Oscillating multi-tools (OMTs) have been getting a lot of attention lately — new brands, more advertising, and a growing presence at supply centers and big-box stores. There are two main reasons for this surge in interest: First, the tools are genuinely useful on the job site. And second, Fein's patent on the technology expired a few years ago.
As the originator, Fein made oscillating cutting tools for decades before marketing them to contractors. The very first model was a plaster cast-cutting tool for physicians that hit the market about 45 years ago. It evolved into an automotive body-cutting and windshield-removal tool, and then into a triangle sander. Not until the introduction of cutting and scraping blades did the device became the OMT we're familiar with today.
For this article I tested full-size OMTs — corded models and cordless ones with 14.4- or 18-volt batteries. I chose not to include 10.8-volt (12-volt maximum) tools, because their lack of runtime would make comparisons to larger models unfair.
How OMTs Work
The mechanism that gives these tools their oscillating action is quite simple. A bearing — slightly off-center with respect to the motor shaft — fits between a pair of arms that are connected to the blade-mounting spindle. With each turn of the motor, the bearing pushes the arms one way and then the other. It's a miniscule movement, but the high number of oscillations per minute (opm) allows the tool to work effectively. The opm matches the rpm of the motor, so at top speed the teeth on a cutting blade (which cut in both directions) could be taking 40,000 bites per minute.
The small angle of travel (between 2.8 and 4.0 degrees) accounts for the ease with which OMTs can be controlled as they cut, sand, and scrape. Because of the spindle's limited throw, the triangular sanding pad does not bounce out of corners. Scraping works in an unexpected way: The intense friction at the tip of the blade actually melts and softens old mastics and sealants — something you can't achieve with a putty knife.
Testing the Tools
To see what the tools could do, I spent several days using them for the kinds of tasks they'd be asked to perform on the job site. I cut baseboard in place over drywall, notched trim and framing, cut through drywall and floppy cabinet backs, and trimmed 1-by jamb material. When I wasn't cutting, I was sanding wood, removing grout, and scraping off old mastic. Click here to see my observations on the OMTs' performance.
I used Bosch blades for the comparative testing because their interface is the only one that fits or can be adapted to every tool tested. I did not set out to test accessories, but after using some from all of the makers who provided tools, it's my sense that the European-made Fein and Bosch/Makita blades are a cut above the rest. Their wood blades cut faster and truer without smoking, and their carbide-grit tools have a thicker and more even coating.
The traditional way to attach accessories is to bolt them to the spindle.
That's how it's done on the Ridgid, Makita, and Rockwell tools; the more-evolved machines have tool-free blade-mount systems. I prefer the tool-free approach because it makes it faster and easier to change or reposition blades.
Fein's blade clamp is controlled by a lever attached to the top of the housing; you pull up to release and push down to engage. A flanged holding pin comes free when the lever is released and clamps firmly over the accessory when the lever is engaged. The internal spring is very strong, so it takes a fair amount of force to retract the lever.
If you're not careful, the lever can "mousetrap" painfully onto your fingers when you push it back down. The spring is especially stiff on the corded SuperCut model.
Bosch's clamp lever is set into the side of the tool; it has smooth action and will not snap closed. The exposed positioning pins and spindle make it simple to attach and adjust accessories.
Porter-Cable's system is the easiest of all to operate. A spring-loaded lever clamps over the blade and positioning pins. Squeezing the lever frees the blade, and releasing the lever clamps the blade in place. The blades for the Porter-Cable tools are different from the others — they're open along the edge, so they can fit around (rather than over) the spindle.
The accessories for these tools represent six separate mounting types: Bosch/Makita, Fein MultiMaster, Fein SuperCut, Porter-Cable, Ridgid/Rockwell, and a new type of Ridgid mount that was introduced after I finished testing. Many OMTs include or can be equipped with adapters that allow them to use blades that don't match their mounts.
Adapters work best on tools with bolt-on accessories, because if there's any slop in the fit (as there sometimes is with adapters) you can make up for it by overtightening the bolt. You end up with a friction-fit, which is how accessories were attached in the days when the interface was a simple hole through the blade. Adapters will work with tool-less blade clamps, but there's no way to compensate for a questionable fit between tool and adapter or blade and adapter.
