Let's try this link instead:

Japanese draw-bored mortise and tenon detail

I have a Makita portable hollow chisel mortising machine. I brought it back from Japan with me. I could probably order another one if you twist my arm and bribe me, however you may do just as well with a General International or Powermatic hollow chisel mortiser. Usually the peg mortise is reasonably close to an arris, so any hollow chisel mortising machine that can extend out over 6" across a timber will work for most connections. I got one at the College of the Rockies and we used it for the TF course when I was working there. Just needs a couple of outfeed supports - it worked well. The Makita beam mortiser is more ideally for softwoods - trying to poke large holes through on oak is probably not going to be a good time in anything larger than 5/8". Japanese pegs, or komi sen, usually aren't much bigger then 15mm though.

Hi Chris;

Neither link is working.

Thanks;
Jim

Hello,

Yes, we haven't seen such a sweeping statement in a while have we. Probably not so helpful except that it draws you out Chris, so that's good. I say that Japanese pegs are not draw bored mainly because it's true. But of course to say that Japanese peg holes are not drawn actually means that no Japanese joint has ever been draw bored by anyone and that cannot be right. Maybe better to qualify by saying it's not the equivalent joint to the one used in Western work. Look the technique was not feasible until there were augers or some kind of boring tool which in Japan is a gimlet - no timber framing tool, that. Sure its possible to chisel the entire square hole which was the way in Japan it was initially done and why the keyed joint dominates. Also the principle is fine if your after maximal stiffening throughout but Japanese construction is in principle about the right amount of flexibility, I mean a flexible joint and one highly tensioned don't go well together. So that's where I see incongruity. One other incongruity of the situation at hand I see is just what you bring up yourself, the relatively small cross section when you think that 15 mm is about the size of my pinky out at the tip. I do recall draw-boring being included in one book of Japanese joinery that also was quite keen on metal fasteners. The link you set up there probably contradicts what I write here but it doesn't seem to be connected right.

Greetings,

Don Wagstaff

Sorry about the link not working. not sure what to do about that, except provide the actual address where the pic is stored:

https://picasaweb.google.com/104943063435486564254/December62012#5818993359399316450

I have long found this forum very awkward to use for attaching pictures.

As to your comments Don, well, I see things a bit differently. Yes, you've drawn me out of my cave.

Pegs are not stiff connections, first of all. The draw bore is helpful in keeping the connection firmly together, in the case of a post and a beam say, during shrinkage and/or seasonal movement. I don't think it's purpose is primarily to stiffen the connection, since pegs are inherently flexible. That said, draw-boring does place a joint in tension, however that tension is going to vary - the peg needs to behave elastically to a certain extent. If the beam shrinks, the tension on the peg is going to ease.

Peg size and number, along with structural arrangement, timber size and joint detailing are significant factors that affect how much tension might be in a joint, however no pegged connection can resist much tension anyhow. The pegs will flex, and at a certain point relais will give or the peg will break.

'Draw-boring', to my way of thinking, is more about the principle of off-setting the peg hole in mortise and tenon so that the peg has to elastically bend around as it is driven through. I don't take the word 'boring' to only mean with a drill or auger. 'Bore' simply means to make a hole. Whether the peg mortise is round or square doesn't affect that off-setting mechanism, so making an argument that the technique was not 'feasible' in Japan until augers came along is not convincing in my view. Also, to say the joint used in Japan is 'not equivalent' to the one used in western work is misleading - they are alike in principle and only differ in respect to the shape of the mortise for the peg. I would say they are equivalent.

The argument about "Japanese construction is in principle about the right amount of flexibility, I mean a flexible joint and one highly tensioned don't go well together" is not winning me over. I think too much is made of that 'flexibility' by some writers, and it is a bit simplistic to characterize an entire framing system, especially one with great diversity in methods, in that manner. Diagonal bracing has been employed in wall systems in Japan for 150 years, as one counter-point. Connections which suffer tension in Japanese framing, like western framing, are typically reinforced with metal. Case in point would be angled wall bracing, which the Japanese do not peg but tie in place with metal and hide in the wall. Pegging diagonal braces is problematic, as you probably know.

I might add that diagonally braced systems also suffer from flexure, both by lateral deformation of the timbers by the braces, and insufficient stiffness at the pegged connections.

Many scarf connections, like kanawa-tsugi, or sao-tsugi (rod mortise and tenon) joints, involve driving in a wedge or pin to drive the end grain bearing surfaces of each joint half in opposite directions, placing the joint in a degree of tension. How does this square with your assertion that tension in the connections is somehow incompatible with Japanese framing practices?

It would be correct to say, I think, that Japanese framing is primarily a system of framing components to bear compression loads rather than tension. That's a logical way to employ solid wood in a structure, is it not?

I also might point out that after your argument that creating tension in a joint is somehow alien to Japanese carpentry practice, you then state that a 15mm peg having a relatively small cross section - aren't you therefore saying that such a connection would be less capable of creating tension? It seems like a contradiction.

I can add that 15 mm pegs are fairly standard in Japanese framing because the structural parts to which they associate have been fairly standardized in most respects for the past 100 years or so - 105mm or 120mm post sections, for instance. In much the same way, western framing might most often be done with 8"x8" posts and 3/4" pegs. It doesn't mean that custom sizes and larger/smaller pegs are not employed in other situations.

I think the offset, draw-bored connection has some advantages when done with a square peg mortise rather than a round one. And it is still done, often enough, simply by chiseling work.

