Purpose of pencil line when cutting dovetails
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When Paul is laying out his dovetails he uses the thickness of the other side to draw a pencil line. Once he cuts the angle of the dovetails, he then goes back and does the same thing but uses the knife to make a knife wall. Why doesn’t he put the knife wall in at the very beginning instead of using a pencil? This seems like double work.
maybe an example of the ‘measure twice cut once’ technique?
The pencil line is a guide to help when laying out the tails, and when cutting the tails. The mating part thickness is then knifed in, and the knife line is put only on the waste areas / inside of the joint where it won’t be seen. Some woodworkers will knife all the way around both pieces, which some say helps to indicate that the joint was cut by hand, but which can also take a bit more cleaning up than a pencil line would
Colin, Czech Rep.
In some videos Paul has explained he is using a pencil to make it easier to see on the video.
He has a video specific to the knife wall. in his video on the knife wall technique he explains he considers the pencil line rough layout and the knife score more definitive. And he makes the distinction between just marking and establishing the wall that guides the saw.
Note in the ideó that when he makes a dado he doesn’t make the second knife wall until he can establishe the board position by removing some of the waste. To register the board that goes in the dado.
Thanks for the replies. Sometimes when I’m cutting dovetails I get ahead of myself and put the knife wall in instead of the pencil line. Then I cut the dovetail angles. Then I go to flush the side piece and add the knife wall only to realize I already did it. It seems to me that this wouldn’t compromise the fitting of the joint.
This shouldn’t alter the fitting of the joint. You will though have the knife line appear in the final piece or having to plane it off afterwards.
What I do is skip the pencil line across the board, laying out the tails with long pencil lines. Then, I do the knife wall (with a cutting gauge) cross the board around the tails on the outside face and across the whole board on the inside face. I’ve previously laid out the pencil line a bit off from where the knife wall ended up being and it didn’t help, so I just don’t nowadays.
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