As residential and commercial builders and remodelers, we install a mind-boggling amount of steel to meet the stringent seismic requirements of the California building code. To make mechanical connections, we drill 1/2-inch- to 1-inch-diameter holes through steel I-beam flanges up to 3/4 inch thick and steel plates up to 1 inch thick. Until 2009, we bored these using standard high-speed-steel twist drills. Each took about an hour, and we could go through hundreds of dollars' worth of drill bits per job. Then, following the lead of local ironworkers, we started using a Hougen HMD904 portable magnetic drill with Hougen Rotabroach annular cutters.
At 27 ½ pounds, it's one of the lightest magnetic models on the market and can bore holes from 7/16 inch to 1 1/2 inches in diameter, up to 2 inches deep. To use the drill, you position it on the material, press the rocker switch to turn on the magnet, push an adjacent button to turn on the motor, and rotate the feed handle to power the bit through. We squirt cutting fluid on the cutter before drilling each hole.
With the HMD904, we now drill an average hole in about two minutes. The annular cutters are reasonably priced (an 11/16-by-2-inch cutter costs around $50). They typically drill more than 100 holes before they dull, and they can be resharpened. Like hole saws, the annular bits cut a plug out of the material (photo, above right), which means they convert far less solid steel into chips than standard twist drills do.
When using this tool, we always keep a handhold, in case the tool lets go. If working high up, we strap it to the work with the included chain. We learned that lesson the hard way: A mag drill once fell 20 feet when its power cord unplugged, smashing onto the rocks below.
—Sim Ayers owns SBE Builders, in Discovery Bay, Calif.
