Jigsaw

A jigsaw holds a short, narrow blade in a chuck and drives it up and down through a flat shoe that rides on the work. Nothing else in a small shop cuts a curve as cheaply, and nothing else can start a cut in the middle of a panel — drill a hole, drop the blade in, and go. What it gives back in exchange is edge quality: a jigsaw's cut is rougher and less square than a band saw's, and it is meant to be, because the blade is only held at one end.

That one fact explains most of the tool. A band saw blade runs in a loop through guides above and below the cut, so it stays where it's put. A jigsaw blade is a cantilever, gripped at the top and free at the bottom, and it will flex — away from a tight curve, off a line in thick stock, and out of square through the whole cut. Cutting to a line and sanding or routing to the line afterwards is the normal way to work, not an admission of failure.

The blade is most of the decision

Blades are cheap, specific and swapped often. Three things matter:

• Shank. T-shank is the modern standard and fits nearly every saw made in the last twenty years; U-shank is the older style. Buy T-shank unless the saw says otherwise.
• Teeth per inch. See TPI: coarse blades (6-10 TPI) cut wood fast and roughly, fine blades (10-20 TPI) cut slower and cleaner, and metal-cutting blades run finer still. A blade should have at least three teeth in the material at all times.
• Tooth direction. Standard blades cut on the upstroke, which throws tearout onto the face that's pointing at you. Down-cut blades reverse that, leaving the top face clean at the cost of a slower, grabbier feed. Cutting good-face-down with a standard blade is the free version of the same fix.

Blade width matters for curves the way it does on a band saw: a narrow blade turns tighter, a wide one tracks straighter. A blade too wide for the radius you're asking of it will bind and flex rather than turn.

Orbital action

Most jigsaws swing the blade slightly forward on the cutting stroke, in three or four settings plus off. More orbit means a faster, rougher cut; off means slow and tidy. The setting that belongs on a rough cut through 18mm plywood is the wrong one for a finish curve in hardwood or for anything in metal or plastic, where it just chews. Turn it off when the cut has to look good and when following a tight radius.

Where it wins, and where it doesn't

Its real advantages are portability, curves, and interior cuts — a sink cutout in a fitted worktop, a hole for a fan in a cabinet back, a handle slot in a carcase side. Its real limits are straight lines and square edges. For a straight cut in sheet goods, a circular saw against a straightedge is faster and cleaner; for repeatable curves in thick stock, a band saw is the machine. For tight interior fretwork, a coping saw still goes places no power tool reaches.

The squareness problem is worth knowing before it surprises you: in stock thicker than about 25mm, a blade under side load can leave a cut that's a degree or two out on the underside even though the shoe stayed flat. Let the saw set its own feed rate — pushing harder is what bends the blade.

Safety

The blade keeps moving after the trigger is released, so let it stop before setting the saw down or lifting it away; a coasting blade against a leg or a benchtop is the everyday injury here. Keep the shoe flat on the work throughout the cut — tipping it is what snaps blades and what lets a saw kick sideways off the line. Support the offcut so it can't fold down and pinch the blade, and clamp small work rather than holding it. Eye protection matters more than it looks like it should: jigsaws fling chips upward, straight at your face.