Thursday, August 30, 2012

A New V-12

A bit of a tangent from woodworking-related topics today. This video of a Spanish machinist constructing a fully-working miniature 12-cylinder engine brought a smile to my face, partly out of an appreciation for skilled craftsmanship of any kind, partly due to a personal liking for precision and metal craft -and damn! - it's pretty exciting to watch! With all the parts, reminds me of some furniture projects too. It's in Spanish, but that shouldn't get in the way of understanding what's going on.

Hope you like it:

Wednesday, August 29, 2012

Leaving Port

The aircraft carrier, my 16" Oliver 166 jointer, has taken a 90˚ swing in position and is preparing to leave dock:


I removed the fence so as to lighten the load by 100lbs. or so.


That is one hefty lump of cast iron and it took several hours work to build up a sturdy pallet and wrangle the beast into place. It's now bolted down so shouldn't be going anywhere without permission.  It will be taking a journey into southern lands, known as 'Connecticut', where it has found an appreciative new owner. I'm thinking a multi-gun salute would be appropriate for its grand farewell. It has served me well.

I am out with my fishing rod trying to see what new beast I can land. I'm thinking something longer and wider. Stay tuned.

Monday, August 27, 2012

2012 Northeast Tour

I just came back from a week's vacation, where my wife and I did a driving tour of a section of the the Northeast, as follows:


As you can see, we circled up from Massachusetts, into Vermont, then north to Montreal, Quebec, over to Quebec City, and then up the the Saguenay region of Quebec, where we did some camping. Then we drove down through New Brunswick, a Canadian Province I had never visited before, and stopped a night in its capital city of Saint John. Our trip finished with a trek through Maine, coming through the 'down east' region over to Bangor, where we stayed a night, and concluded with a wind down the coast route 1A, a brief transit through New Hampshire, and back to our home in W. Massachusetts. I took some wood- and architecture-related photos along the way which I thought might be of interest to readers here.

Our stop in Montreal allowed me to visit the Canadian Centre for Architecture, which has a library containing probably the most extensive collection of French traditional carpentry texts in N. America. As I was a researcher from out of Province, they opened up the library outside of normal visiting hours and let me in for a look-see. I was finally able to view an 11-volume set on carpentry put out by the Compannage Librarie in Paris back in the 1980's. I was eager to finally get to see it, however it was not quite what I had expected. Instead of bound volumes as normal sort of books, each box contains a volume, comprised of 8~12 folios wrapped in paper, all the pages loose-leaf so to speak. I didn't really think it was such a great format. The section of descriptive geometry for carpentry was much smaller than I had hoped, which was a disappointment. I spent a good two hours thumbing through all the volumes and in the end concluded that it was good I hadn't ventured the €1400 it would cost to buy used.

The Library also had an original edition of the Mazerolle classic, and I discovered that the original was not a bound volume but comprised of large folded plates only. The newer edition you can buy is a perfect reproduction, so I suspect the original printing plates must have been obtained somehow. They also had the original 3-volume set from Delataille, Art Du Trait Pratique De Charpente, and unlike the copy-of-a-copy-of-a-copy that I have, the original was fairly clear and legible. Still incredibly cryptic, but legible, which was a big improvement.

Then I came across an intriguing volume by a mathematician names Joseph Alphonse Adhémar, (1797-1862), entitled Cours de Mathematiques à l'usage de l'ingenieur Civil. This work was published in 14 editions, from 1832 until 1856. I looked at their 1854 edition, which was in superb condition. Here's the title page:



Adhémar was a French mathematician who came into prominence after publishing a book in 1842 on the potential connection between ice ages and astrophysical phenomena, Révolutions de la mer. He then wrote Cours de Mathematiques in 1846, followed by a few additional works on descriptive geometry, linear perspective, and the related topic of shadows. While a book by a mathematician on civil engineering might seem somewhat unrelated to carpentry, in fact a huge amount of civil engineering in that day and age concerned timber structures and their connections. The book is filled with some incredible stuff, like these intricate compound internally tabled beams:


The illustrations were really  something - take a look at these sketches of truss framing:


Some illustrations of curved log layout:



I was really blown away by that book. I'm going to have to try and get a decent copy sometime. It won't be cheap.

