TPI stands for Teeth Per Inch. It measures how many teeth a blade has per inch of its length. Higher TPI (14–24+) produces smoother, slower cuts ideal for thin materials and metals. Lower TPI (6–10) cuts faster but rougher, best for thick wood. The TPI directly affects cut quality, speed, and chip clearance.

The Rule of Three states that at least 3 teeth must be in contact with the material at all times during cutting. This ensures stable cutting, prevents blade snagging, and reduces vibration. To calculate minimum TPI: divide 3 by the material thickness in inches. Example: 1/4" thick material → 3 ÷ 0.25 = 12 TPI minimum.

T-Shank is the modern universal standard used by 95%+ of jigsaws made after 2000 (Bosch, DeWalt, Makita, etc.). It features a tool-less quick-change system. U-Shank is the older style requiring a set screw to secure the blade. Unless you have a very old jigsaw, always choose T-Shank blades.

Burning is usually caused by: (1) Dull blade — replace it. (2) TPI too high for thick material — the fine teeth clog and generate friction heat. (3) Feed rate too slow — moving too slowly allows heat buildup. (4) Blade installed backwards — check tooth direction. Try a lower TPI blade and increase your feed rate slightly.

For tight curves, use a narrow, scroll-cut blade with a reduced blade width (often labeled "Curve" or "Scroll"). These blades have a narrower kerf and smaller blade body, allowing tighter turning radii. Typically medium to high TPI (10–18) works best. For very tight scrollwork, consider a spiral blade that cuts in all directions.

Aluminum is soft and tends to clog blade teeth. Use an HSS blade with lower TPI (8–12) — the larger gullets between teeth clear chips better. Apply cutting wax or lubricant, use a slower speed setting, and avoid forcing the cut. Bi-metal blades also work well for aluminum. Never use wood blades (HCS) on aluminum as they dull almost instantly.

Replace your blade when you notice: (1) Increased cutting effort or pushing force needed. (2) Burning smell or scorch marks on the workpiece. (3) Wandering cuts — the blade drifts off the cut line. (4) Visible chipped or missing teeth. (5) Excessive vibration. As a rule of thumb, a blade lasts 15–45 minutes of continuous cutting depending on material hardness.

Generally no. Wood blades (HCS) have larger, more aggressive teeth unsuitable for metal. Metal blades (HSS) have finer, harder teeth. However, Bi-Metal blades are a versatile compromise — they can handle occasional mixed-material jobs including wood, metal, and plastics. For dedicated metalwork, use HSS or Bi-Metal blades with appropriate TPI.

Tooth set refers to how teeth are bent outward from the blade body. Set teeth (alternating left-right) create a kerf wider than the blade, preventing binding and allowing chip clearance — common on wood blades. Wavy set (continuous wave pattern) is used for thin metal cutting. Ground teeth (not set, precision ground) provide the smoothest finish, used on metal-cutting blades.