I can add to the foregoing that...

Thinking about the scarf joint kanawa-tsugi a little further, I realize that it is a little hard to say whether the net effect of driving in the wedging pin is to put the joint in compression or tension. Obviously the end grain abutments are in compression. So that might not be such a good example to have brought forth.

I think the case is much clearer with the rod joint that the internal tension of the joint is increased as the wedges and/or peg are driven in. Also true for adapted forms of the joint, as seen in 2-, 3- and 4-way splined connections.

Interjection. My first primary goal when draw boring the peg holes is not to load the joint but to choose that when I insert the peg it does not push the joint apart. The risk of marking exactly where the theological peg will fall can vary and the end result can be the joint being pushed apart. Even pulling the members together with ratchets and straps and then boring risks, in time, the joint being held apart. I find the result of drawing boring and having the joint be pulled together during and after the frame a perk, most joinery is in compression anyway. I would find it odd the the eastern influences would not draw the joinery.

Hello,

The purpose aside, the beauty of the technique, (so called draw boring) is when all goes as intended and the peg or pegs are driven home, the joint is incredibly effective. It does amaze me how much impact on the overall integrity of, it's a mortice and tenon were on about here right, the joint this aspect has. What does that mean? It makes the joint solid and stiff. So, no, it's not just about the aesthetics of closing up the connection it's equally about how well an individual joint performs its function within the whole of the construction, and rigidity is clearly the trajectory, conceptually and practically of European style construction, not absolute rigidity at all but rigidity in the Cartesian sense of the human effort to resist the condition of the natural world. The worth of pegging in this way depends on reaching an optimal balance of forces.

If we are going to look at Japanese construction and European, which has been done before by people like Grubner and Zwerger for example then I think it's valid to bring up flexibility in Japanese construction. I do buy into the point that the joinery and related techniques reflect among other things naturally but in large part even, the sheer demands of the natural environment prone to earthquakes.

So the question is then where does this pegged joint fit into the Japanese context? I am saying it is marginal at best and even go so far as to say, without drawing any further conclusions but just as a fact, that it was introduced relatively late, 150 years ago sounds about right, from the west, where, in European joinery it's equivalent place is central, it's integral to particular joints and to the entire construction.

Chris, Do you actually think the way the hole is made is so insignificant to it's widespread use, or in the way I put it before its feasibility? I can't believe it. Don't get all to caught up in the name, here they say toogen which can mean to draw as in a horse drawn wagon.

Well my response admittedly is general - for the time being - but I've got the side of the barn torn out and need to get a new post in there so got to go for now.

Greetings,

Don Wagstaff

Don,

if Graubner and Zwerger are your primary sources of information on Japanese carpentry, then I can understand why you might be a little askew in your perceptions of Japanese carpentry. Graubner's 'Encyclopedia of Wood Joints' is filled with errors and should not be relied upon as anything other than a general survey.

Anyway, not much interested in engaging further - your argument a few posts back was that draw boring is not done in Japanese traditional construction, and I've shown an example of that very thing and described why I think it is used. I'm sure there are carpenters there who do not employ that technique, just as there are timber framers in other places who do not.

~C

Hello,

The two authors I mention only because they write explicitly to compare Japanese and Western Carpentry. This is at the core of the topic which was not technical but implied a incorporation of Japanese style into Western Framing. And what I was trying to get at is the question of where the off-set boring and pegging fits into Japanese joinery regardless of how much it is or is not employed, with the intention that a general understanding can help clarify the specific use. I use the technique most commonly employed in boring the hole as an explanation of why draw boring is foreign to Japanese joinery where the wedged or keyed joint is used in its place.

Greetings,

Don Wagstaff

Hello All,

I know I'm coming to this conversation late, but for the sake of the public record, and Chris's support. There has been some information on this post thread I must comment on. I have PM'd the original poster and offered my assistance with the his challenge of square pegs.

For what ever reason, when Americans or Europeans typically speak of timber framing in Asia, they seem to go in their minds, to Japan first. I have always found this a bit strange. Timber framing, was a craft of the ship wright as well as the house wright, and originated in the Middle East, moving into Asian thousands of years ahead of Europe. If you consider what the North American Pacific Coast People build as timber framing, as I do, then they are even ahead of Europe. The Shang Dynasty of China had an architectural timber frame wood culture in complexities that rivals today, and that was in the 12 century BCE; at which time most of Europe was just coming our of their Neolithic period with only basic, at best, post and fork lashed frames. When I read comments like the following, I become incensed:

"speaking of draw bore pegged joints,"


From the West? You mean Europe? This statement, beside being completely and utterly untrue, further demonstrates a continued European/American since of superiority; whether intentional or otherwise, it presents that way.

"Draw Boring," was practice in Asia for thousands of years ahead of European architecture, and in my specialty, folk architecture, the trunnels may be as large as 30 mm. I know in Japanese Minka, they are commonly over 20 mm or larger and can be found in frames that are over 300 plus years old. So, know they did not come from Europe.

As far as the literature that was referenced, though informative and worth reading, they are full of errors and opinions, once again, from the European perspective. If anyone truly is interested in a complete understanding of a craft, they must read from all perspectives of the host culture. Better yet the people doing the craft today.

I won't even start about the realities of oblique vs horizontal frame stiffing methodologies as they were eluded to in this post thread.

Respectfully Submitted,

Jay C. White Cloud