As I had photographed a fair amount of Quebec's house architecture on my visit there last year, I didn't seek out too much more in that vein. I did however spot a house in Île d'Orléans, an island in the Saint Lawrence River just near Quebec city, that had recently been re-roofed with the lovely asymmetrical galvanized shingles seen on so many houses in the area:


By the way, click on any of the above pictures for a larger picture.

Down in New Brunswick we found the architecture - and food - to be far less interesting than in Quebec, however upon making a stop in a town called Hartland, we came across this wonder:


The is the longest covered bridge in the world, at nearly 1300' (396m):


I've even got the t-shirt now.

Like a lot of covered bridges, there is a lot of metal present, especially for those members which function in tension. Engineers however, like to spec. steel replacement pieces wherever they can, even if timber may have functioned adequately, like for bracing. On the other hand, knee braces are poor resisters of tension, and reinforcement or replacement of these members with steel makes a lot of good sense, as with these large braces found at the entrance and exit of the bridge:


 A look at the undercarriage:


 While most covered bridges in Vermont and New Hampshire seem to be of the Town Lattice type, all of the bridges I came across in Quebec and New Brunswick were of the otherwise-rare Howe Trussed type:


One point of interest for my wife and I in New Brunswick was to check out the Bay of Fundy, site of some of the highest tides in the world. We had a delightful drive out to the Bay of Fundy National Park, and on the way came across some more covered bridges, like this one:



Again, the Howe truss seems to be de rigueur in New Brunswick:


Note the metal rod to reinforce the knee brace at the entry truss, and the octagonal straining beam to which it attaches:


There was a second bridge a stone's throw from the first, which had slightly different detailing with the straining beam:


Some recent timber restoration work was evident, along with some metal knee braces in lieu of wood:


The undercarriage - note the metal tension rods underneath the primary truss chords:


One of the bolted hammerhead splices seen in the primary spanning truss chords:


As our trip wound down, we arrived in Bangor Maine. I had heard - as had quite a few others, apparently - that Steven King had a residence in Bangor, which was famous for its 'wrought iron fence'. Intrigued, and thinking that Steven King might be one of the few people out there who could actually afford a genuine wrought iron fence, I took a trip to see his place on W. Broadway, in an area of posh homes. To no great surprise, the fence was simply a mild steel affair, no wrought iron to be seen:


'Wrought  iron' is frequently described, but, alas, not too often seen. I think that few people really have any idea what it actually is. That said, the fabrication work with the mild steel was quite creative and well-executed:




Not the sort of fence most people would want, but fun to look at. Knowing the owner by his books, the fence is a good fit of course. King's property appeared to comprise two houses, and the right hand side of the two, which virtually all of the photographers seem to ignore, had the more interesting detailing in my view:


A lot of houses in this part of Bangor are in the Second Empire Style, and Mansards - which should really be called 'Mansart' roofs - were very much in evidence:


I see the multi-volume set by the compagnons society uses the term 'Mansart' now, though older French books were using 'Mansard'. It may well be impossible to change this word use now it is so well established, but I will try anyhow.

Another one:


I thought the dormer on this garage was unusual in form:


This delightful house has two towers, one octagonal and the other circular, with an unusual copper finial atop each roof:


In another part of town I spotted this somewhat ungainly structure with incorporated octagonal roof - kind of a neat idea over a sleeping porch if you ask me (though I would detail it differently):


On the final day of our adventure I popped by the Center For Furniture Craftsmanship in Rockland, ME, where there is a gallery of current instructor's work. Great schol, but like a lot of modern furniture, plywood and veneers are strong elements in many of the pieces, so I was not especially interested in most of what I saw. I did like this chair on display in the gallery, which sat very well, if you know what I mean, and rocked pleasingly too:



The material is English Walnut:


I liked the lines of the curved parts and the sensuousness minimalism of the piece. Glued together with floating tenons, glue laminations - not my way of making, but the result is a beautiful piece. Well done by the maker.

