Although I haven't personally used chalk lines a lot. I believe the chalk line is laid out on a timber to some standard dimension such as 1" or more commonly 2" off the edge, so that the measurements can be easily figured. But someone who has had more experience with this should post the reasons why.

I was reading a TF book the other night about square rule and it said to put the chalk lines at 1.5 which is what the narrow side of the framing square width is. When reading that, I wondered if they meant that a tennon would have to stay inside the talk lines instead of going to the edge of the timber on each side. I'm not sure if that is what was meant, but I don't think so. I think they just want you to use the lines as measuring references to keep things square to those lines. If the distance from the chalk lines to the edges of the timber were not equal on each side, I think then that your tennon would not go to the edge, but rather would be centered relative to your inner timber(chalk lines) and the specified width of the mortise. Correct?

Which book are you reading?

Unless I'm mistaken the chalk line is just a reference line. It doesn't mean that this is the side of the tenon unless the layout is 1 1/2" off the true outside corner and then the mortise is 1 1/2" wide.
If the layout was 2" x 2" then you'd layout the mortise 1/2" off this 1 1/2" chalk line every where long this timber.
Does that make sense?

You are confirming my understanding Jim. It didn't specifically say those things. It's what they don't say that leaves me with questions. And the book won't answer my questions no matter how many times I ask
I'll have to get book name from home. It's one of the common ones. (I bought about 6 books based off the recommendations of Thomas Massie's blog).

Jim, that is correct about the chalk line being the reference line. If you have do use 1.5" of the reference corner and you have 3" braces that are 1.5/1.5 you could then just use the chalkline for one side of the mortise.

I did a little sketchup drawing but can't access my photosite. When that is up i'll post it.

Here is another problem that I am thinking about.

1. If you have a post and you decide to put the bow in. When you lay out your wall bracing on the post with this method your brace will sit proud of the post on the outside however much the post bows in. Then when you lay-out your bent brace connecting with the same post on the adjacent side, you would have an extra deep housing.

2. If you take the same post and put the bow out. The wall brace would sit shy of the outside of the post in the plumb plane. And then you might have to map a special bent brace to reach that same post because the bow is out.

Any thoughts?

mo

Mo, If I understand you correctly, you are thinking that the brace will be pushed further to the inside of the frame by the bow? That would only be true if you were using mill rule and basically measuring the depth of the brace mortise from the surface of the post timber that the brace rests against. With square rule as I currently understand it, you would measure the depth of the mortise from the reference chalk line(s), which is not bowed. You are thereby placing the brace into the timber relative to the "perfect" inner timber. You've created this perfect timber with your chalk lines, which you are measuring from, and you house your brace so that it's face will rest against a correctly positioned face(not the outer bowed face of the timber) which you create relative the "perfect" timber. It's all beginning to make sense to me now. Now I just have to get to practicing it! I plan to prep reclaim timbers in Feb and try to get a design on paper by the end of Feb so I can start layout in March.

I think Brad has a grasp of it now....
And mo you may have some points about the brace also.
But if the post bows in and you layout correctly you should have a deep housing.
If the braces is too long, it will show up when you do a fit up test with all the pieces of that bent. At that time you could trim the long brace back to correct it and make it work.
If the post bows out and the brace is too short then you'll have to cut another longer brace, possibly mapping as you have mentioned.
I would think it would be easier to trim a little off something that's too long then to have to replace the entire piece because it's too short....

Jim Rogers

If the brace is made to "print", and you've layed out the mortise/housing correctly using square rule, the brace SHOULD fit properly without any changes. As far as the brace is concerned, it should not know the difference if it's in a bowed rough sawn square rule post or an S4S mill rule post. The housing or respective mating face is in the same position in space in either situation.

Brad, As far as I am concerned you never lay-out from the inside face the depth of the housing for the brace. I can think of the only time when someone would do that and that is when a inner post has braces that meet on both sides. I personally would create a centerline down the post to lay these out. Even in Mill Rule the reference faces are used as references.

Now back to the curved post. Are you sure about not having to do anything to a brace to make it fit?

Here is a photo of square rule with straight sticks.


Now the problem with the bowed post.




In this situation if you were to use the patterned brace the nosing would be hanging in mid-air and there would be no housing on the post, in short too short. (Example: working 1/2" under nominal)

The only remedy I can see to fix this would be arranging your post with the bow in creating a deeper housing, or picking a different post that is straight damnit, or moving your brace in on your tie 1" towards the post and then work 5" off of your chalkline.

The idea of snaplines to me is access the simple line at the center of the timber. I place plumb and level lines on the ends of the timber. On an 8x8 timber for example the lines will be 4" from the reference faces on each end, on a 10x10 they would be 5".... The lines on each end will be level to each other.
Then the lines represent extensions of the simple line at the center of the timber.
To lay out a mortise or a tenon, I would use the snapline as the inside of the mortise/tenon on an exterior frame, or the center of the mortise/tenon on an interior frame.
Here is a sketchup model that uses snaplines, with centered m&t, as in an interior frame.