I am trying to lay out 32' hand hewn timbers, and I'm worried about accuracy.I have read the section in Jack Sobon's book but don't quite understand. Any help from the Experts would be appreciated. Thanks, John..

Hi John

It would be very helpful for you to be more specific in your question. What exactly is not clear?

All layout solutions come from control of horizontal and vertical lines, planes and dimensions. Your framing square models hor. and vert. Your spirit level and plumb bob detects hor. and vert. You reference to hor. and vert. in sqaure rule by choosing adjacent square sides as layout faces. In scribe rule you orient and bench mark the timber to hor. and transfer dimension by plumb line projection. Your tools must be accurate. The former statements are the first princples.

Please restate your question lest you get a filibuster.

Roger

hello John:
here is a topic that really interests me, and one that I am quite familiar with.
Working with and doing layout on hewn timbers is a time consuming and skill testing proceedure. It also requires a fair amount of perseverence even by someone that is already a good tradesman in another facet of timberwork.
One of the first requirements is to work very accurately, and by this I mean every move is dedicated to as near perfection as possible, if you strive for this you will not have any problem turning a rough hewn surface into one with motises that will accept tenons and seat out nicely.
I suggest putting only one main chalk line on each of the four surfaces using a fairly fine grade of line for this purpose. Before you start to put on reference lines though I suggest that your work horses\supports are placed fairly level to one another, and then placing the timber on top with the outside surface facing up. Check the timber for wind, and if wind is evident with shims\wedges split the wind so an equal amount is shared by both of the timber's ends. You are then ready to strike a plumb mark on both ends usually 4-1\4" from the outside of the timber, using a level and a sharp scratch awl. When you eventually strike a chalk line from end to end on both upper and lower surfaces, this line will be along the inside of all the mortises, and should be accurate providing that you take precautions to snap the line accurately. The next step using a square on the ends again laying the blade along the vertical scratch mark, and down again 4-1\4" from the upper surface scratch cross marks on both ends. Complete your chalk lining on all 4 surfaces, and you are ready to do layout of mortises along these lines. At this point you are just getting started nicely, and you should have a good understanding of the measurements and location of all mortises their orientation on each timber, what braces are involved. Always remember and place the timbers in the same orientation order before beginning work on each one. I usually number each timber and record it on a work sheet for referral, you will need this important information eventually for assembly. I use dummy tenons to test the mortises as I work along, and feeler guages made of 1" pine to slip over the tenons as they are cut out and shaped.
Good luck, and have fun, I am here if you need further help or advice, I am sure that others will also, there are many good framers out there
the NH

Roger, The four timbers that I am cutting are wall and purlin plates. The bottoms will be morticed for the wall and queen posts and braces and the tops will receive step rafter seats for comon rafters. In Jack Sobons Book ,(Build A Classic Timber-Framed House)on page 77&78 he talks about First level and plum the two layout faces. He then holds the 1 1/2 tongue of a square against the end of the timber and sights down the top raising the square up or down then draws a line under the tongue. He then draws the perfect timber on the end and repeats this on the other end. He then snaps chalk lines down the faces to connect the perfect timber layout on the ends. So if I understand this method all layout for the joints are layed out from the chalk lines..?? Any Help or comments would be appreciated, Thanks, John.

Hi John and Hewer

I don't have the Sobon book, so I will outline my approach to the problem presented. I will be brief since this is my break between tasks.

I personally have gravitated away from chalk line dominated layout, if you prefer to use them white chalk and red ink are less bold on the finish product.

Lets say you have a 8 x 10 x 32' wall plate, four bents, housed braces and stepped rafters. I would place plate stock top up on sturdy level horses. Balance the wind, shim securely and clamp. Assuming slight crown and sweep, ignore crown and sweep. Mark bent centers on top of plate, over all four centers plane out a cross grain level station from edge to edge with jack or scrub plane. Mark the outline of the level and place tick mark for reference side. You have now established top plate level reference cut into wood. Turn plate on side, register square to level station mark 9.5" for post top reduction at all four level stations. Place 12 foot straight edge over 9.5 marks and score reductions at post and brace locations. Also score along top edge from level station to station, I order to level rafter seats. Turn plate to opposite side and repeat. You can mark the staight edge with approximate post and brace dimensions to keep marks in the right place.

You should now have control marks scored into the wood. I have found that scoring has quickened and solidified my work process. Anyhow, proceed with joint layout along the length. Got to go for now

Roger

To continue...One advantage to the chalk line is that you have good registry for the framing square. The alternative is the eye ball method. Suppose you have a timber that has an uneven surface, you cannot register the square on the side of the timber. Place the square with the long leg on the flat surface with the outside of the square roughly aligned with the side surface, sight down the square and align to the shaft. I have squared around some nasty stuff using that method.

The important thing to remember is that all workable and repeatable method (square, scribe, mill, jigged bench or CNC whether numerical or relational) operate under the same set of rules, albeit expressed differently.

Roger