Well, that about wraps up my account of 'How I spent my Summer Vacation'. I hope readers found the tour of as much interest as I did. Thanks for coming by the Carpentry Way and comments always welcome. googlefec1ae8fd0572e83.html

Wednesday, August 22, 2012

Takin' it to the Mat

Lately I've been designing some Japanese interior spaces complete with tatami and shōji. Tatami, in case you were unaware, are a type of floor mat used in Japanese traditional rooms, usually composed of rice straw with a covering of soft rush. Here's a picture of a couple of mat men making tatami in a 19th century colorized photo (from the Smithsonian Institution's Online Collection):


Tatami are typically rectangular, sized on a 1:2 aspect, that is, the length is two times the width, though other shapes and proportions are occasionally encountered. Tatami mats come in a few standard sizes, most typically 90cmx180cm, however many other sizes can be made.

          The word 'tatami' comes from the verb tatamu, written as: 畳む. The character '' is a simplification of an earlier character, , which breaks down into '' at top and '' on the bottom. While '' appears to be rice field, '', tripled, this is in fact misleading. The rice field kanji is doing a stand-in for something else. An early seal character for '' shows this:
Thus the element '' on top of the character is not in fact rice field tripled but is the element '' tripled. The character '' is in turn a simplified version of '', which is a pictograph of meat. Tripling the element suggests a pile of meat. Below that, we have '', which comprises '' roof/building on top and, originally, '' below. Another pile of meat since this is the element '' we just saw before, doubled. This lower element, , is therefore tall, neat pile of meat in a room.

The modern form '畳' means "to fold and pile" things in general, and has little to do with meat or buildings. Kanji etymology can get quite convoluted but I find them most intriguing to tease out.

       Since tatami mats are in a 1:2 aspect, they are readily tesselated, like dominoes. Certain room configurations, in order to be fully tiled, may require tatami with a 1:1 aspect - the half-mat.

Here are some tatami tiling patterns, starting with 3-mat rooms (upper left) to 4.5-mat rooms (upper right) then 6- and 8-mat rooms below that:



Like kanji though, things are not so simple as they first appear when it comes to arranging these 1x2 mats. Notice that there are no 4-mat rooms listed above for instance. While there are numerous possible arrangements of mats in a given space, certain arrangements are simply not done - or were not done in the past. Perhaps the grip of tradition is growing ever looser in modern Japan so these rules about tatami arrangements may not be so strictly observed these days.

You will note in the above drawings that certain drawings have slightly differing descriptions after them. Take the two examples above of 3-mat rooms:


Notice that the arrangement on the left has "祝儀敷き"  written after the '3畳' (3-mat), and on the right side "不祝儀敷き" is written after the 3-mat. Just one character separates them, and that might not be a big deal except for the fact that the character, , means un-, or not-.  On the left above we have a 3-mat arrangement considered auspicious, as  祝儀, read shūgi, means 'fortunate', 'celebratory', 'successful', etc. On the right is an arrangement considered unfortunate, or inauspicious, fushūgi.

What governs whether something is 'auspicious' or 'inauspicious' is pretty much a matter of superstition. I would suspect virtually all cultures have them in one form or another. And in all cultures, I suspect, there are individuals who are very concerned about superstitions and those who think they are irrelevant. Some, nevertheless will follow superstitions even while not really believing in them, 'just in case'. The 15th century text on Chinese carpentry, the Lu Ban Jing, for example, is largely concerned with superstition, both on the side of the carpenter's practice and upon the part of the client for that carpentry. 

In Japan, the number '4' can be read as shi. Shi, however, is also the reading for a character meaning death (). So, in counting, Japanese people tend to avoid saying shi and instead use the reading yon instead. This practice would be more strictly followed around a hospital. Surprisingly, this curious association of phonemes between '4' and 'death' is also present in Korean, most dialects of Chinese, Hakka, and Vietnamese - I say 'curious' because these languages are not as linguistically close as one might think. 

Similar to the west where tall buildings 'lack' a 13th floor (as far as the elevator buttons are concerned), Japanese avoidance of the number '4' extends to many areas - buildings, parking lots, designations on ships and cars, room numbering, etc.. This superstition of the number 4 even gets its own name, in the English language at least: tetraphobia

In Japan, a room to take 4 mats would be avoided generally, and having 4 mats meet at their corners, forming at their meeting a '+' shape is to be avoided in any mat arrangement. Perhaps the reason being that the '+' shape, when rotated, forms an 'X', which is the symbol for not-, don't-. The Japanese also have a superstition about treading on the edges of the mats themselves, which is thought to bring misfortune. In the traditional martial arts of Japan, practicioners were taught to avoid stepping on the cracks formed between the mats, possibly to avoid tripping, possibly to avoid being struck by a knife shoved up from the floor below by some enemy.

