Any motivated woodworker has read the advice usually given about re-sawing. Unfortunately, the advice commonly disseminated is incomplete. This often happens when experts, who forget what it's like not to be experts, offer instruction that is built on assumptions.
This post will give you information you've NOT read elsewhere. If you've done everything "according to Hoyle" and still found yourself upset and frustrated, I think you'll find it particularly helpful.
To prevent confusion and clarify some basic facts, here are a couple of things you need to know in advance: (1) I use a 14" bandsaw with a riser block. (2) I use a 3/4" wide Timber Wolfe re-saw blade (3 T.P.I.). Most of the workpieces I re-saw are several inches high, 24-30 inches long, and about two inches thick. My re-sawn pieces vary in thickness from 1/16" to 3/4". (3) I use a shop-made, flat guide fence, not the kind with the pivot point. The fence is about the same height as the workpieces I re-saw. (4) After ensuring that the table and the fence are both at 90 degrees to the blade, I clamp the fence to the table, following the "drift" line which I've marked on the table in pencil. (5) I make all adjustments to thrust bearings, side guides, etc., both above and below the table, after the upper blade guard/guide post is set at the appropriate height. (The order of operations makes a difference.)
RE-SAWING TECHNIQUE
Faulty technique causes two cutting problems. Trapezoidal cuts result in a finished product is wider at the top than the bottom or vice versa). Trapezoidal cuts are a special problem when re-sawing tall workpieces. Cuts that are uneven along their length result in a finished product is wider where you started cutting than at the rear, or vice versa).
To prevent these problems, observe these cautions:
1. Be aware that as you feed the workpiece, there are two sets of forces being applied to it. One set is a “forward” push (like feeding wood into a table saw blade) that moves the workpiece into the blade. This force determines how quickly you cut. The second set of forces are “lateral”; these keep the workpiece flush to the guide fence. Most problems develop when too much pressure is applied laterally.
2. When feeding any workpiece, but especially a tall one, how you use the push-block that helps keep the workpiece flush to the guide fence (lateral forces) is critical. Exert firm but not very heavy pressure evenly across the “top-to-bottom” face of the workpiece. If you push too hard, or if the force you exert is above or below the center point of the workpiece, a trapezoidal cut will result.
3. For cuts that are straight along their length, the “front-to-back” location of the pressure exerted with the push-block to keep the workpiece flush to the fence makes a huge difference. If lateral pressure is applied on the “fore” side of the blade, the cut will go off and you will wind up with a tapered end product. If lateral pressure is applied on the ”aft” side of the blade, the cut will go off in the opposite direction, but you'll still wind up with a taper. To prevent this, apply pressure only at the point at which the workpiece passes through the blade. In other words, lateral pressure should be applied only where the blade intersects the workpiece.
4. To ensure that the blade is cutting exactly as you want it to, use your eyes, and also gauge the strength with which you are applying pressure(s) on the workpiece. If the blade wanders, even a little, stop immediately. If you do not stop, the situation will only worsen. After stopping the machine, figure out what is going on and why. Then correct the problem. Most often you'll find it's an error in either where force is applied, or how much force is applied, or both.
If there is sufficient interest in this post, I will make a video and post it here.
