Well said, all. Yet I can't resist!
IMHO: Square Rule is the means by which we layout and cut a "perfect" (dimensionally accurate and square) timber frame from "imperfect timbers". Reductions and dimensioning from a reference edge are tools that compensate for dimensional variations in timbers (i.e. an 8x8 that's 7-7/8 X 8-3/16 gets reduced to 7-1/2 X 7-1/2 AT THE JOINT.) This ensures that your reference edge-to- reference edge dimensions are correct. When a timber is straight and square, laying out from an edge will be sufficient to achieve this ("edge" rule or "mill" rule, I think of this as sort of a subset of square rule).
If the edges or faces are not straight and/or square we need to establish straight and square planes to use as references. This is when we snap lines on the stick to define these planes. I've heard this called "snap line square rule" or "true square rule" or just "square rule" as opposed to "edge" or "mill" rule.
I think most of us are on the same page but we have the usual vernacular differences. He calls it a wind brace, she calls it a knee brace. (***Not intended to start a discussion on different kinds of braces!***)
There you have it. Fee: $0.02 (waived)

Hi all,

here is something that is bothering me. If one works with old beams or hand hewn beams you would ecpect them to not be square and/or straight in which case square rule would be applied.

Now if I am ordering beams from the mill and have size variations of up to 1/2" than I wonder why we are using saw mills in the first place.
Remembering back in Germany. If we ordered say a 10x20 (4"x6") than we received a 10x20. You could measure it whereever you wanted it was always 10x20. And those beams were not cut on a fancy mill. So does that means the saw mills here are so crappy or is it the mill operators? I doubt the beams would shrink that unevenly in a short period of time.

Maybe this should have been a seperate discussion but when I read Dan's post I could not help but ask.

Being a sawyer, I try as best I can to make sure my timbers are within a 1/8" tolerance. But wood can move while milling, and even though the mill and blade travel in a straight line the wood can shift in even the best of mills. This shifting can cause the timber to be of different sizes from one end to the other.
Being careful to read the log and watch for stress being relieved and making the cuts in the right order or on the right side to compensate for stress relief is an important part of being a sawyer.
Doing this correctly is important.
Some sawyers sit in a booth and don't get that close to a timber to notice that it has shifted due to stress.
Personally if your timber are out 1/2"; I'd have a serious talk with your sawyer or lumber supplier and let them know this is un-acceptable. Or find another sawmill....

Jim Rogers

I agree with Jim, sawing to 1/8 or 1/4 is good quality sawing, and produces timbers that will be useable for timberframing. Wood definitely moves as you saw it.

EH, are the timber rough-sawn off the mill, or have they been planed? The big circle mills are less accurate than the small bandmills like Jim Rogers and I run. They are designed to pump out the lumber in a hurry. This is why a 2"x4" is actually 1.5"x3.5". That way they can have a large margin for error coming off of the mill and just plane it down to a consistant size. When I saw out an 8"x8", it is usually right on, unless I miscalculated the scale reading, but it takes me a lot longer to make it than a circle mill.


Dave

In my week long introductory timber framing class last week, they called out method square rule. The project timbers we used were very nice, planed, and accurate to within 1/16th or better. The also had very little crown (bow?). We marked our outside face and the top as our reference faces and made all measurements from those faces. This makes sense so that you are basically using the same face of all the timbers of your bent as a reference plan and therefore all measurements being made from this same plane will assure that the mortise and tenons align to this plane (and the top reference plan. Then as long as you make the other two faces of the mortice or tennon square and to the correct dimension, it will all fit together correctly. From reading this post, it sounds like mill rule and edge rule are the same thing just a different name. Is that correct?

what i don't understand is how one can project a perfectly square and lengthwise true shape into a non-perfect piece of wood from one edge. this is what sobon seems to suggest in his book as a way of dealing with hewn timbers. but where do you lay thearm of the square? if that one outside edge you layout from is not perfect, then your 7X7, though it may be a perfect square, may not be aligned along the length of the tree.

the only way to do it exactly seems to be with chalk lines. and even they are a little fuzzy.

the reference has to somehow remain a perfect, symbolic abstraction through the whole process- i.e. map out the ends of the log with vertical and horizontal axes- ideally the center of the tree- use this to square the timber, assume that the timber is neither square nor straight, refer back to the central axis to lay out chalk lines, and use a standardized measure to layout joints from those projected lines.

and then a check opens up 1/16 of a inch and the timber is that much wider.

Hi all;

In the old text books to "take a timber out of wind" (as in winding) they instruct the tradesman to re hew the timber so that you have 2 square sides, and then placing the timber on trestles and blocking it from movement, you would continue to smooth off spots along the length of the timber to coincide with the position of the each mortise location, using a square and straight pieces to sight over on each end of the timber.

This does work amazingly good in practice, and will allow you to utilize timbers that are quite twisted and that have long sweeps.

"It is always good practice anyway to hew or broadaxe timbers oversize to allow for adjustment such as that above should the timbers move in the drying process that usually occurs during the time that the timbers are being readied for the carpentry to begin."

The above instructions appear in a book written by Willam E Bell in 1858 titled "Carpentry Made Easy"

You will also notice that timberframing is referred to as "Carpentry" not timberframing as we refer in our modern world.

NH

I am just a newby and I have a rather large pile of oak timbers just beginning to find a new existance in a TF addition to my home. On paper everything can be calculated in theory, but when you pull out a timber as I did last week ( for the first time ever) you very quickly find out that the timbers are not even close to the perfect wood you want. They have distortion from he time when they left the mill ( bandsaw) cut by an excelent sawyer. They were stacked and stickered but still checked and distorted over time.
In my case I started with a bent girt and two posts. For reference I chose the top center of the bent girt as my reference and made that level ( or vertical plumb as the timber is on it's side), and then marked the tenons level and on center as best I could. I housed the un-square end of the girt in the post when now I see I could have squared up the girt end first.
on future similar connections I think I will do this.
Very interesting discussion on this topic. I would like to learn a bit more about Japaneese framing techniques who seem to enjoy the challenge of working with timbers that have almost no straight lines anywhere except perhaps in the joint itself.
Any reference books to suggest?? Dave (in NJ)

Hi Dave,

A good start point would be to read "Building The Japanese House Today" by Peggy Landers Len Brackett (ISBN 0-8109-5931-3) which will provide all the inspiration that you need to strive to achieve excellence in your own work. Len's daughter Aya has provided stunning photographs of Len's work in the book.

For specific layout and cutting techniques you would do well to consult Timber Framing Nos. 26, 28 & 29 where Michael Anderson discusses and illustrates Simitsuke - Koya Gumi (marking) plus Michael also featured again in TF 39 & 40 where he discusses the Japanese timber framed building traditional practices.

My son visited both these guys in California earlier this year and came away much inspired by their competence in the field of Japanese framing and lifestyles. As I write the scent from a piece of Port Orford cedar hand planed by Len dilicately scents the air of my office.

Breathe deep and strive for perfection !

Regards

Ken Hume