Very basic question about sawing to marked line
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10 November 2017 at 10:06 am #361657
I have been watching the tool chest episode 1. While cutting the dovetails, Paul, first layout the joinery with a pencil. At this point, I can say that I should cut the tail on the waste side of the pencil line so that the line is fully visible. Then he proceeds with the marking knife by saying “right on to my pencil line (min:16:40). My question is shall we make that cut with the knife in the middle of the pencil line or shall we position the square and cut with the knife on the waste side of the pencil line so the knife cut is actually next to the pencil line? Since while sawing, handsaw rests on that knife wall, if I make the knife wall “right on to pencil line” I would be cutting the pencil line, thus the pencil line disappears? Am I getting this idea whole wrong or is there a cure for my craziness? If I can pass that point I know I will be the best carpenter ever 😛
Thanks,
CemFor the tails first method that Paul teaches, here’s how I think about it. The tails can be cut any way you like. You don’t even need layout lines as long as you saw square to the face and do not go past the shoulder line. Now, imagine placing the pins piece in the vise and laying the tails piece on top of it to mark the pins. All of the wood that you can see in the gaps between the tails are the pins. If you remove any of that wood, you will have a gap. All of the wood *under* the tails must go away; otherwise, you will not be able to close the joint. With the two boards lined up, you could spray the work with a can of black spray paint. When the tails board is removed after spraying, all of the black is where the pins are and all of the unpainted wood must be removed to make room for the tails. I would not want the saw to touch *any* of the painted wood. If I mark with a pencil rather than spraying paint, it’s the same thing: The pencil mark is *on* the pin. The unmarked wood must go. So, you must cut leaving the pencil mark untouched because the pencil mark is *on* the pin and the unpenciled area is the waste.
That’s how I think about it. Depending upon the wood, experience, and confidence that day, I leave more or less additional wood beyond the pencil line to deal with by paring or compression (some danger), but ideally the cut would exactly follow the line and exactly leave the line.
The original poster asked about more than dovetails. Every cut is the same…think about which side is the waste side and think about where the mark is going. It all depends. Sometimes the pencil mark is *on* the waste and is cut out. Sometimes it is *on* the “keep” side and it is kept completely. Even if you use a knife, you still need to decide this and make sure that you place the cut in the waste or, if you cannot, make the cut be light. I actually don’t like using a knife for dovetails because a) the mark is on the good part of the wood, not the waste and b) because it is end grain and knives don’t mark end grain very well. The first doesn’t matter so much in end grain because the knife will separate the fibers more than cut them, so as long as you aren’t totally crazy with the knife, there’s a chance that finish will absorb into the fibers and swell the joint closed (or glue).
Ideally, with a knife, your square is covering the wood to be kept and the knife is running *in* the waste. The cut is a tilted “V” and the vertical part of the V exactly defines the edge of the keep side and the slanted part of the V, which Paul calls the bruising, is in the waste. That’s why you must flip the square back and forth as you lay out (or must use some tricks)
10 November 2017 at 12:34 pm #361872Thank you Ed, that was a very definitive and meaningful explanation.
Glad it helped. After I posted it, I wondered if I, in fact, I take just the slightest bit of the line out since a zero clearance joint won’t actually assemble and also to leave room for glue swelling. This is something you need to play with for yourself, but the description, as written, seemed the clearest way to give the basic idea without that complication.
10 November 2017 at 6:47 pm #362479When cutting the second board (usually pins) the wood you want to take away is under the tails, so it has no marks on it if you are using the tails as a template.
Leave the knife cuts or pencil marks. They are on the wood you want to keep.
<edit> hmmm. Late response. It must have gotten stuck in the interwebs magic aether.
- This reply was modified 6 years, 5 months ago by Larry Geib.
- This reply was modified 6 years, 5 months ago by Larry Geib.
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