Brace pocket layout

[Dan_Shade]

@Jim_Rogers

Can you refresh my memory on brace pocker/mortise layout? 

What is the difference between line A and Line B in the photo below? 

[Brad_bb]

Is that your 45 degree angle cut?  Are you laying out with mill rule or square rule?

[Dave Shepard]

A is the backnl of the mortise. B is the 45 degree mark.

[Ljohnsaw]

What I see there is a 45° cut will go down from B to A. The upper rectangle on the edge of the beam/post will be the housing (1/2"?).

The pencil writing that is upside down looks like 3 + H, for a 3" pocket depth plus the housing.

I add one additional line that shows the bottom of the pocket where the 45° meets. That would be right around the H. This allows me to layout where I want to drill down to full depth to remove as much material as possible before I chisel.

[Dan_Shade]

Square rule 

[Dan_Shade]

[Jim_Rogers]

What I see there is a 45° cut will go down from B to A. The upper rectangle on the edge of the beam/post will be the housing (1/2"?).

The pencil writing that is upside down looks like 3 + H, for a 3" pocket depth plus the housing.

I add one additional line that shows the bottom of the pocket where the 45° meets. That would be right around the H. This allows me to layout where I want to drill down to full depth to remove as much material as possible before I chisel.

John is correct the "A" line is the bottom of the 45° slope and the "B" line is where it comes to the surface of the timber. 
Also, correct is that the mortise is 3" deep plus the housing depth. Which can vary depending on the actual thickness of the rough sawn timber.
Jim Rogers

[Brad_bb]

I think Jim must be busy teaching a class, wait, there he is, he just posted. 

I don't mean to side track this discussion.  But Dan_Shade's picture looked like a good one to give an example of housings.  I find a lot of new people confused by housings.  They talk about making a 1/2" housing for example, but many times don't understand that you are actually not measuring and marking a 1/2"  Housing.  1/2" housing is based on nominal dimensions.  So if your timbers are true 8x8's, and the width of your timber is exactly 8", then your housing will end up being 1/2".  But if your actual timber dimension is more or less than 8", the housing depth will vary accordingly.  I hope you don't mind @Dan_Shade If I borrow your picture for this example? 
For Dan's picture, I envision it being this part of a bent:


In the photo you can see where I drew the Arris(red Triangle). This is where the two reference planes meet.  The outside face of the building is usually chosen as a reference because it has to be flat for receiving sheathing/wall framing etc.  B is the location of the bottom of the mortise on every post.  On every post you measure from the outside wall, which is the reference face, a fixed distance to draw the bottom of the mortise.  Likewise A is the location of the housing face.  This is a fixed dimension and is always measured from the reference face like B was. If the width of the post were perfect at say 8", then the housing Depth C would be 1/2".  Keep in mind that you'd never measure or layout C, but rather you layout A.  The bottom of the housing was defined by A.  If the actual post width was 7-7/8", then your housing depth would be 3/8".  If the actual post width was 8.25", then the housing depth would be 3/4".  The point is, the depth of the housing is not something you measure, but rather defined by the actual width of each post and the fixed distance from the reference face.  This fixed distance is based on the ideal timber within the timber that we talk about in square rule.  Since all of your housings are the same depth based on the exterior wall reference, that means that every brace in each of these identical bents will interchange. 

If you measured and cut a 1/2"  housing from the inner face of the posts, every brace length would need to be different, assuming the pocket on the tie beam were in the correct location.  That is why everything in square rule is measured from a common reference face, so that it's consistent.

This is a very tricky thing for newbies to wrap their brain around sometimes.  It was for me for awhile.  I was confused about the "perfect timber within the timber" for awhile.  I just thought Dan's pic looked like it would show this well.  As the timbers vary in width, then C will change by that amount too, but you don't need to measure C.

Is this easier to understand?  Anything wrong with it?