Curiously enough, superstitions about cracks, spread, if you'll pardon the word-play, far and wide. According to John A. Dowell in and article cited in Encyclopedia of Popular American Beliefs and Superstitions,
"In many European- and African-American folk belief systems, cracks in the earth, in walls or between walls and doors, or in sidewalks or floors frequently indicate fissures in metaphysical boundaries between this and some other - often nefarious - world. Employing sympathetic magic, people may interact with such boundaries. These clefts in the boundaries may be divided intro three general types: the most common, which deal with health and the family; those concerning either placating or taunting the supernatural spirit world; and those which manipulate the physical environment."
From this belief system comes down the children's rhyme, "Step on a crack, break your mother's back, step on a line break your father's spine." It's charming the little ditties that get passed on to the younger generation, huh?

In Japanese interior architecture, the fear of '4' and the fear of cracks means that many possible tatami mat arrangements are avoided. In some cases, too, the arrangement of mats in a room might be temporarily rearranged for inauspicious occasions, such as funerals. Consider the following two possible mat arrangements for a 4.5-mat room:
The arrangement on the left is fine, while the arrangement on the right is considered no good because of the four mat corners coming together in one spot.

Here are another couple of arrangements for a 4.5-mat room:
These mat patterns look extremely similar to one another, however the arrangement on the right is considered most unfortunate. Why? Well, it turns out that in previous eras when a person was to commit ritual suicide, seppuku, in a room of 4.5 mats, the mats were arranged as seen on the right side. The mats may have been arranged in that pattern for such an occasion due to similarity in form to a Buddhist symbol we would term in the west a 'left-facing swastika', '':
In this context, the symbolic alignment of mats into the '' form may be taken to mean 'the eternal afterlife'.  In Japanese, the symbol '卍' is taken to refer to Buddhism in general, and if you look on a Japanese map and see that symbol, it is to indicate the location of a Buddhist temple.

The Chinese brought in the symbol along with Buddhism from India, and from there is traveled to Japan. Swastika comes from the Sanskrit svastika, and is a good luck symbol. That the Nazi party in Germany adopted a right-facing swastika as their party symbol is unfortunate as it can result in some westerners misinterpreting the left-facing swastika from East Asia as having something to do with Nazism, which it does not.

The cracks between tatami are also crucial concerns when placing the mats in reference to entry doors and decorative alcoves, tokonoma. It is considered inauspicious to have either an entry/exit door or alcove aligned axially to a split between mats:


On the drawing at left, both the alcove (in black at upper right) and accompanying oshi-ire below it are adjacent to cracks in the mats. The drawing at right shows the proper way to configure the six mats.

It is also bad form to have a single entry/exit door open onto the narrow edge of one mat:


So, in designing a Japanese room, it is not a simple matter of working with a mat multiples as an organizing theme, as if were a simple dominoes problem. Configuring the room size on that factor and no other, if traditional Japanese mores and beliefs are to be taken into account, will inevitably lead to outcomes which a classically enculturated Japanese would see as inappropriate.

Thanks for coming by the Carpentry and I hope you enjoyed this look at tatami mats.

Thursday, August 16, 2012

Chip off the Old Block (VII)

Today marks the first guest post on the Carpentry Way. Mike Laine is a professional woodworker based in the San Francisco Bay area running a company walled Wooden Heart. Mike has put in many years of work for two California-based companies specializing in the design and fabrication of Japanese architecture, and I worked together with Mike on the Ellison project several years ago. Mike is a long-standing member of the Timber Framer's Guild and has participated in several Kezurō-kai gatherings, both in the US and in Japan. His passion for the Japanese hand plane and proficiency in Japanese woodworking is well established.

-    -    -    -    -    -    -    -   -

    Chipbreakers, the sub-blade, the orphan in the plane assembly, borders on an afterthought in the Japanese plane.  I don’t know exactly when the chipbreaker was added to the Japanese plane, but I’m told it was introduced by the first Westerners to visit Japan after the 200 years of isolation enforced by the Tokugawa shogunate.  I get the feeling that even today, it is grudgingly accepted as useful, and still considered superfluous.  Indeed, a plane can perform superbly without a chipbreaker, and some claim that the best surfaces are produced without a chipbreaker, but for everyday work, and for woods that aren’t plane perfect, they are essential.  Personally,  I love how they tame unruly woods, and add an element of reliability to finish planing, but I will leave the merits of the chipbreaker for another discussion.  My interest here is to discuss how a chipbreaker is best fitted into the plane.

