Jigsaw and Finishing Sander: Clean Curves, Neat Cut-Outs and a Smooth Finish

A fundi in a roadside furniture shop is fitting a kitchen worktop. The sink needs a neat oval cut-out in the middle of a blockboard sheet, the cabinet doors need a curved top rail, and the client wants the whole job varnished by Friday. A panel saw cannot start a cut in the middle of a board, a circular saw cannot turn a curve, and hand sanding a full kitchen of doors takes days. Two modest power tools solve all three problems: a jigsaw and a finishing sander.

These are the tools that turn rough joinery into furniture people pay good money for. They are also two of the most misused tools in any workshop. A jigsaw run with the wrong blade wanders off the line and splinters the face of an expensive board. A sander pressed too hard leaves swirl marks that only show up once the varnish goes on, which is the worst possible moment to find them.

This guide explains how each tool works, how to choose blades and sandpaper grits, the settings that matter, the techniques for clean curves and cut-outs, and how to deal with the fine dust both tools produce. It finishes with what the tools cost at Fuga.

What a Jigsaw Does Well, and What It Does Not

A jigsaw drives a short, narrow blade up and down through the work. Because the blade is narrow and only held at one end, it can turn tight curves and start cuts in the middle of a panel from a drilled hole. That makes it the tool for sink and hob cut-outs, curved shelf brackets, shaped signboards, arched door heads, holes for pipes in cabinet backs and any outline drawn freehand on a sheet.

The same narrow blade is its weakness. A long, straight rip along an 8 foot sheet of plywood is slow with a jigsaw, and the blade tends to flex and drift, so the edge is rarely perfectly square. For long straight cuts a circular saw with a guide is faster and truer; our comparison of the circular saw and mitre saw covers those machines. The jigsaw earns its place on everything else.

Most jigsaws in Kenyan workshops have four controls worth understanding:

• Speed. A variable trigger or dial sets strokes per minute. High speed suits wood; lower speed suits metal, plastics and laminates, which overheat or melt at high speed.
• Pendulum (orbital) action. A lever that makes the blade swing forward on the cutting stroke as well as moving up and down. More orbit cuts softwood faster but rougher. Zero orbit gives the cleanest cut and is the setting for metal, tight curves and finished faces.
• Bevel shoe. The base plate tilts, usually up to 45 degrees, for angled cuts. Check it is locked back at zero before ordinary work, because a shoe that has slipped a few degrees gives an edge that looks square but is not.
• Blade clamp. Most modern machines take T-shank blades in a tool-free clamp. Older machines may take U-shank blades. Check which your machine uses before buying blades.

Choosing the Right Jigsaw Blade

Blade choice decides the quality of the cut more than the machine does. The key number is TPI, teeth per inch. Fewer, larger teeth remove wood fast but leave a rough, torn edge. More, smaller teeth cut slower but cleaner. Metal needs many fine teeth, because a coarse tooth catches on thin steel and snatches.

A practical rule of thumb used across the trade is to keep at least three teeth in the material at any moment. On thin sheet that means a fine blade; on thick timber a coarser blade clears the sawdust better and does not overheat.

Blade material matters too. Plain high carbon steel blades are cheap and fine for softwood. High speed steel or bi-metal blades are needed for metal, and bi-metal blades also last far longer in hardwood and blockboard, where glue lines blunt teeth quickly. Down-cut or reverse-tooth blades cut on the downstroke and leave a cleaner top face, which helps on laminated and melamine boards.

Technique: Straight Lines, Curves and Cut-Outs

Most bad jigsaw cuts come from forcing the tool. The blade needs time to clear its sawdust. Push too hard and it bends sideways, so the top of the cut follows the line while the bottom drifts off, leaving an edge that is out of square.

1. Clamp the work and support both sides. The jigsaw vibrates; work that moves gives a wavy cut. Support the offcut too, so it does not drop, tear the last of the cut or pinch the blade.
2. Check underneath. The blade sticks out below the board. Make sure the path is clear of the bench top, clamps, cables and your own hand.
3. Start at full speed before touching the wood. Rest the front of the shoe flat on the work, start the motor, then feed into the line. Keep the shoe pressed flat all the way.
4. Steer gently on curves. Turn the tool slowly and let the blade follow. For tight curves, make relief cuts first: straight cuts from the edge in to the line, so waste pieces fall away as you go and the blade never has to twist.
5. Let the blade stop before lifting it out. Lifting a moving blade out of the cut is how blades catch the edge, snap or chip the face.

