Timber Framing a hexagon

[Woodsende]

Anyone ever timber frame a hexagonal shape building/pergola? Any thoughts on how to do the joint? I am looking at 6x6 posts with either 6x6 or 4x6 eaves. There is a 120 degree angle between the two side pieces, and it will be resting on the 6x6 post.

I have a Makita chain mortiser, but it is set to clamp to a beam and cut parallel to the grain. Not sure how to use it for the 120 degree offset (safely).

Robert

[Ljohnsaw]

Are you using "off the shelf" timbers from a big box store or will you be milling up your own?  If doing your own, why not just make hexagon posts and then you can use your chain mortiser on the flat surfaces?  If using off the shelf posts, then I would think you would need to make housings at the appropriate angles.  Take a 15° cut off of two adjoining faces of the perimeter posts to open up the 90° angle to 120°.  For a center post (assuming there will be one?), you will need to make it hexagonal where the beams will meet.  And I would assume it would need to be a big post to house all of that.

If you are just doing regular posts and need to make the angles with the chain mortiser, make a hollow box to slip over the post end with the appropriate angles built into the box.

[Woodsende]

I am using square posts. My most recent thought is to use the mortiser on the posts, and angle the tenons on the beams at the appropriate angle to intersect the post. Use a full housing for the beam to make it stronger.

[Jim_Rogers]

I am using square posts. My most recent thought is to use the mortiser on the posts, and angle the tenons on the beams at the appropriate angle to intersect the post. Use a full housing for the beam to make it stronger.

not the best idea as the tenon will/could be cross grain. I would cut the post to the angles so that the tenon enter 90° to the post surface. like a regular joint.
I've cut post so that this could be done before.
Jim Rogers

[julian3rd]

Here's a jig I built for the makita chain mortiser for a hexagon gazebo of cypress last year.  I left the posts square... and Jim is right, there is the issue with cross-grain on the tenon.  I made the mortise/tenon on mine larger than usual to compensate.  Gazebo's successfully holding up a couple tons of slate...
 

 

 

 

[Woodsende]

Do you have more pictures of the jig you made?