prime consideration in the design - inside the building looking up (click the image to enlarge):


A bit like a snowflake, no?

In the next post in the series I will add more parts as the roof structure builds. I hope you've enjoyed the tour so far. Thanks for dropping by the Carpentry Way.  On to part 8

Friday, April 27, 2012

Two on Test (Part 4)

In the previous post I spent some time fitting the hoops, kashira, to the chisel handles of these two Japanese bench chisels, o-ire-nomi. The next step is to prepare the cutting edge.

Japanese chisels, marking knives, and plane blades are put together with a traditional technique involving forge welding a hard cutting steel to a soft iron backing. The forge welding and subsequent cooling often can cause some amount of warping/cupping, and it is up to the skill of the smith's technical expertise to minimize the effect. Essentially, the cutting steel, as it cools and shrinks, tends to exert a disproportionate deforming effect on the soft iron backing, and it is not uncommon to find brand new chisels and planes in which the underside of the blade, or ura, is cupped hollow to some degree. Sometimes the ura has been flattened well after forging but if a few months have gone by residual stresses can continue to work themselves out and cause the tool to be a little less flat. Hence the reason the tool comes to you new in the box in a roughly sharpened state only.

One could place the ura of the tool on a surface plate and see what thickness of feeler gauge can be inserted here and there, however having numbers to work with is not necessarily all that useful. It is more to the point to determine what sort of shape the ura has before embarking upon a sharpening process. For instance, with many brand new plane blades, it is often the case they you need to tap out right away, before doing any sharpening at all. It depends upon the condition of the ura.

With chisels, since they do not fit into a wedged opening in a plane block, the procedure is a bit different. Rarely does one have to tap out a chisel, unless an obsession with a beautiful ura has taken over one's mind. Watch out for that.

The first thing I do is flatten a finishing stone and then rub the chisel, ura side down, on the stone a few times to see what sort of marks are left on the stone. Those marks tell me about the condition of the ura.

Starting with the Yamahiro then:


The Yamahiro leaves two streaks on the stone, one at the cutting edge area, and one at the far end of the hollow along the edge of the stone.  A chisel with this shape of hollow will be somewhat prone to digging in when paring and if you were to simply work on flattening the entire back you would produce an ura with an unattractive appearance, one in which the landing at the blade edge is wide, and in which the landing at the far end of the hollow is also thick/wide. It will also be impossible to produce an even finish on the hollow as one slides the back on and off the stone in flattening. This shape of hollow means I need to give some extra effort in flattening the steel near the cutting edge and avoid placing the entire hollow on the stone for the time being.

Let's see how the Kunitoshi does:


Here we have the exact opposite situation to the Yamahiro - the mid section of the hollow is riding on the stone, and the cutting edge and rear end of the hollow are riding clear. A blade left in this condition would not pare well when slid along its ura, and the temptation would be there to angle the chisel up at the handle end to get the blade to engage, which it would, but not always especially predictably.

Of the two chisels, I find the condition of the Kunitoshi to be somewhat easier to deal with. I only need to keep attention on the cutting edge area while sharpening and feather in the ura length up and back until I have put about half the chisel on the stone, more or less. There will be some tendency to make the sides of the hollow, the legs (ashi) as they are termed, a bit fat as the flattening proceeds, however I will do what I can to minimize that effect while creating a ura that is flat from the cutting edge back about 2/3rds of the way along. The landing on the Kunitoshi at the cutting edge is generous so there isn't much to be gained by tapping out. That process of flattening will make for a decently functional chisel, and as with any striking chisel I don't tend to fuss the back as much with setting the chisel up for paring work. It is a chopping tool mostly. For paring, you want the back as flat as you can get it for as long a distance as is practical, without making a mess of the ura. I have a separate set of paring chisels dedicated especially to that use.

So, first I work the two chisels on the coarse stone, which is a 1000 grit ceramic:


I do use two hands and unfortunately lack a third hand for taking photos, hence the one-handed staged photo.

The Yamahiro bevel was a little out of whack, leaving the edge non-90˚ in  relation to the side, so I concentrate my efforts on the high side to bring it down. Here's the appearance after the initial round of work:


The coarse stone does the most to affect the shape of the tool so it is important to keep it flat and to use the stone to get the tool the shape you want it to be. I re-flatten my stone several times in the course of working the bevel.

A little further along and you can see that the bevel is 98% flat now, with a slight untouched spot left in the lower left corner of the softer iron portion:


Once the bevel was completely flat, I re-flatten the stone and work the ura, which removed the wire-edge from the tool.

The Kunitoshi next. It didn't require much adjustment for shape and was done relatively quickly:


Then on to the next stone. I proceed on a pattern of grit doubling, more or less, so my next stone is 2000-grit, also ceramic (Kita-Yama brand).

The Yamahiro is starting to get flatter and cleaner:


The Kunitoshi after a round on the 2000:


Again, after the bevels, I work the ura on the same stone. When I'm done, I re-flatten the stone and put it away on the drying rack.

The next round is on the 5000 grit ceramic. Here's the ura on the Yamahiro after that go-round:


The bevel after the 5000:


And the Kunitoshi after the 5000 grit round, ura side:


Bevel:


Normally, I would stop at 5000 grit for a striking chisel, however this is the initial set up of the tool so I like to take the back out to the next level, which is 10,000 grit.

