The Kohnen Scarfing Jig

Randy Torgerson

Back in January, John Kohnen and I were discussing scarfing jigs and I showed the jig I used on my table saw.  John said “I've been thinking about a jig (or would it be a fixture? I never can keep that straight) for using a handheld circular saw, so I don't need to clean such a wide behind the tablesaw” 

I have been under house arrest these last few weeks and I have not been allowed to work on the Tolman so I am working on the long neglected Puddle Duck Canoe. 

I will need to scarf some parts for the gunwales so I decided to build the Kohnen Scarfing Jig.   The jig would use my track saw and be portable so I could take it to RiversWest to cut the splash rail for the Tolman.  The jig cuts a 1:8 scarf for material up to 1 inch tall and 1 inch wide.  Since I cut both pieces at the same time the jig opens up to 2 plus change wide.  This was arbitrary since and I can change it in the future. 

The design goals were to:

1.    Not hurt myself
2.    Not hurt the blade by cutting any screws. 
3.    Easy to setup.
4.    Keep myself busy.

I jointed some four foot long 2x4’s on two sides and then planed the boards to 1-1/4 thick.  Two of the 2x4’s will be put on the bottom to keep the jig together in case the plywood was cut though and to allow space to clamp the track to the jig.  I jockeyed the track around and found that 12 inches by 45 inches was the best size for the plywood. 

I screwed the two support 2x4’s on the bottom and then worked out the size of the clamping 2x4’s should be 28 inches.  One of the clamping 2x4’s is screwed to the jig and the other is held in with clamps but I may use wedges in the future since I can now easily cut wedges quickly.

I clamped some scrap in the jig and gave it a whorl.  As you can see from the pictures the jig worked very well.



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