Accurate sawing starts with accurate layout which was covered in part 2, but there are several other factors that should be considered from body position to how the saw is held and more. For solid information on basic sawing techniques (and a whole lot more) I’d recommend The Foundations of Better Woodworking by Jeff Miller. What I will say here is that a moxon vise and properly tuned saw will make a world of difference.
A moxon vise raises the work to a more comfortable sawing height (your back will thank you). My moxon was made with the kit from Benchcrafted, but you can also get a more affordable kit from Texas Heritage. Your saw should be sharp, filed with a rip tooth pattern and a fairly high tooth-per-inch count, 15 is common. The set on the teeth also needs to be minimal, a couple thousandths on either side of the plate to ensure straight sawing. And when you clamp the board in the vise, align it vertically. If the board is tilted slightly hitting angles or sawing vertically becomes unnecessarily complicated.
Now lets get into it. When you start sawing across the end grain, sawing square to the front face is absolutely critical. A skewed cut will never yield a tight joint so you will either have gaps or have to do extra chisel work to square up the cut after sawing. This is okay, but chiseling takes extra time and adds another opportunity to make mistakes. What we’re shooting for here is saw-cut-to-saw-cut joinery. So how do you saw squarely to the face? Place the saw on the waste side of the layout line and lift the saw slightly. This means the saw teeth are only touching the far edge of the board and the saw can pivot around that point. Next, place the thumb from your off hand next to the saw plate and bias the saw plate against it. Using your thumb to steer the saw, align the teeth so they’re parallel to the layout line and start sawing with very light pressure. As the saw starts to cut into the board, lower the handle so you’re sawing straight across the board.
At this point the saw shouldn’t be very deep, just a light kerf cut squarely across the end grain. With this kerf established, focus on angling the saw to match the layout line and begin taking full, even strokes with the saw, not short, choppy cuts. I have found this to be an important part of saw-cut-to-saw-cut joinery. Full, smooth strokes means the cut can be finished in a few strokes, 4-8 is typical for most of my dovetails. This helps ensure a straight cut which is crucial. Short saw strokes means you may need 15-20 strokes to finish the cut… each time the saw may stray slightly. The kerf can also become enlarged which makes tracking the saw more difficult, so practice your sawing until you can fly through a cut smoothly and with confidence. A good way to practice sawing or just warm up for dovetailing is to run through several cuts on scrap wood.
Once you’re comfortable sawing to your line and squarely across the board, cut the sides of all the tails. I recommend cutting one angle first across the entire board, then go back and hit the other angle. This helps keep your muscle memory on track where as switching between angles can make it hard to get in a rhythm.
Before moving on, lets examine the cuts and understand what’s critical. We’ve already talked about cutting squarely across the board, but what about hitting the angle precisely? Well, having a straight cut matters, having that cut run to the exact angle laid out with the dovetail guide doesn’t really matter, it’s just for looks. In fact, you could cut the joint with no layout lines at all on the face, just cut squarely across the board and the angle can be whatever it wants. The reason to lay out an angled guide line is just to help keep the tails as consistent as possible, but it’s purely for appearance sake. For the joint to fit tightly you only need to saw squarely and in a straight line. Skewed cuts or wavy cuts will always result in gaps. The only other sin to avoid when sawing is cutting beyond your baseline. There’s really no fix for that besides wood filler.
Saw out the waste with a fret or coping saw (I opt for a fret saw) being careful not to cut below the baseline or into the tail itself.
The last step before moving onto the chisel work is to cut the waste off the edges. Flip the board 90 degrees (making sure to align it vertically again) and grab a crosscut saw if you have one. You’re sawing right against the baseline, so make sure to stay on the waste side of the line. One thing that can help is chiseling a small shoulder up to the baseline. This little valley gives the saw an accurate “kerf” to start the cut and leaves a super clean shoulder on the joint which will be visible when all is said and done.
Flip the board and cut the other shoulder, then it’s time to get out a chisel to clean up the baseline.