This article appeared in the Fall 2023 issue of This Old House Magazine. Click here to learn how to subscribe.
After starting out as a tool for sawing off plaster casts without cutting skin, the oscillating multi-tool has become the Swiss Army knife of power tools. The key is its cutting action. Unlike a typical saw blade, the cutter on an oscillating multi-tool wiggles from side to side —by just a few degrees — at speeds up to 20,000 oscillations per minute. Many pros use these tools exclusively for plunge and flush cuts: when trimming door jambs to fit new flooring or cutting receptacle recesses in drywall, for example.
But DIYers have also discovered that oscillating multi-tools can be just as indispensable as detail sanders, metal cutters, caulk removers, grout grinders, and more. Here’s how to choose and use this toolbox essential to maximize its versatility.
Oscillating Multi-Tools: Features and Upgrades
Here’s what to look for when selecting your multi-tool:
- Mounting plate: The spot where accessories attach
- Tool-free blade change: A lever that locks accessories to the plate
- Oscillating angle: The larger the angle, the more aggressive the tool; most often a fixed side-to-side motion between 2° and 5°
- Work light
- Grippy rubber handholds: Enables using the tool at multiple angles
- Speed control: A dial or switch (on this tool’s other side) that sets the number of oscillations per minute
- Dust extractor: A attachment that connects to a shop vac to remove debris
- Accessory kit: Ensures the tool’s ready for a range of tasks
- Case: Keeps the tool and its accessories in one spot
4 Ways to Use a Oscillating Multi-Tool
An oscillating multi-tool earns its keep in myriad ways. Here’s how to put this multitasker to use—and get the best results.
After selecting the blade that matches the work, start at a slower speed to establish a kerf, then increase the speed while rocking the blade to use more teeth and lifting it up and down to eject sawdust. With vertical cuts, work from the bottom up so that the sawdust has a place to go.
Set a piece of laminate or flashing under the blade, plunge the scraper into the caulk or putty, and then work the blade left and right, “cutting” with the side of the blade as much as the tip. Set the tool on medium with a larger blade, but slow down for more control with narrower blades and in tight spaces.
A grit-encrusted blade is ideal for removing grout or hardened thinset that’s oozed up between tiles. Start by scoring a light line to guide the tool. Focus on keeping the tool perpendicular to the surface to avoid chipping nearby tiles. Rotate the blade while working to maximize its working life.
The secret to removing finishes faster is to watch your speed; full-speed sanding can cause finishes to melt and clog the pads. Keep in mind that the tool’s oscillating action leaves more scratches than random-orbit sanding, so it’s important to work through sanding-pad grits from coarse to fine.
Tips for Making Cuts with Oscillating Multi-Tools
A multi-tool may be one of the safest and most straight-forward cutting tools in the workshop, but there are tricks that can help you achieve cleaner cuts and maximize blade life.
- PLAY THE ANGLES: Multi-tools don’t need to cut straight ahead. Don’t be shy about rotating a blade or holding the tool in whatever way optimizes control and visibility.
- WATCH YOUR SPEED: Heat ruins accessories almost as quickly as hidden hardware. If the workpiece starts smoking, ease up on the trigger and pressure, and lift the tool to clear sawdust clogging the teeth.
- USE GUIDE BLOCKS: To ensure surgically straight cuts in flooring or drywall, attach a strip of wood to the good side of the cut. Set the blade against the guide, turn the tool on, and then gradually plunge the blade into the work.
- TRACK YOUR DEPTH: Wrapping a piece of painter’s tape around the blade to mark the depth of cuts on drywall makes it easy to see how deep you’ve cut while you’re working.
- KNOW THE TOOL’S LIMITS: Multi-tools are best suited to detail work and for finishing what bigger tools have started. Starting cuts with a circular or reciprocating saw will save time, and you’ll spend less money on multi-tool blades.
Mastering essential cuts
Precise plunge cutting
When making a plunge cut in drywall, plywood, or flooring, start at a slow speed, sink in a corner of the blade, and then pivot the tool so that the blade rests on your cutline. Gradually work the blade along the line.
Making space for flooring
When installing new flooring, it’s more accurate to cut the door jambs and casing using a piece of the scrap. Place the blade flat on the scrap, then start cutting from the thinnest section of molding to the thicker end.
Essential Multi-Tool Attachments
From blades to sanding pads, most multi-tools come with a few attachments to get you started, but to maximize the multi-tool’s utility, get to know the array of available options.