How do I install this knee brace to my pergola post?

Question

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 ?

I was hoping to use a through bolt here too, but can't figure out how to create a surface to hold a washer to the angled face of the brace. Any suggestions?

Answer 1

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.

Answer 2

And another option would be to use a beveled washer. I would use a dado for all of the joints in all of the answers just to avoid slippage strain on the bolt/wood interface.

Answer 3

The simplest way is to recess the washer and nut into the angled brace.

1. Using a spade bit slightly larger than the washer
2. Mark where you want the hole.
3. Start a hole in the right side face of the brace, perpendicular to the face of the wood.
4. 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.
5. Drill only deep enough to bury the bottom edge of the bit in the wood.
6. The bottom of this hole will now be parallel to the opposite (left) face of the brace.
7. Change bit to one just larger than the body of the bolt.
8. Continue to drill through the brace and then through the upright post.

Answer 4

Minor variation to recessed holes, if you don't have or don't want to buy a spade or Forstner bit: cut a flat face into the angled support. Ensure that you leave at least 50% of the width of the angled support for strength.