Reading Grain Before You Cut
Tearout is the torn, fuzzy patch that appears when a plane or a cutter lifts fibres out of the surface instead of severing them. It gets blamed on dull blades and cheap timber, and occasionally that is fair, but the ordinary cause is simpler: the cut was taken against the direction the fibres run.
Wood is a bundle of long cells lying roughly parallel to the length of the tree. They are almost never perfectly parallel to the faces of a sawn board, because the log tapered and the grain wandered. So on any given face the fibres emerge at a shallow angle, rising towards one end. Cutting in the direction they rise means the blade lifts them before it cuts them. Cutting the other way means each fibre is supported by the ones beneath it as the edge passes.
The practical method is to look at the edge of the board rather than the face. On the edge the growth lines run as long shallow arcs, and those arcs point somewhere. Plane in the direction the arcs are descending, not ascending, and the shavings come off in ribbons. If the surface still tears, turn the board end for end and try again before touching the blade. This costs ten seconds and solves the problem far more often than sharpening does.
Figured timber complicates this because the fibres reverse direction within a single board, sometimes several times. Curly maple is the familiar example: the shimmer is caused by fibres rising and falling in waves, and there is no direction that is with the grain everywhere. Here the answer is a very fine cut with a tightly set mouth, or a scraper, which works at an angle steep enough that fibre direction stops mattering.
The same reasoning governs machine work. A router bit spinning against the feed direction on a curved edge will tear out at the point where the grain reverses, so a curve is often best worked in two passes, each running downhill from the high point. On a table saw the issue is different, since the teeth cut across the fibres rather than along them, but the exit side of the cut still splinters, and a backing piece solves it.
None of this requires special sight. It requires the habit of looking at the board and deciding which way to work it before the tool touches the wood, and reversing the board rather than forcing the cut when the surface objects.