I have built a 7' x 13' pergola over my deck and have a slight wobble, so I intend to install some knee braces. Each post has two pairs of perpendicular beams stretching to the adjacent posts. For the brace-beam connection, a simple through bolt will be easy to do. But what's the best way to secure the brace-post connection ?
Prior to drilling the "through-hole", mark the location on both sides and use a paddle-style wood boring bit slightly larger than the O.D. of your flat washer, to make a large flat-bottomed hole.
Make the holes no deeper than necessary to make the nut, washer, and bolt end sit flush (you would need a shorter bolt).
For more precise creation of a flat-bottomed hole you could also use a Forstner style drill bit, but they are significantly more expensive than a paddle-bit. It depends on how nice and clean you want the hole to be.
The simplest way is to recess the washer and nut into the angled brace.
- Using a spade bit slightly larger than the washer
- Mark where you want the hole.
- Start a hole in the right side face of the brace, perpendicular to the face of the wood.
- As soon as the tip of the bit has a good bite, angle the drill until it is perpendicular to the opposite angle cut of the brace (the left face). Do this slowly and carefully, since only one edge of the drill will be making contact with the wood.
- Drill only deep enough to bury the bottom edge of the bit in the wood.
- The bottom of this hole will now be parallel to the opposite (left) face of the brace.
- Change bit to one just larger than the body of the bolt.
- Continue to drill through the brace and then through the upright post.