So if you are following the 6 posts, 12 rim joists and 12 braces have been rough cut and sized. Then the braces had the tenons cut. Now it is time to cut the mortises into the posts and rim pieces. If done correctly it will be a nice fit forming a hexagon rim with 6 posts held by 12 braces at 45 degrees. And this is what it will look like.
Here is the fit of the brace to the 3” by 6” rim joist.
And here is the fit to the 6” by 6” post.
So how do we do this ?
Let’s start with the mortise into a post. After determining the location for the tenon it has to be layed out. Now because this is a hexagon the holes need to be drilled at a 30 degree angle.
The 1 - 1/2” diameter bit was guided with this drill guide. Notice the marking rings on the drill shank. Yellow for 1”. White for 2 - 1/2” and Orange for 3” depths. Very important!
The blue lines show the depth of each hole in profile. This is used to control and assist in getting the correct 45 degree angle needed for the tenon. The chisels will do the work to remove the unwanted wood left after drilling.
The 3” deep holes need to be drilled at where the end of the brace meets the post or the rim joist. So in this picture the brace would be slanting down as it should be with the construction being up side down like I’m doing it.
You have a 50/50 chance of screwing this up if you’re left handed like me. And I did just that on my second set of braces. In this picture the post (not shown) is on the left. Meaning that the brace would be slanting up. Thankfully I caught my mistake at the last minute. But this will haunt me for the next 4 posts and brace sets.
If it can go wrong, it will, be prepared. The screw point came out of the drill.
Did I mention the 50 degree angle that needs to be cut for where the brace meets the post? You can see the compound angle that is formed as the brace folds in the wood a relief angle needs to be cut.
Compound angle between post and brace.
I had to build a “contraption” since I had no helper to hold the 6 by 6 after I removed the temporary 1 by 2 braces.
The engine hoist secured the post end but allowed movement and adjustment after the temporary braces are removed.
Once the braces were fit to the posts and held in with a single screw it was time to get the exact location of where the brace mortise needed to be cut into the rim joist.
Now I know this could be looked at as cheating but I think of it as using your head. And it worked like a charm. In the normal way one would use a square and measure down and over. Or a real pro would just use the calculations from the brace layout. But you have to remember this is rough cut timber and not dimensioned planed lumber.
With the post plumbed.
The exact distance for the location of the mortis was marked into the rim joist for each brace.
After laying it out correctly and drill it out correctly then the 45 degree angle for the tenon was cut.
And this is what you get. One more post and brace pair to go tomorrow.
So what’s next? Disassembly and setting the roof rafters.
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