For a cut-out in the middle of a panel, such as a sink in a worktop, drill a starter hole inside the waste area first, big enough for the blade to drop through. A 35 mm Forstner bit gives a clean round hole that doubles as the curved corner of a rectangular cut-out, so the corners come out neat instead of jagged. Our drill bits guide explains which bits suit which material. Plunge cutting by tilting the running blade into the board is possible, but it is a skill for experienced hands and it is hard on blades; a drilled hole is safer and neater.

For a straight line that must be truly straight, clamp a batten or a steel rule to the board as a fence and run the edge of the shoe along it. Measure the distance from the blade to the shoe edge once and write it on the tool; our guide to measuring and layout tools covers marking out accurately in the first place.

The Finishing Sander: How It Works and Why Grit Order Matters

A finishing sander, also called an orbital or sheet sander, holds a rectangle of sandpaper on a flat pad that moves in small, fast orbits. It removes little material at a time, which is the point. It is a finishing tool, made to take a surface that is already flat and make it smooth and even before paint, varnish or polish. It is not the tool for taking a board down several millimetres or flattening a twisted top; that is the work of a planer, covered in our wood planer and router guide.

Sandpaper is graded by grit number. A low number means coarse grit that cuts fast and leaves deep scratches. A high number means fine grit that cuts slowly and leaves fine scratches. Each grit's job is to remove the scratches left by the grit before it, so the order matters more than the final grit.

Jumping straight from 80 to 180 is the classic shortcut. The 180 grit polishes the tops of the deep 80 grit scratches and the surface feels smooth to the hand, but the scratches are still there. Varnish and stain soak into them and turn them into dark lines across the work. Going through each grade costs minutes; sanding back a varnished door costs hours.

Sanding Technique That Avoids Swirl Marks

• Let the weight of the tool do the work. Pressing hard slows the orbit, heats the paper, clogs it and leaves swirls. Light hand pressure is enough.
• Keep the pad flat and moving. Tilting the sander to attack a spot digs a hollow. Move slowly and steadily across the whole surface in overlapping passes.
• Start and stop on the work. Lifting a running sander on and off the edge rounds over the edges you meant to keep crisp.
• Change the paper when it stops cutting. Clogged, worn paper rubs and heats instead of cutting. Tap or blow out the dust between passes, and replace it rather than pushing harder.
• Finish with the grain. Even with an orbital action, a last pass along the grain, by hand with a sanding block if needed, hides the faint circular pattern.
• Raise the grain before water-based finishes. Wipe the sanded surface with a damp cloth, let it dry, and give it a last light sanding. Fibres that would have stood up under the first coat are cut off now instead.

Curved edges cut with the jigsaw are awkward for a flat pad. Shape and smooth them with a half round wood file or a round wood file first, then finish by hand with paper wrapped around a dowel or a curved block.

Dust, Noise and Electrical Safety

Both tools turn wood into fine dust, and the sander makes the finest. The International Agency for Research on Cancer classifies wood dust as a cause of cancer in humans, chiefly of the nose and sinuses in people exposed for years, and fine dust also irritates the lungs and can trigger asthma. A fundi sanding every day is exactly the person at risk, so dust control is not optional.

Use the sander's dust bag or port, and empty it often, because a full bag stops collecting. An aspirator blower set to suction is useful for cleaning the work and bench between grits. Use blowing mode only outdoors and away from people, since it simply moves the dust somewhere else. Wear safety glasses with the jigsaw, which throws chips upward, and ear protection for long sessions. Our guide to workshop safety and PPE covers masks, glasses and ear defenders in detail.

Unplug the jigsaw before changing a blade; a trigger knocked with a hand in the clamp area is a serious injury. Check cables for cuts before each job, keep the cable behind the tool and away from the blade path, and run both tools from a sound socket or a protected extension; our guide to extension cables and electrical safety explains how to size one. Fine wood dust can also build up inside motors, so blow out the vents of both tools regularly, outdoors, with the tool unplugged.

What the Tools Cost at Fuga

These items from our price list make up a small shaping and finishing kit. Prices can change, so confirm before buying, and ask in branch about blades and sandpaper to suit your work:

Getting Started This Week

If you are adding these tools to a workshop, start with a practice board. Cut a few curves with a coarse blade and a fine blade, with and without pendulum action, and look at both faces of each cut. Then sand one half of the board through every grade and the other half straight from 80 to 180, stain both, and look at the difference. Twenty minutes of testing teaches more than a year of guessing, and it is far cheaper on offcuts than on a client's worktop.

A jigsaw and a finishing sander are inexpensive, but together they lift the quality of everything a joinery shop makes. Ask at any Fuga branch or on WhatsApp 0716 961 018 about workshop tools for your furniture and joinery work.

Frequently Asked Questions