    In a high quality Japanese plane, the chipbreaker is made with nearly the same level of finesse as the main blade.  They are bi-metal, beautifully made, and hand signed by the blade maker.  Occasionally, they are gracefully shaped so that the two upper corners rest on the main blade, but most often, the upper corners are dog eared, bent with a hammer, to make the contact points. Here's an example of a sub-blade with a more sophisticated shape, with the ears forged, not bent:


   
    The chipbreaker is held in place by wedging itself between the steel ‘chipbreaker bar’ (osae-bō) and the main blade.  When it is fitted properly, the sharpened edge of the chipbreaker creates a 'light-tight' fit at the cutting edge of the main blade.

      It is often difficult to achieve that good fit, due to a number of irregularities that commonly crop up in a Japanese plane.  For example, fitting the main blade into the body of the plane, the ‘dai,’ can introduce a distortion in the blade, such as a subtle twist.  If the top edge of the tapered dados that hold the blade are not perfectly parallel, this distortion happens. Also, the ‘chipbreaker bar’ is rarely installed parallel to the surface of the main blade. The upper face of the chipbreaker that contacts the osae-bō is randomly shaped, which means that the contact point with the osae-bō could be anywhere on the face of the cb.  If the cb face is concave, then the contact points with the c bar will be along the outside edges, if the face is convex, then the contact point might be closer to the center of the cb.  The evidence of this is that a cb that fits perfectly on a blade resting on your workbench may not fit at all when all parts are inserted into the plane.

    A solution to these problems is a simple design change to the cb.  First, change the two dog-eared contact points in the upper corners of the cb to a single contact point in the center...a tripod of sorts.  Second, dome the top edge of the cb so that even if the osae-bō is out of parallel, the pressure point on the cb will still be nearly centered.  The centerline pressure has several advantages.  If the polished surfaces of the blade and cb are flat - which is the carpenter’s job - the 'light-tight' fit is virtually guaranteed on the first try; there is no twist to fight because of uneven contact points.  The centerline pressure also influences the shape of the cutting edge of the main blade.  The center pressure helps create the ‘smile’ in the blade that keeps the corners from digging into the cut.  This problem is commonly addressed by sharpening a ‘smile’ in the main blade edge, but the cb can contribute to that when the pressure is correctly aligned.  In fact, if the ‘flat’ surface of the sharpened edge of the cb is just slightly eased at the edges, the ‘smile’ happens mechanically.
                               
    I had the tripod chip breakers made in Japan, with the help of Sayuri Suzuki.  She has been selling Japanese woodworking tools for many years, and still does.  I made a wood model of the chip breaker I wanted, and she sent it to a blacksmith in Japan, who made several sizes for me. Here's a couple:


Notice the scrape marks in the center of the cb on the left, evidence of the contact point with the chipbreaker bar.   The cb on the right was not made properly, and I had to grind a dome in the top face for a centerline pressure fit.  Both chipbreakers were easy to fit, and work perfectly.  If the Japanese blacksmiths were to take the tripod design seriously, and make them with the finesse  they are capable of, the tripod chipbreakers would be a nice addition to the plane kit.

Wednesday, August 15, 2012

Chip off the Old Block (VI)

Sixth post in a series looking at Japanese planes and their chipbreakers, osae-gane. Here's a refresher pic of the parts of the plane we have been looking at and their respective names:


Today we look at the fitting of the chipper to the rest of the plane, and this is a fit comprising three aspects:
  1. Fit of sub-blade to dai
  2. Fit of sub-blade to main blade
  3. Fit of sub-blade to osae-bō
Fitting the sub-blade to the dai is quite straightforward and should be checked with a new plane right away. Simply slide the sub-blade down into the opening of the block and assess the clearance to the sides of the throat - the sides are indicated in red on the following sketch:


Tightness in the fit between the edges of the chipper and the dai can happen at certain times of the year, especially with dai having flatsawn, or masame, grain orientation. This can also happen with dai made from woods which move a large amount due to humidity changes, exactly the sort of woods one does not want to employ for making plane dai.

