How to cut a perfect circle on a scroll saw with a compass jig

A scroll saw can produce remarkably clean circles, but freehand cutting usually leaves small waves, flat spots or an uneven kerf. A simple compass jig removes most of that guesswork. It holds the workpiece at a fixed radius while the timber rotates steadily around a centre pin.

The method suits clock faces, round plaques, inlay blanks, toy parts, decorative panels and other small woodworking projects. It works with plywood, MDF and many solid timbers, although dense Australian hardwoods may need a slower feed and a sharper blade.

The essential measurement is the distance between the scroll saw blade and the pivot pin. Set that distance to the finished radius, secure the workpiece on the pin and rotate it gradually into the blade. The jig does the guiding, while the operator controls the pace.

Australian makers can use the same approach in millimetres, which is convenient when working with 6 mm, 9 mm, 12 mm or 18 mm sheet goods from a local hardware supplier. Sloan’s Woodshop provides scroll saw blades, plywood, sanding supplies and related accessories, with orders handled by toll-free phone and shipping available within the United States.

Choose the timber and blade

Start with a flat, stable blank that is larger than the finished circle. A square or rectangular piece is easier to position on a jig than a pre-cut rough circle. Check both faces for cupping, loose knots or damage that could make the timber shift as it turns.

Plywood is often the easiest material for a first attempt because its layers remain relatively stable. Baltic birch-style plywood gives a clean edge and is well suited to clock faces and painted projects. MDF cuts smoothly but creates fine dust, so use effective extraction and avoid allowing dust to build around the saw table.

Blade selection depends on thickness, grain and the finish you want. A fine-tooth blade gives a smoother edge in thin plywood, while a slightly coarser blade clears waste more effectively in thicker stock. If the blade wanders, burns the timber or requires force, replace it rather than trying to compensate with the jig.

For Australian native timbers such as spotted gum or Tasmanian oak, test the blade on an offcut first. These materials can behave differently from softwood and imported plywood. A sharp skip-tooth or precision-ground blade may help with thicker pieces, but the correct tension and a steady feed matter just as much.

Build the compass jig

A basic compass jig can be made from a straight, rigid strip of plywood, MDF or hardwood. It should be long enough to reach from the front of the scroll saw table to the blade, with room for the largest circle you expect to cut. The strip must sit flat and must not flex as the workpiece rotates.

Drill a small hole for a pivot pin near one end. A smooth nail, machine screw or short dowel can serve as the pin, provided it fits the hole in the workpiece without excessive wobble. The pivot should stand square to the jig and be firmly fixed from below.

Position the jig so its edge or centreline runs towards the blade. The blade should pass through a small opening or slot in the jig without rubbing against it. Clamp the jig to the scroll saw table, then measure from the blade’s cutting line to the centre of the pivot pin.

That measurement is the radius, not the diameter. For a 200 mm finished circle, set the blade-to-pin distance to 100 mm. Mark several common settings on the jig if you make round parts regularly. For another approach to circle cutting, this band saw circle jig explains the same radius-and-pivot principle on a larger machine.

Mark the centre accurately

Find the centre of the blank before placing it on the jig. On a square piece, draw two diagonal lines from opposite corners. Their intersection is the centre. On an irregular blank, use a ruler, compass or centre-finding template rather than estimating by eye.

Mark the centre on the face that will sit against the jig. Drill a pilot hole that matches the pivot pin. The hole should be deep enough to hold the workpiece securely, but it need not pass through the finished circle. If a visible hole would spoil the project, plan for it to fall inside the waste area or fill it later.

Some makers drill a small hole through the centre and use a temporary dowel. This is useful when the centre will later receive a clock insert, medallion or other fitting. If you are making a clock face, check the insert dimensions before cutting; the difference between a friction-fit opening and a glued opening is covered in this clock insert guide.

Place the blank on the pivot and turn it by hand. It should rotate freely without lifting from the jig. If it rocks, enlarge the pivot hole only slightly or use a washer and a low-profile screw head to keep the workpiece seated.

Set up the scroll saw safely

Fit the blade with the teeth pointing down towards the table, then set the tension according to the saw manufacturer’s instructions. A correctly tensioned blade should feel firm and should produce a clear note when lightly plucked, though the manual remains the best guide for a particular model.

Lower the blade guard or hold-down foot until it sits just above the workpiece. It should prevent lifting without restricting rotation. Confirm that the blade is square to the table from the front and side. A blade that leans will produce a bevelled circle even if the jig is perfectly set.

