Timber Framers Guild Forums Tools Timberframe Design Mortiser and Tenon?

Hello,

I have several round and square post to instead/attach to round beams. I am new to the log home so I am not too familiar with attaching them. Could someone please explain the best way to make a mortiser in a round log beam and a tenon in a round/square log post without a chain mortiser?

When we wanted to bore a hole into a round piece of wood we used a boring machine, and we created a set of blocks on either side of the round piece for the machine to rest on. This held the machine and piece so that we could bore the hole and then chisel it out to make a mortise.

Here is a snapshot of the setup:


You could do the same think with a longer piece you just have to create a set up so that you have a flat surface to reference off of for the machine to sit on, that is 90° to the mortise holes.

I hope this helps you to understand how you could create a mortise into a round piece of wood.

Jim Rogers

Set the log up so that your mortise will be plumb, take a drill and rough out your mortise. You could attach a bullseye level to the drill to help out. Then clean out the rest of the mortise with a chisel. Use a torpedo level to check your sides.

As for the tenon... if you are comfortable using a chainsaw you could cut the tenon all with a chainsaw. If not, break out the handsaw. Now if the post is square then you can use a circular saw all the way around the tenon.

the mortise can also be cut with a chainsaw, IF you have the experience. I have done this a fair bit, esp with braces.
For using a free hand drill you can also screw a straight board on to the end of the log, that is parallel to the mortise. you will be able to use the board to sight the drill bit.

a chain mortiser can also be used, if you have one.
we regularily bolt our mortiser to a plywood base to do stuff like this.