If there is interference in the fit between sub-blade and dai mouth cheeks, the first place to look is at the edges of the sub-blade to see if there is any gross deformity or metal blobs attached, etc., that may be left over from the forging process. Generally you will find the chipper to be fine in this regard, so if the fit of the chipper to the block is tight, the remedy is to pare the insides of the mouth back a bit. To do this cleanly, one removes the osae-bō.

The fit of the chipbreaker to the main blade has been covered amply elsewhere I think, however I'll make a few observations all the same. Now, before one even looks at fitting the sub-blade to the main blade, the following steps must precede:
  1. The main blades ears, or mimi, are trimmed (i.e., ground back) so that the width of the blade edge is slightly narrower than the width of the mouth opening in the dai. If this step is left out, shavings at the corners of the blade will have no escapement and can jam up, affecting planing.
  2. The main blade has its back side, or ura, properly flattened and taken to a finish polish. Often, with new planes, tap-out precedes the flattening work. Anytime one needs to tap out the main blade later on in the plane's working life, the fit of the sub-blade to main blade needs to be revisited.
  3. The main blade is sharpened on its bevel side.
  4. The main blade is fitted to the dai.
  5. The width of the osae-gane is checked against the width of the main blade - ideally they are the same. If the sub-blade's corners project out to the sides from the main blade then they can be ground back to match.
  6. The ura of the osae-gane is flattened. This is a bit tricky to do as the entire chipbreaker has a curved profile and establishing a flat with a clean polish requires a few tricks. Since the chipbreaker is rarely going to be re-sharpened or re-flattened after initial set up, and does not have to fit to a tapered trench in the dai, attending to its ura flattening is less critical than it is for the main blade. The objective for the sub-blade is to obtain a clean flat backside right across the width, at least 3~4 mm wide. I can see that ura flattening requires a separate post really to be covered, so maybe I'll look at doing that in the near future.
  7.  The bevel of the osae-gane is flattened and polished, and then a secondary bevel is put on, as detailed in an early post in this thread.
Once both main blade and sub-blade are set up, they can be fitted to one another. One lays the main blade down, ura side uppermost, and places the sub-blade on top of it in the alignment and position it would normally take for planing - i.e., in line with the main blade and edge pulled back 0.2mm or so. Then it is time to gently tap the corners:


Here we have a situation somewhat akin to getting a table or chair with four legs to sit flat upon the floor. The chipbreaker has four corners which need to rest evenly on the 'floor' provided by the main blade. You tap to see if any clickety-clack sound can be produced, what the Japanese call gata-gata. If two diagonally opposed corners are high, then one of the other corners will be elevated off of the main blade's surface. If there is some gata-gata going on, then one must improve the fit so there is no gata-gata - by adjusting the chipbreaker at one of its upper ears, or mimi.

One has two choices in how the fit is adjusted. Either the ear which is high is brought down to meet the kannami surface, or the opposing ear, which is low and holding the whole works up off the surface, is brought up to allow its laterally opposed ear to come down. Why would one choose one option over the other? Well, if you'll excuse the resort to cheap rhetorical questions like that, I can say that the effect of each action (adjusting an ear up or down) affects the overall tension of fit between the sub-blade and main blade when they are pressed down in the plane mouth by the pressing stick, osae-bō. So it is a good idea to get a sense of how the fit under the osae-bō looking before making a decision about whether to bend the chipbreaker ear up or down. So, slide the main blade into the dai and tap it into working position. Then slide the sub-blade in and see how tight a fit one has between the underside of the osae-bō and the upper surface of the sub-blade. If you want a slightly tighter or looser fit, then one can adjust the relevant ear on the sub-blade accordingly.