Before switching on, rotate the blank through a complete revolution by hand. Look for clamps, the pivot head, the jig edge and any part of the blank that could contact the saw arm. This dry run is especially important with a large workpiece or a benchtop saw in a compact Australian garage or shed.

Wear eye protection, keep fingers away from the blade path and use dust extraction where possible. Do not force the timber. If the blade begins to bind, switch off the saw and wait for it to stop before investigating.

Cut the circle steadily

Turn on the saw and let the blade reach full speed. Rotate the workpiece slowly into the blade, keeping the pivot engaged. The cut should begin smoothly rather than with a sudden push. Maintain light, even pressure so the teeth remove material without bending the blade.

Keep both hands on the workpiece at safe positions well away from the blade. One hand can guide the rotation while the other keeps the blank flat against the jig. Do not twist the workpiece sideways, because lateral pressure can deflect the blade and create a tapered or lumpy edge.

For thick stock, pause occasionally to clear dust and check that the blade is not overheating. A circle cut is continuous, so the blade spends a long time in the timber. Slowing the feed is usually better than increasing pressure. If the cut feels tight, back out carefully with the saw running rather than forcing the workpiece forward.

The final section of the cut may release suddenly. Keep the blank supported and continue rotating until the circle is completely free. Stop the machine before removing the workpiece or clearing the offcut.

Refine the edge and correct errors

Remove light fuzz with fine abrasive wrapped around a small sanding block. Sand with the block held square to the edge rather than rounding the perimeter by hand. A spindle sander can speed up the process, but it is easy to remove too much material, so use a light touch.

If the circle is slightly undersized, the cause is often an incorrectly measured radius, blade deflection or a pivot hole that was not centred. Measure the finished diameter at several points. If the readings differ, inspect the blade tension and the jig for movement before changing the setting.

A small flat spot usually means the workpiece stopped rotating briefly. A wavy edge can result from pushing too quickly or using a blade that is too fine for the timber. Make a test cut in scrap and adjust one factor at a time.

When the edge will be painted, minor marks can be filled with compatible timber filler. For a clear finish, accurate cutting and careful sanding are more important because glue lines, scratches and end-grain variation remain visible. Seal both faces and the edge of plywood to reduce moisture movement, particularly in humid coastal areas such as Brisbane, Sydney or Darwin.

Match the jig to the project

The jig is most useful when its dimensions match the work. A small compass strip is convenient for clock faces and ornaments, while a longer, wider base gives better support for large plaques. Keep the pivot hardware low enough that it cannot catch on the saw arm or guard.

For a project inspired by coastal craft, a circle jig can produce curved components for a timber surfboard display, wall art or a round mounting panel. Before cutting an expensive sheet, practise on scrap and confirm the grain direction, finish allowance and hardware placement. These surfboard woodworking plans can provide useful ideas for related curved timber work, even when the final piece is made with a scroll saw.

Metric layout is straightforward: divide the desired diameter by two, then set the blade-to-pin distance to that number. If a plan uses inches, convert carefully rather than relying on a rough visual estimate. A difference of only 2 or 3 mm can matter when fitting a clock insert or joining a circle to another component.

Finished diameter	Pivot radius	Suitable starting material	Useful application
100 mm	50 mm	6 mm plywood	Small ornament or coaster
200 mm	100 mm	9–12 mm plywood	Clock face or plaque
300 mm	150 mm	12–18 mm plywood	Wall art or sign
400 mm	200 mm	18 mm plywood or solid timber	Large decorative panel

Make repeatable cuts with these habits

Once the compass jig is calibrated, record the blade type, timber thickness and radius that produced the best result. A pencil scale on the jig is helpful, but verify the setting with a ruler each time. Timber dust, blade changes and small shifts in the jig can affect accuracy.

For repeat work, use the same pivot-hole size and mark the centre with a template. Keep spare blades available, especially when cutting dense timber or a batch of plywood circles. A clean, sharp blade produces less heat and leaves less sanding for later.

A few practical habits make the process safer and more consistent:

• Clamp the jig securely and check it again after the first test cut.
• Measure from the actual blade teeth, not from the saw arm or blade clamp.
• Keep the workpiece flat while rotating it around the pivot.
• Test the radius on scrap before cutting finished material.
• Leave a small finishing allowance when an insert or inlay must fit precisely.
• Sand the edge with a flat block and inspect it before applying finish.

With a rigid jig, an accurately marked centre and a patient feed rate, a scroll saw can cut circles that are clean, repeatable and ready for finishing. The technique is simple enough for a home workshop in Adelaide, Perth or regional New South Wales, yet precise enough for detailed craft projects and fitted components.