Help!!! Tongue and Fork Joint on Rafters

[Joel Eisner]

 :P 

I finished the girts with their multitude of joints and now it is off to 5 sets of rafters.  I was working on the first bladed scarf joint.  They are 8x8 SYP timbers with a bladed joint at the peak of each bent.  The blade portion (tennon) is 2 inch thick and centered on the corresponding rafter. 

What is th best way to get the material out of the other rafter where the blade is going to fit (mortise).  I do not have a 2 inch auger bit and with a diagonal cut through the timber it is a long way to chisel out. 

What about cutting the sides of the mortise with a circular saw/ hand saw and and then remove the majority of the waste with an elec chain saw, with final clean up using a long chisel and slick?

Any other ideas?

[Jim_Rogers]

I believe you're using all the wrong terms.
First of all a joint that joins two timbers at the ridge isn't a scarf joint.
A scarf joint joins two timbers that are in line with each other from end to end.
A "blade" as you're calling it is the tenon or the tongue if you're doing a tongue and fork joint.
The mortise is called a fork if it's open to the end of the timber, it's called a mortise if it stops before the end.

As to the method of removing the wood in the center of the mortise/fork your method is ok to do.

Normally we do bore a hole at the end of the mortise/fork and saw down each side of the open fork to this hole to remove the most wood by the easiest method.

Then pare to the line with a slick or wide chisel.

Trim as needed to fit pair together.

Good luck with your project.

Jim Rogers

[ARKANSAWYER]

  When cutting out a fork you can use a smaller drill bit.   You can take a 3/4 drill bit and go down each side of the fork.  Cut in each side with a chisel and you should be able to snap off the piece of wood.  Then clean up the middle.