An OMT may be operated in multiple positions or for extended periods of time, so for the sake of comfort it's best to have smooth, contoured surfaces and rubber overmolding at the grip areas — including at the nose of the tool, which is frequently grasped during two-handed use.
Most of the tools have acceptably smooth surfaces for a variety of grips. The Bosch stands out for having the largest amount of useful rubber surfaces. The Porter-Cable tools are smooth enough, but the blade clamp lever gets in the way when you grip near the front.
Every OMT tested has variable speed. In most cases, there is an on/off switch near the center of the tool and a speed-control dial near the back. The location of the speed control hardly matters, though, because these tools are typically run at top speed. Ridgid's tool is the only model with a variable-speed trigger. This may have value for intermittent operation with some of the tool's other accessory heads, but the inability to lock the tool on is a negative when sanding or cutting for long periods of time.
The Ridgid and the cordless models from Makita and Porter-Cable have LED headlights that come on with the motor. They might provide usable light if you are cutting inside a cabinet. But if you're working on a reflective material like tile, they can produce glare that makes it hard to see.
Cases are important because they protect the OMT and keep your accessories with it. Most OMTs come with hard plastic cases; a few come with soft fabric bags. A bag takes up less space, but I prefer a case because it offers more protection and you can stow the tool without removing the blade. If you do that with a bag, the blade might chew through the bag or cord during transport.
Most of the kits come with a small plastic storage box for blades and accessories. The box stores in the tool bag or case. Porter-Cable's corded model does not require a box because there's a blade storage area built into the case. The Ridgid and corded MultiMaster kits have no blade storage — though there is room for a box in the MultiMaster's duffel. Ridgid's case is too small to store much more than the tool and a few loose accessories.
Corded or Cordless?
I was surprised by how powerful the cordless tools are in comparison to corded models from the same manufacturer. If it weren't for the batteries' added weight and limited runtime, it would have been hard to tell the two types of tools apart. Of the cordless tools tested, the SuperCut cut the fastest. The MultiMaster came in second, closely followed by the Makita. The Porter-Cable lagged far behind.
I tested runtime by putting 60-grit paper on the tools, lightly sanding particle board, and timing how long it took to deplete the batteries. The Makita sanded for 43 minutes, both Feins for 33 minutes, and the Porter-Cable for 26 minutes. By way of comparison, I performed the same test with a leading 12-volt Max OMT, and it sanded for only eight minutes.
Despite the strong performance of most of these tools, I doubt many tradesmen would gain much by going cordless. Rechargeable batteries work best when they get regular workouts, and few would get that when paired with an OMT. If the tool sits for a period of time, the batteries may be low when you go to use it. This would be less of a problem for people who buy a cordless OMT that takes the same batteries as their other cordless tools. They'd be using the batteries often enough to always have charged ones on hand.
OMTs vary widely in price, so before you buy, it pays to think about how often you'll really use the tool. The tradesmen I know who have an OMT say that they're glad to have it in the truck for those jobs that no other tool will do, but that they might use it only a dozen times per year.
When buying an OMT you should factor in the cost of consumables. Purchased separately, an assortment of five or six quality blades will set you back more than $100. Look for a kit that includes a decent variety of the blades and attachments you want to use. Don't be fooled by the numbers — I've seen 100-piece kits where 80 of those pieces were sandpaper.
If I were in the market for a corded OMT, I would buy the Bosch or the Fein MultiMaster; they're powerful and have quick tool-free blade-changing. The MultiMaster offers the advantage of being able to fit a variety of accessory brands, and the Bosch has a blade clamp that always locks tight the first time and won't snap shut on your fingers. Take your pick.
The Fein SuperCut is a top-quality tool with power to spare. It would be at the top of my list if I did the kind of work (removing sealants from exterior concrete wall panels or commercial glazing) where I used the tool hard every day. But it's too expensive for intermittent use and doesn't do anything that can't be done with the MultiMaster or Bosch.
Both the Makita and the Rockwell are solid second-tier tools that did everything asked of them — but the Makita did it better. The Porter-Cable and Ridgid tools felt like a compromise and trailed behind the other models.
Given how infrequently most tradespeople use OMTs, I would not recommend buying a cordless model unless you're already on the Makita battery platform — in which case you could get Makita's tool and be assured of having charged batteries around.
Michael Springer is the former executive editor of Tools of the Trade.