How do I use a coping saw to cut a curve or scribe a joint?

The coping saw does two jobs nothing else does well: it cuts a tight curve in thin material, and it produces a scribed joint. A scribed internal corner is why professional skirting and coving joints stay closed when the house moves and a mitred one opens. Both jobs depend on the same small setup details.

What you'll need

• Coping saw
• Spare blades
• Clamp, vice or bench hook
• Pencil
• Half-round file or rasp (optional)

Step by step

1. Fit the blade teeth-first towards the handle.A coping saw is easiest to control cutting on the pull stroke, because the thin blade is in tension. Slacken the handle, hook the blade into both pins with the teeth pointing back at you, then tighten the handle to tension it.
2. Tension it properly.A slack blade wanders and snaps. Screw the handle down until the blade pings rather than buzzes when you flick it. Slacken it off again when you put the saw away, so the frame does not take a permanent set.
3. Rotate the blade to suit the cut.Both end pins turn, so the blade can be set at any angle to the frame. Set it so the frame clears the workpiece — this is what lets a small frame cut well inside a wide board.
4. Clamp the work so it cannot vibrate.Thin material chattering against the blade is the main cause of broken blades and ragged edges. Hold it low in a vice, close to where you are cutting, or against a bench hook.
5. Cut just outside the line, in the waste.Take the line off afterwards with a file or sandpaper. Trying to saw exactly to a curved line usually ends up inside it, and you cannot put material back.
6. Keep the blade moving as you turn.Turn the cut gradually while the blade is stroking. Twisting a stationary blade in the kerf is how blades break. For a very tight radius, cut a series of straight relief cuts into the waste first so the waste falls away in pieces.
7. To scribe an internal moulding, cut the first piece square into the corner.The piece in the corner runs full length, butted straight against the wall. Only the second piece is scribed to fit over its profile.
8. Mark the profile on the second piece and cut it at a back angle.Cut a 45 degree internal mitre on the second piece first — the mitre exposes the exact profile line as a crisp edge to follow. Then cope along that line with the coping saw, angled back at roughly 5 degrees behind the face, so the front edge is the only part that touches. The joint closes tight even when the corner is not 90 degrees.
9. Test, then file to fit.Offer it up, mark where it holds off, and take material from the back with a file. A scribe is fitted, not measured.

Tips

• For internal cut-outs, drill a hole in the waste, release one end of the blade, thread it through, and re-tension. That is the coping saw's other trick.
• Blades are cheap and blunt quickly. A blade that has stopped cutting is the reason most people think a coping saw is hard work.
• A fret saw is the same idea with a deeper frame and finer blades, for thin sheet and marquetry — not for skirting board.

Common mistakes

• Fitting the blade teeth-forward and pushing — The thin blade buckles in compression, wanders off the line and snaps. Pull-stroke cutting is far easier to control.
• Scribing without a back angle — Without relief behind the face, the back of the cut hits first and holds the joint open at exactly the point people can see.
• Mitring both pieces of an internal corner — Internal corners in houses are almost never 90 degrees, and a mitred internal joint opens as soon as the timber moves. A scribe absorbs both problems.

Questions people ask