A perfect cut is both true and clean. Here’s how you can achieve it with a plain-old circular saw.
Don’t rely on your eye for anything longer than six inches. To keep a short cut straight, position yourself so you can see the blade cutting along the line. For longer cuts, use a cutting guide. This is a straightedge clamped to the material you’re cutting. Keep the saw’s baseplate tight against the straightedge and flat to the material, and move the saw smoothly. If the blade wobbles, you may chip the material.
Some other ways to reduce chipping or “tearout” when cutting across the grain:
Use the right blade and keep it sharp. A 40-tooth carbide blade with triple-chip grind is good for hardwoods, particleboard and plastic laminates, while a 36-tooth or finer alternate-top-bevel blade will cut plywood well.
You can cut wood “good side”-down or:
* Score the cutline with a sharp knife.
* Lay a strip of cheap (ie. not too sticky) masking tape along the cut area, draw your line on it and cut. After the cut, pull the tape away perpendicular to the cut.
* Make a plywood “shootboard”, which protects the surface from the baseplate and holds down the wood fibres.
Preventing kickback: This occurs when a circular saw blade binds in a cut. Still spinning furiously, the motor forces the blade to climb out of the cut and… look out! To avoid this, at least one manufacturer recommends first tightening the nut that holds the blade, then backing it off slightly. Torque varies for different woods, but when you get it right, the blade stops when it binds… even though the motor continues to turn. Check with your saw’s manufacturer before trying this.