Published In November 2001
Blades Hole saws are veritable electricians’ workhorses. Used with electric drills, they expedite cutting holes in a variety of materials, including steel, copper, aluminum, brass, bronze, wood, and plastic. According to Rob Pierson, product manager, Greenlee Textron, electricians use hole saws about 73 percent of the time to drill holes in products made from mild steel, such as electrical panels and enclosures. Hole saws bore holes into wood or metal by cutting away the narrow bands of material around the perimeter of the hole saw, minimizing the amount of material that must be removed. They last, on average, between 50 and 150 holes. Most electricians work with bi-metal hole saws for drilling into a range of work materials, including wood, nail-embedded wood, plastic, and any machine-able metal, including stainless steel. A bi-metal hole saw consists of high-speed steel for wear resistance, welded to a tough alloy steel for strength. Some hole saws feature carbide tips, which are suitable for tough materials such as stainless steel and fiberglass. Carbide is very hard and holds up well against the heat generated by sawing. Other tip options include grit or carbide grit, which leave a smoother finish on both sides of ceramic or other abrasive types of material. Also available are economy-priced, plain carbon hole saws, which do not have high-speed steel edges and are less durable; and synthetic diamond-tipped hole saws, used on ceramic. Hole saws are typically available in sizes ranging from 9/16 inch through 6 inches. In hole saws, as in baseball, the pitch matters. Pitch, in tool vernacular, refers to the number of teeth per inch (TPI). Variable pitched teeth, with alternating numbers of TPI around the circumference, are a popular option because they reduce vibration and also yield smoother cuts and less operator fatigue. A 4/6 variable pitch design is a common configuration because it reduces harmonics while drilling in steel, but manufacturers offer variations. To help prolong the life of a hole saw, follow recommended cutting speeds. In general, speed should decrease as hardness increases—cut wood, plastic, and other soft materials at high speeds and stainless steel at slow speed. LENOX hole saws, from American Saw & Mfg. Company, sport a patented variable tooth design that features alternating blade sections of 4.5- and 5.5-teeth/inch which, said the company, evenly distribute cutting force over all the teeth. This design maximizes cutting efficiency in thick- and thin-gauge materials without sacrificing cutting speed, cut quality, or tooth strength, Lenox noted. The varied heights and set pattern on the teeth allow the saw to take smaller, more uniform pieces of material per tooth. Each tooth working independently improves the hole saw’s life and efficiency over the more traditional method of having one front tooth plowing into the material and wearing out fast, noted Corey Talbot, product manager for hole saws at Lenox. Greenlee Textron recently introduced a bi-metal hole saw with ¾ variable pitch which, said the company, improves performance and cuts holes in mild steel about 20 percent faster than conventional pitch hole saws. The high-speed steel teeth resist fracture during cutting, and the relatively thick back plate results in less chatter than a thinner back plate, Pierson said. The saw features a steam oxide finish that resists rusting and melting like paint when heated and won’t bind with chips when the saw is drilling into wood. The arbor sports a solid “no gap” connection between it and the hole saw. A sliding collar locks up against the hole saw back plate, eliminating vibration that could lead to premature wear, tooth fatigue, and ragged holes, said the company. Milwaukee Electric Tool Corporation’s 17-Piece 4/6 Deluxe Electricians’ Kit (49-22-4086) includes 12 different diameter bi-metal (with cobalt) 4/6 hole saws ranging from 5/8 to 3 inches, two arbors, and three ¼-inch high-speed pilot drills, housed in a sturdy plastic case. The variable pitch saws feature 3/16-inch thick steel backs on 1½-inch and larger diameter saws. The thick backs eliminate the need for driving plates and prevent drive pinholes from elongating, pointed out the company. The Matrix II (with cobalt) high-speed steel teeth are electron beam-welded to the body. Greenlee Textron’s new High-Speed Cutter features a solid high-speed steel body which, said the company, supports longer life, less tooth breakage, a more rigid connection between the cutter and the arbor, and a shallow cutting depth of ¼ inch. The cutter does a cleaner cut than a hole saw because the teeth are all ground, as opposed to being milled, and leave no burr, explained Rob Pierson, senior product manager at Greenlee Textron. The cutter has a life expectancy of 10 to 20 times more than a bi-metal hole saw. Makita USA