Lead angle refers to the direction the wood needs to move in so that the bandsaw blade cuts in a straight line. Lead angles are to bandsaw blades what fingerprints are to fingers. When it comes to bandsaw blades, there is a tremendous amount of variability. Even with blades that are made with the same machine and same band stock coil, a perfectly fine blade can be expected to lead up to 1/2 inch from parallel to the miter slot of the saw. Then the next installed blade might lead that same distance out but in the opposite direction.
Of course, as long as you end up with good results, it really doesn’t matter whether the wood is fed northwest or northeast. Even strange lead angles only cause trouble when you try enforcing your own preconceptions on them.
Whenever you are making a freehand cut over a straight line that you have marked on a piece of wood, you need to determine the lead angle while you are working, and adjust the direction of your feed back and forth as your blade starts to wander off its line. Eventually you will zero in on the direction that allows the blade to consistently follow the line. That is a fairly accurate description of a resawing stock control technique that is commonly employed where a point block fence is used.
A radiused point block enables you to keep the stock in a vertical position, but the feed direction is left completely up to you. This is an efficient method to use for resawing one or a few pieces of wood: first mark a line where you want to make your cut, and leave yourself a large margin for error. Next, set your point block to whatever width that you have marked.
Closely watch the cut, and adjust the feed direction as necessary in order to follow your line. You will tend to waste a bit more wood using this technique. However, the advantage is that setup is minimal. Point block users with a lot of experience are able to make consistent cuts without wasting a lot of wood. However, for many sawyers using a straight fence might be a more practical way to go.
Straight and Narrow
Whenever you have a number of pieces of wood that need resawing, you can do this efficiently, repeatedly and accurately using a straight fence that is precisely tuned to the lead angle of the blade. Start as I described above and make a freehand cut along the straight line. After you have started to saw down the line, turn the saw off and make marks with a pencil on the saw table along the stock’s edge. Then set your fence according to the marks.
Next, make your resaw cut, either with the work at hand or a short scrap that is approximately the same width and hardness. Start off your cut gently. That way the initial impact will not begin the cut wrong by twisting the blade. As you proceed with the cut, watch closely to make sure the stock doesn’t start to wander from the back of the fence. If it does, stop your saw and adjust the angle of the fence as needed. If the wood remains tight up against the fence, and your saw starts to labor, then stop what you are doing and ease the fence’s rear away from the piece of wood.
Take Your Bow
Once you have completed the cut, place a straightedge against the board’s resawn face. Unless you happen to get very lucky, you will notice that the saw blade bowed right or left in the stock. You understand that a blade’s solid body can’t just move sideways through a piece of solid wood. In order to make a bowed cut, the blade’s teeth must lead left or right within the wood (there they are free of the constraint of the lateral guide), then the blade must be twisted so that it saws way outside of the vertical.
In order to keep your cut vertical, the fence must be adjusted to match how the blade is twisted. If it bowed to the right, then the rear of the fence needs to be adjusted to the left slightly; if it bowed left; then the fence angle needs to be reset at the rear slightly right. Make an additional test cut and then check the wood’s face once again.
It could take up to three to four tests before you’re able to get your fence set properly for flawless sawing. However, once you have done that, you’ll be able to resaw identical piece after identical piece, and your cuts will be so straight that all it will take is one pass through your planer to produce flat, clean wood at the thickness you have targeted.
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Ted Leger –
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