A step drill is often the cleanest way to enlarge a hole in thin sheet metal, especially when the new hole is only a few sizes larger than the old one. Its stepped cones cut progressively, so the sheet is less likely to grab than it would with a large twist drill. But the bit … Read more
The quick verdict For smooth, round holes in thin aluminum, a step drill is usually the easier choice—especially for holes larger than about 6 mm (1/4 in.). Its stepped cutting edges enlarge the hole in stages, which helps limit grabbing and makes it easier to stop at a chosen diameter. A twist drill is the … Read more
The short answer For repeated holes in thick steel plate, a Rotabroach-style annular cutter is usually faster, cleaner and less tiring than a twist drill. It removes only a ring of metal, leaving a slug, instead of turning the entire hole into chips. That matters when you are drilling dozens of holes through 1/2-inch, 3/4-inch … Read more
Field fabrication in a remote location changes what matters in a magnetic drill. Shop power is unavailable, extension cords are a trip hazard, and a damaged cutter or flat battery may be hours away from replacement. The best cordless magnetic drill is therefore not simply the fastest machine. It needs dependable holding power, useful battery … Read more
For stainless plate, the choice between carbide and high-speed steel (HSS) annular cutters comes down to hole size, plate thickness, machine rigidity and how many holes you need to make. Carbide usually cuts faster and lasts longer in production work, but it costs more and is less forgiving of vibration or a poor setup. HSS … Read more
Quick answer For annular cutters drilling mild steel, use a cutting fluid made for metal cutting—not ordinary motor oil or a general-purpose spray lubricant. For most shop and site work, a sulfurized cutting oil is a dependable choice: it clings to the teeth, reduces heat and friction, and helps carry chips out of the cut. … Read more
Why Vertical Magnetic Drilling Is Riskier A magnetic drill can stay attached to a vertical steel plate while drilling, but the magnet is not the only thing you need to manage. The drill’s weight pulls straight down, while the annular cutter creates torque and side load. Chips can also pack into the cut, and a … Read more
Start with the hole, not the cutter An annular cutter removes a ring of metal, leaving a solid slug. That makes it faster and less demanding on a drill than a twist drill of the same diameter, especially for larger holes in plate. Choosing one comes down to two separate measurements: the finished hole diameter … Read more
Quick verdict The Hougen HMD904 and Milwaukee 2788-22 are both portable magnetic drills for boring holes in steel, but they suit different jobs. The HMD904 is a corded drill built around steady, controlled production work. The 2788-22 is a cordless system that trades unlimited runtime for easier setup and access to places where a cord … Read more
For bolt holes in a steel beam, an annular cutter removes a ring of metal rather than grinding out the entire hole. That usually means a cleaner edge, less cutting time and lower tool load than a twist drill of the same diameter. The best choice depends less on a brand name than on hole … Read more