A few years back, I was watching my carpenter friend fix the trim around a door. A section of it was rotten, and I imagined he would replace the entire piece, but instead he pulled out an amazing tool, made a plunge cut straight into the trim, and removed only the rotten section. The tool was an oscillating multi-tool, and I quickly started thinking of the potential uses for boatbuilding and repair.

The multi-tool has a side-to-side rotating blade that swings just 1.6 to 5 degrees at up to 23,000 oscillations per minute. Its speed can be controlled for different materials: slower for metals and faster for wood.

The DeWalt multi-tool has a quick-release device for a tool-less change of blades and a variable speed trigger switch.Kent Lewis

The DeWalt multi-tool has aa variable speed trigger switch and a quick-release device for a rapid, tool-free change of blades.

Blades for multi-tools tools come in different shapes and materials for use with metal, fiberglass, or wood. We found a semicircular blade handy for reefing out caulked or glued seams and also for scribing and trimming a bevel along plank edges. The plunge-cut of oscillating saw blades allow us to precisely remove areas of rot and neatly trim the surrounding wood for dutchman repairs.

The blades are small, have a small range of motion, and can be attached at different angles, so the tool can reach into tight spaces or around corners. For long, straight cuts a blade guide is a useful attachment; it can also be used as a depth stop .

We’ve used the oscillating multi-tool to put scarfs into planks, doing those repairs while the planks were still attached to the boat. With a blade designed to cut through wood and nails we can cut through fastenings in the laps between planks.
If you’ve enjoyed using Japanese handsaws, there are multi-tool blades with teeth cut in the same way; they’re well suited for working with hardwoods.

Oscillating multi-tools do more than cutting. Triangular sanding pads can do sanding in small spaces that other sanding tools can’t reach, even all the way into corners; scraper blades speed up paint and excess epoxy removal.

The built-in light comes in handy for working in tight, poorly lit spaces.Kent Lewis

The built-in light comes in handy for working in tight, poorly lit spaces.

When we went shopping for a multi-tool we did our research and settled on DeWalt’s DWE315. It has a system that allows fast blade changes, without having to use a tool. We switch blades frequently when we work on seams and planks, and having to use a tool to change blades slows the work down and risks losing the fastening screw and washer. The DeWalt comes with a universal adapter, meaning we can use the full array of blades available, no matter which of the half-dozen fitting attachment configurations  might have. We like the long 10′ cord and the LED work light on the tool. The DeWalt has a variable-speed control trigger—rather than a switch as on some other models—and continuous-on trigger lock. The powerful 3-amp motor has been up to all the jobs we’ve done with the tool.

The teeth of wood-cutting blades can get dulled quickly by some materials; a dull blade will cut slowly and may even begin to smoke. Ridge Carbide makes a blade sharpener that is a stack of fifteen 3″ metal-cutting discs, separated by 1/16″ rubber washers on a 3/8″ arbor. We put one on our electric drill to sharpen burned-up blades in minutes, saving the time and money that comes with a trip to buy new blades. With sharp teeth, the work is easier and goes much quicker.

Bosch, Dremel, Fein, Hitachi, Porter Cable, and Rockwell all manufacture oscillating multi-tools. You may find one of them that is a worthwhile addition in your shop.

Kent Lewis and his wife Audrey maintain a fleet of small boats in Northwest Florida. Current boat works projects include restoration of a wooden Sunfish and new build of a diamond-bottomed catboat. Their adventure blog is www.smallboatrestoration.blogspot.com.

The DeWalt DWE315 is available from several stores and online vendors. It comes as a kit with blades, accessories, and case for prices as low as $119.

Editor’s note:

I bought Dremel’s Multi-Max 6300 (superseded by the Multi-Max MM30) to diminish the misery of sanding the interior of my bright-finished lapstrake Whitehall. With its narrow strakes and closely spaced steam-bent frames, there were hundreds of index-card-sized patches of planking to sand, and I didn’t want to subject my fingertips and knuckles to that kind of torture. The Ryobi Detail Sander 1000 I’d bought a few years earlier turned out to be a disappointment; it rattled in my hand so badly that it was painful to use and all that wasted motion made for inefficient sanding.

My Dremel Multi-Max has proven useful for jobs around the house and with my little fleet of boats. With the sanding attachment I use both ready-made sandpaper patches and homemade ones I cut from sanding disks. The two blades at right are universal blades with holes to fit most models of multi-tools.Christopher Cunningham

My Dremel Multi-Max has proven useful for jobs around the house and with my little fleet of boats. With the sanding attachment, I use both ready-made sandpaper patches and homemade ones I cut from sanding discs. The two blades at right are universal blades with holes to fit most models of multi-tools.

With the Dremel I feel a slight bit of buzz in the tool, and the motion is almost entirely directed to whatever accessory is attached to it. It doesn’t have all of the features that the DeWalt 315 does. There is no light, no variable-speed trigger, and no quick-release system for the blades; it has an on-off switch and a dial for varying the speed. The attachments are secured with a bolt and washer. (I lost the washer and had to trim a bolt washer to replace it.) But the DeWalt tops out at 22,000 oscillations per minute through an arc of 1.6 degrees, while the Dremel peaks at 23,000 opm through 3.2 degrees, giving it faster sawing capabilities. The Dremel’s wider angle also makes for more aggressive sanding; the DeWalt may do finer work.

The Dremel’s triangular sanding pad came in quite handy for sanding the Whitehall. It has a hook-and-loop attachment for sandpaper (the Ryobi used adhesive sandpaper—a nuisance in my book) and I don’t often buy the expensive made-to-fit sandpaper, I just cut out triangles from the 5” discs that I buy in bulk for random-orbit sanders. With a bit of Velcro, a worn-out saw blade also makes a good sanding tool. 

To get around having to stock and pay for the sandpaper pads for the sanding-pad attachment, I covered a multi-tool saw blade, bottom and top, with self adhesive hook-and-loop fastening tape (hook side). For sandpaper I cut rectangles from sanding disks, often times disks that I've already used on a random-orbit sander. The perimeters may be worn, but the centers are usually still useful.Christopher Cunningham

To get around having to stock and pay for the sandpaper pads for the Dremel’s sanding attachment, I covered a worn-out oscillating saw blade, bottom and top, with the hook part of self-adhesive, hook-and-loop fastening tape. For sandpaper, I cut rectangles from sanding disks, often disks that I’ve already used on a random-orbit sander. Their perimeters may be worn, but the centers still have some working life left in them.

The day before I wrote this, I installed a new kitchen counter and sink. The side panels of the cabinet underneath the sink prevented me from seeing, let alone reaching, the channels on the bottom of the sink’s flange that hold the clips that would secure the sink in place. With the Dremel I made plunge cuts in the tight space I had to work in and quickly removed the sections of 3/8” plywood that were in the way. No other hand tool or power tool could have done the job so easily. In earlier remodeling projects, I used the Dremel to trim the bottom ends of door trim prior to installing laminate flooring. While neither of these projects involved boats, they demonstrated the ability of an oscillating multi-tool to do quick work in cramped spaces and at inconvenient angles.

Is there a product that might be useful for boatbuilding, cruising or shore-side camping that you’d like us to review? Please email your suggestions.