How to Drill a Square Hole

The QuadSaw can be chucked into a drill and used to cut perfectly square and rectangular holes in drywall. The attachment is the brainchild of

T. Michael Sebhatu, an African refugee turned engineer, who saw a tradesman installing electrical boxes and decided there had to be a faster, more accurate way than marking and cutting by hand.

Sebhatu devised a mechanism that converts the rotary motion of a drill to the linear motion of an oscillating multitool (OMT). The blade in an OMT moves only a fraction of an inch per stroke, yet is able to cut because the tool produces thousands of strokes per minute—a technology devised in the 1940s by an orthopedist who wanted a faster safer way to remove plaster casts.

The QuadSaw differs from the OMTs found at tool stores in a couple of ways—it's a drill-powered attachment, and it has four blades that cut at the same time. The blades in a single-gang model cut a square opening for the electrical boxes (approx. 3" x 3") used in Sebhatu's adopted country, the UK. A second model cuts rectangular openings for larger (dual-gang) boxes.

How a standard OMT transforms rotary motion to linear action.

Unlike the blade in an OMT—which moves in response to an eccentrically mounted bearing—the blades in the QuadSaw are driven by a spinning cylinder with a sine wave shaped channel machined into it. Each blade is attached to a "block" with a diagonal slot in the back of it. The slot houses a captured bearing that drives the block back and forth in response to the up and down motion of the bearing as it traverses the channel of the rotating cylinder. It's a brilliant way to convert rotary action to linear motion while transferring power to four blades at once.

How the QuadSaw works: Captured bearings (30 a-d) slide up and down in the slots through a fixed collar (61) as they traverse the sine wave shaped channel in a rotating cylinder (24a). The bearings also slide in the diagonal slots (46 a-d) in the backs of the blocks (26 a-d) to which blades (10 a-d) are attached, converting vertical to horizontal (oscillating) motion.

Moving in unison, the blades make quick work of drywall, leaving holes that are perfectly sized for retrofit electrical boxes. A "pilot bit" on the back of the device prevent it from sliding when the blades first make contact. An adjustable "leg" allows the electrician to preset the height of holes he will cut.

The QuadSaw was patented and developed by Genius IP and is set for release in the UK in the summer of 2017. The company is said to have models sized for the electrical boxes used in the US. The tool is expected to sell for £199 (about $220 USD). That's a lot to spend for a hole cutting attachment but could be worth it to the electrician who regularly installs old work (retrofit) boxes in drywall.