Keyhole Saw

What Is a Keyhole Saw?

A keyhole saw is a small, pointed hand saw designed for cutting openings and tight curves in thin or semi-rigid materials. Its blade is narrow and tapered to a sharp tip that can pierce materials like drywall, softwood, and plastic, allowing you to start cuts away from an edge. With a comfortable pistol-style handle and fine to medium teeth, it’s handy for making precise cutouts where larger power tools won’t fit or would create too much mess.

Common DIY Uses and Applications

Keyhole saws shine on tasks that require controlled, detailed cuts:

Cutting openings in drywall for electrical boxes, light switches, outlets, and recessed lights
Trimming drywall around door frames, windows, and HVAC registers
Notching cabinet backs or shelves to clear pipes, cords, or moldings
Shaping small curves in thin plywood, paneling, or laminate underlayment
Enlarging or fine-tuning holes made by a hole saw or oscillating tool
Cutting access holes in soffits, closet walls, or under-sink panels for maintenance

Because the blade is narrow, you can steer it around tight radii and follow drawn lines with good accuracy. For single or occasional cutouts—especially in finished spaces—many DIYers prefer a keyhole saw over setting up a jigsaw or creating dust with a rotary tool.

Types and Variations

Manufacturers use overlapping names, but these are the common variations:

Fixed-blade keyhole (compass) saw: A rigid, tapered blade permanently attached to a handle. Good for general drywall and wood work, with a solid feel.
Pad saw (replaceable blade): A handle with a slot that accepts interchangeable blades. Useful if you cut different materials and want to swap tooth patterns or replace dull blades quickly.
Retractable or folding blade: The blade slides or folds into the handle for safer storage and pocket carry. Handy on ladders or crowded tool belts.
Drywall jab saw: A beefier version designed to pierce gypsum board by “jabbing” the tip through the surface. Usually has coarse teeth (6–8 TPI) to move quickly through drywall.

Other features to consider:

Tooth count (TPI): Coarser (6–9 TPI) cuts faster in drywall; finer (10–14 TPI) leaves smoother edges in wood, PVC, and paneling.
Blade stiffness: Stiffer blades track straighter and are less likely to wander or buckle.
Tip design: Sharpened, chisel-like points pierce drywall with less force.
Coatings: Anti-rust or low-friction coatings reduce drag and help with cleanup.

How to Choose the Right Keyhole Saw

Match the tool to your typical tasks:

Primarily drywall work: Choose a jab-style or fixed keyhole saw with a sharpened tip, coarse teeth, and an ergonomic handle with a non-slip grip.
Mixed materials (wood, PVC, paneling): Go with a pad saw or retractable style with replaceable, finer-tooth blades (10–14 TPI).
Occasional carry on site: Retractable or folding models improve safety and protect the blade in your pouch.
Comfort and control: Test grip size and handle shape—fatigue and blisters reduce accuracy. A comfortable handle makes a big difference on long cuts.

Check that the blade tracks straight, feels rigid under moderate pressure, and that replacement blades are readily available if the design supports them.

How to Use a Keyhole Saw (Step by Step)

Plan and mark: Use a template for boxes or fixtures, or trace the item you’re fitting. Check layout for level and plumb.
Scan the area: Before cutting walls or ceilings, scan for studs, wires, and pipes with a stud finder and voltage detector. If in doubt, open a small inspection hole first.
Create a pilot start: For drywall, you can pierce with the saw tip. For wood or plastic, drill a 3/8–1/2 inch pilot hole at an inside corner to avoid splitting or cracking.
Start the cut: Insert the tip at a shallow angle and use short, controlled strokes. Keep your other hand clear of the blade path.
Follow the line: Saw just outside your layout line. You can trim back to the line once the piece is free. For curves, take small bites and pivot the handle rather than bending the blade.
Support the work: On ceilings or larger panels, support the cutout section to prevent tearing as you complete the cut.
Clean up the edges: Use a utility knife, rasp, or sandpaper to fine-tune the opening for a snug fit.

Safety and Maintenance Tips

Protect yourself: Wear safety glasses; add a dust mask for drywall. Gloves help with grip but keep fingertips away from the tip.
Mind what’s behind: Cut shallow until you’re sure there are no hidden utilities. Angle the blade to avoid plunging too deep.
Use smooth strokes: Let the teeth do the work—excess force can crack panels or cause the blade to wander.
Store safely: Use a sheath or retractable handle to cover the sharp tip. Don’t toss it bare into a tool bag.
Keep it clean: Wipe off drywall dust and pitch; a drop of light oil prevents rust. Replace heavily worn or kinked blades rather than trying to straighten them.

Common Mistakes to Avoid

Forcing the pierce: Slamming the tip through drywall can blow out the back paper and create ragged edges. Use a controlled jab and support the area if possible.
Skipping the pilot hole in wood/plastic: Piercing these materials with the tip can split or crack them. Drill first for a cleaner start.
Using the wrong tooth pattern: Coarse teeth in thin plastic can chatter and chip; fine teeth in thick drywall are slow and clog easily.
Bending the blade in tight curves: Over-twisting can permanently kink the blade. Make relief cuts or use multiple small passes.
Ignoring hidden hazards: Cutting into live wiring or pipes is dangerous and costly. Always scan and probe before committing to the full cut.

Related Terms and Tools

Jab saw/Drywall saw: Heavy-duty keyhole-style saw optimized for gypsum board.
Pad saw: Handle with replaceable narrow blades for various materials.
Compass saw: A larger, narrow-blade hand saw for curves in wood.
Coping saw: Frame saw for detailed curved cuts and trim work in wood.
Hole saw: Drill-mounted cup saw for round holes.
Oscillating multi-tool or jigsaw: Power-tool alternatives for faster cutouts or thicker materials.

Practical Examples

Outlet cutout in drywall: Trace the electrical box, scan for wires, pierce with the tip, and saw just outside the line. Test-fit the box and pare edges with a knife.
Notching a cabinet back for a pipe: Mark the pipe location, drill a pilot hole, and use a fine-tooth blade to cut a smooth, semi-circular notch without splintering.
Enlarging a vent opening: After removing the grille, mark the new size and use short strokes to expand the opening, supporting the cutout to avoid tearing.
Scribing a panel: For a tight fit against an irregular surface, cut small, controlled curves to follow the scribe line, minimizing gaps before fastening.