Adjusting the ear on the sub-blade can be done in several ways. With the less expensive types of sub-blade, which may have no cutting steel forge welded into place, the ears are simply folded over. Many expensive sub-blades also have folded ears. Adjustment is generally by placing the chipper on an anvil with the ear dangling and tap the ear with a hammer to bend it down:


With the higher quality chipbreakers, which have their ears formed by thickening the sub-blade out towards the corners, or similar (see the previous post in this thread for a look at some different treatments) hammering on the fattened bits is not quite so much fun. While you can achieve some bending by way of the hammer, you are obviously fighting a bit against the thickness of the metal - it's often better to make adjustments to these kinds of sub-blades by filing the high spot down. Of course, if you must move an ear down so as to increase the tension of fit under the pressing pin, then tapping with a hammer is the means to do that. Be careful not to mar the chipbreaker when using the hammer, and be sure that your anvil does not have sharp edges as these will definitely mar the chipper.

Proceed judiciously with the adjustment work, checking the fit of the sub-blade onto the main blade. Keep going until all the gata-gata is gone. Once you cannot discern any rocking (a light touch is best here), the fit of the sub-blade to main blade has effectively become a tripod, as  the edge of the chipper forms on continuous, evenly placed fit along the ura of the main blade. The fit can be further checked by holding the blade and sub-blade together in their operating position and holding the sandwich, as it were, up to a light source to see if any light can be seen through the fit at the sub-blade edge. Be sure not to squeeze the blades too firmly together when doing this as you will not obtain a clear idea at to the fit since your hand pressure is deforming that fit. You want the blades to fit seamlessly to one another in an unstressed union.

Finally there is the matter of fitting the sub-blade to the osae-bō, which can only take place as a final step after all the previous steps have been completed. Fit the main blade into the dai and tap it down to operating position. Slide the sub-blade down until it is fitting snugly - hand pressure alone is sufficient here - and take a look at how the sub-blade's upper surface meets the underside of the pin. If you have a plane which you have been using for a while and have never looked at the fit of the sub-blade to the pressing pin then the sub-blade's upper surface can often tell you the story right away in that you can see where the surface has been marked by rubbing against the pin - here are a few examples:




What you want is a mark in the middle portion of the sub-blade. Ideally the sub-blade is made with a slight convexity across its width so that when it meets the pressing stick the push in in the center and the force is thereby evenly distributed across the sub-blade.

Sometimes though the sub-blade may have been carelessly prepared or the osae-bō may have been fitted into the dai imperfectly. One case is where the sub-blade and osae-bō rub against one another at one edge of the sub-blade (picture from mandara-ya's site in Japan):


The first thing to do here is to measure and check the positioning of the osae-bō to see if it is misaligned. If it is misaligned, then the typical remedy is to remove it, plug one or both of the pin mortises in the sides of the dai, then re-drill. The result will look like this:



A much worse situation is obtained when the sub-blade has little to no convexity and you obtain a fit where the osae-bō makes contact with the upper surface of the chipper at both edges:


This is an unfortunate situation, but not the end of the world. I think if the plane was brand new I'd send back the chipper and ask for one with a proper shape. This might not be the most convenient or rapidly-accomplished option however. Some people hammer on the middle of the osae-bō to bend it, so that it will press down in the middle of the sub-blade, however this is inadvisable I think. The problem with bending the osae-bō is that the bowed shape which results creates torsional leverage, which means that the insertion of the sub-blade and pressure against the underside of the bowed osae-bō will tend to want to rotate the pin itself down and around, thus reducing all that was apparently gained.

Actually there are only two solutions to this fitting problem if a new chipbreaker cannot be obtained. Either the upper surface of the sub-blade is ground down at the edges to achieve the desired single central contact point is achieved (which makes a mess of the chipbreaker at least in aesthetic terms), or the pin must be modified. The following pics are taken from mandara-ya - first up the pressing pin is removed and the marks from the upper surface of the sub-blade are observed:


The pin is then placed in a vise and the marked areas filed down:


The result:


The pin would then be refitted, carefully aligning the filed flats with the upper surface of the chipbreaker. When done, the pressing pin should be tight against the middle of the sub-blade, with space at the edges clearly visible.

That about covers the fitting of the conventional sub-blade to the rest of the plane. While the constituent parts of a Japanese kanna are rather unimposing, there are many details to achieving a good cohesive assembly that will enable superlative results to be obtained. In the next post in this series we'll have a perspective from a California-based craftsman who took a look at the chipbreaker and thought there might be another way to design it so as to make the fitting process more straightforward. I hope you'll stay tuned.

Thanks for visiting the Carpentry Way, your comments are always welcome. --- on to post 7