Which oscillating multi-tool blade do I need?

An oscillating multi-tool cuts by vibrating a blade through a very small arc at high frequency. It is slow by design and that is the price of its unique ability: it cuts flush to a surface, plunges into a wall or a floor without a run-up, and cannot kick back. Blade choice is what separates a tool that does a job in two minutes from one that seems to do nothing at all.

Step by step

1. Choose the shape by what the cut has to reach.A straight plunge-cut blade goes into a surface from anywhere — cutting a socket aperture, notching a floorboard, trimming a door architrave for flooring. A segment or half-moon blade has a longer curved cutting edge for straight flush cuts and clears its own waste better.
2. Choose HCS for clean timber and plastic.High carbon steel blades are the cheapest and cut fast in softwood, plywood, plastic and plasterboard. They blunt instantly on any metal, so they are for known-clean material only.
3. Choose bi-metal for anything that might contain a fixing.Hardened teeth welded to a springy backing. This is the blade for cutting through a nailed floorboard, trimming a door frame with unknown screws in it, or cutting a nail flush. Almost all reclaimed and fixed-in-place timber needs one.
4. Choose carbide for abrasive and hardened material.Carbide-toothed or carbide-grit blades handle cement board, hardened screws, fibreglass, and repeated cuts in nail-embedded timber. They cost several times what a bi-metal blade does and last many times longer in those materials.
5. Choose diamond for grout, tile and stone.A diamond-grit segment blade cuts grout out of a joint, trims tile edges and works on stone and cement. It has no teeth — it abrades. Use it dry only for short bursts and let it cool.
6. Add a scraper for adhesive and sealant.A rigid scraper blade removes old flooring adhesive, silicone, paint and vinyl. A flexible one is for gaskets and delicate surfaces. This is the accessory that most surprises people with how useful it is.
7. Add a rasp for shaping.Carbide-grit rasp attachments, triangular or flat, remove timber, filler, plaster and mortar in awkward corners where nothing else fits.
8. Check the fitting before you buy.Most modern tools use a universal star-shaped or OIS-compatible interface, and many take a quick-change lever. Older tools use a proprietary fit. Buying the wrong interface is the commonest wasted purchase with this tool.
9. Use it correctly so the blade lasts.Let the blade oscillate at speed and apply light, steady pressure — pushing hard just generates heat and blues the teeth. Move the blade slightly side to side in a long cut so the whole edge wears evenly rather than a single spot.

Tips

• Blades cost more than the tool over its life. Buying good bi-metal blades in a multipack works out far cheaper than a stream of cheap HCS ones that blunt in one cut.
• Mark a depth line on the blade with tape when cutting into a floor or a wall so you cannot go deeper than intended.
• For undercutting a door frame or architrave, lay a flooring offcut on the floor and rest the blade on it — it sets the height perfectly and stops the blade dropping.
• A blunt blade heats the workpiece and can scorch it. If a blade stops cutting and starts smoking, change it rather than pushing.

Common mistakes

• Using an HCS wood blade on a nailed floorboard — One nail takes every tooth off. Use bi-metal for anything fixed in place.
• Pushing hard to speed the cut up — The tool cuts by oscillation, not by pressure. Force produces heat, blues the teeth and slows the cut.
• Buying the cheapest multipack for everything — Cheap HCS blades are false economy on anything except clean softwood, which is a small fraction of what the tool actually gets used for.

Questions people ask