The Yamahiro ura after 10,000:


A check to see if the chisel will shave some hair off the back of my hand:


And same with the Kunitoshi:


Both chisels are white steel so my expectation is that they both would take a really keen edge. It will be up to the smith's skill though to see how durable those edges are. So far, I found the sharpening on the ceramics to be pleasant, especially on the 5000, which is a Shapton Pro stone. The Japanese would say that the grinding 'taste' was good (Try this bit of Japanese on your friends: togi aji ga ii desu ne). The 1000 I have (New Kent brand) was the least tasty of the lot, but it still cut adequately. Probably there is a more suitable 1000 grit stone for white steel. I'll do some digging around and see what I can find. Where's a knowledgeable sharpening stone guy when you need one?

Right, well that pretty much does it for setting up Japanese bench chisels. Over the next month I'll put these chisels to good use in a variety of woods and then come back with a 5th post in this thread and give my general impressions of the two brands. Thanks for tuning in and hope to see you next time. Comments always welcome.

Monday, April 23, 2012

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.

Friday, April 20, 2012

Two on Test (Part 2)

In the first post I introduced a couple of bench chisels, or o-ire nomi, that I have been supplied by Iida Hardware in Ōsaka. The chisels have been supplied at no charge, in exchange for my review, and I have no commercial association to the store, though I have done a fair bit of business with Tomohito, the owner, over the years and have found him excellent to deal with. I do look forward to forging a closer relationship with suppliers I can trust and recommend to others.

New Japanese chisels out of the box can be used right away, in the same way a car that has been partially reassembled can be taken out on the highway for a quick high speed run. Not recommended. Japanese edge tools don't come ready to go unless they are at the really cheap end of the spectrum. They arrive more like a kit that needs some work before the tool can be used fully - and this is a kit supplied without instructions, which does frustrate some folks to no end. All you need are some pieces of balsa and styrene cement and the party is on! Oh wait, what am I saying?!

Chisels are flattened and sharpened at the manufacturing end (sometimes by someone other than the chisel manufacturer), then combined with a handle, or tsuka, which might be of several varieties of wood but is most typically red or white Japanese oak. Added to the ends of the handle is a lower ferrule, or kuchi-gane (口金) and an upper striking ring or kashira ()  - sometimes, though less commonly, also called a sagari-wa, meaning 'drop-down ring' (下がり輪). Usually the same maker produces all the metal parts, though on cheaper tools the upper and lower rings may be supplied by an outside manufacturer. The handle is almost invariably supplied by an outside manufacturer,sometime the same people who make plane dai.

The first task with a new Japanese chisel is to remove the kashira. That's right - no assembly required, only dis-assembly. The crown ring usually isn't fastened on terribly tightly, so it is fairly easy to tap off. Some people slide a flat-sided hammer along the handle and tap the ring off that way, however I prefer to wrap a spot of painter's tape around the upper part of the handle, place it in the open end of a suitably sized spanner clamped to a table, and use a drift to tap the handle down:

The tape is a precaution against marring the handle. Note that in the photo I have had to keep at least one hand on the camera - you would, however, want that hand to actually be holding the chisel so that when you tap the dear tool doesn't take a trip to the floor. A few gentle taps and you should have the ring off.

Next, inspect the ring to see how it looks on the inside. A decent quality ring will have a smooth inner surface. A mass-produced cheaper tool will sometimes - usually, I mean - have rough spots and metal shards on the inside of the ring. If the inside has any roughness, it needs to be dealt with otherwise fitting the ring properly could be problematic. A larger size chainsaw file is a very good tool for that tuning work. In this case, both rings were quite good inside and will need very little attention:


The rings are tapered internally at one end, the same end which fits first onto the handle. You want to be sure which way around the ring goes before fitting it to the handle.

With the ring off, I peel the manufacturer's sticker off the tsuka:


Here we have our two chisels, free of kashira and labels:


Nomi are shipped with a coating of lacquer on them, which protects against rust and damage from transport. You can leave it on there, but the partially worn lacquer looks a bit shabby after a while and the feel of the tool in one's hand is not quite as nice. It's a simple matter to remove the lacquer provided you have the right solvent. It's called 'lacquer thinner' and you will find it at your local hardware store:


What I do is place a clean cloth in a plastic tub and saturate the cloth with thinner. Using a wire helps direct the thinner from the spout into the container and not all over everything else:


Be sure to be using the thinner in well-ventilated conditions, and please, no smoking. If you're more sensitive to chemicals in general, you may wish to wear a respirator.

I then wrap the chisels in the thinner-soaked cotton and let them sit for 5~10 minutes. Then pull the chisels out, wipe/scrub them a few times with the soaked cloth, then wipe off the tool with a clean cloth. When done, the handle and shank, etc., will be squeaky clean, literally:


With the lacquer removed, we can get a better look at the forge weld on these two chisels. The Yamahiro first:


Notice that the line between hard steel (the shiny bit) and soft iron is quite even, and that the hard steel wraps around each side of the blade fairly evenly?  Those are good signs of skill in forge work.

The Kunitoshi brand tool has a slightly less cleanly done forge weld, however it is free of voids and decent:


The back of the Kunitoshi had a curious glob of metal stuck in place:


 I wasn't quite sure what it was, however it must be some sort of artifact from the grinding process on the back. I carefully gave it some lovin' with a needle file:


All better:


Next time,I'll sharpen the tools and fit the kashira back on. Stay tuned and thanks for visiting.