offers carbide-tipped hole cutters that have randomly spaced tips to reduce chattering. The center bit is available in cobalt, suitable for cutting sheets of stainless steel, galvanized iron or aluminum, or tungsten carbide tipped, suitable for drilling glass fiber panels, PVC panels, and ceramic. Designed for rotary drills, the cutter has a built-in stopper that prevents it from penetrating further. The cutter is available in 20 sizes, with cutting diameters ranging from 5/8 to 3 inches. Gardner Bender Specialty Knockout Punches and Dies are designed for punching precise holes for specific knockout projects such as instrument panels, switches, keyways, and other data communication applications. Each product’s multi-point design evenly crimps the slug, saving physical effort and time by allowing it to conveniently drop from the die, pointed out the company. The multiple cutting tips also extend the wearability (cutting life) of the edges. A proprietary sealed-bearing design extends the life of the drive screw’s thread by reducing friction during use. High-carbon steel construction helps extend product life five times longer than standard steel punches, noted Gardner Bender. Each punch, die, and drive screw is sold in a combo set. Bits Marked step drills make it easy to drill holes of different diameters with one tool, or work up from a small hole to a larger hole without changing bits. They are also handy to deburr less-than-perfect knockout holes in conduit boxes. Klein Tools Unibit Step-Drill bits are suitable for drilling into steel, brass, aluminum, copper, and other metals up to 1/8-inch thick. According to the company, the single-flute design of the Unibit drill bit eliminates skidding, and the hole is automatically deburred by the next-larger size on the bit. Markings on the side of the bit identify each hole size. Klein Tools offers 10 models that fit into ¼-, 3/8-, and ½-inch electric drill chucks. The bits are handy for drilling knockouts into panel boxes, cabinets, and lighting fixtures. The bits give off an audible pop after each step. American Tool Companies’ UNIBIT step drills, available in a variety of sizes, feature a single-flute design that, according to Daryl Linnert, product manager, shaves the inside diameter of the hole as it drills into the material, so the shavings readily come out of the concave flute without bogging down the bit. The single-flute step drill cuts more evenly than a double flute, allowing the worker to “feel” each step, creating a virtually true round hole, he pointed out. Hole diameter sizes are laser-marked inside the flute. The IRWIN (American Tool Companies, Inc.) SPEEDCOR Bit features patented cutting spurs with internal grooves that, said the company, leave a smoother hole finish in hardwood, softwood, treated lumber, or manufactured lumber. A new short-length version (4¾ inches long) allows users to drill between studs without the need for a right-angle drill. The new Quick-Change SPEEDBOR Extension, available in 6- and 12-inch lengths, extends the length of the standard wood bit. The extension also accepts all power screwdriver bits and nutsetters. For rough wood drilling, DeWALT Industrial Tool Co. offers new self-feed bits with cutting blades and resharpable edges to go through wood quickly with a clean finish. An aggressive self-feed tip, which is replaceable, pulls the bit into the wood, and the bit’s teeth clear material out of the hole, the company pointed out. Bit sizes range from 1 inch to 45/8 inches in diameter. All the bit shanks are hex shaped and fit a ½-inch drill chuck. Heat-treated and brazed for consistent thorough hardening of the steel, Ideal Industries’ new line of masonry drill bits feature a durable tip that, said the company, is suitable for the toughest applications. The Ideal Industries Rotary Hammer Bit has a hard high-quality carbide tip for retaining a sharp cutting edge for drilling masonry materials. The Ideal Industries SDS Percussion Bit, for SDS and SDS-plus rotary hammers, sports a double fast-spiral fluting, engineered for efficient dust removal that, noted the company, results in faster drill time and virtually no bind in the hole. The bits undergo a special heat-treating process design to help ensure long life on extra-hard and abrasive materials. HILTI TE-CX masonry bits, for rotary hammer drills, feature large-flute gullets and solid carbide heads on sizes from 3/16 through ½-inch in diameter. These bits are suitable for drilling into masonry, concrete, and brick. The solid carbide head allows for rounder holes and longer bit life, and offers some rebar resistance, according to the company. The large double-helical fluting allows for increased drilling speed, faster dust removal, and less contact area with the hole surface, reducing friction and helping to increase the overall drill bit and hammer drill life. Stanley Power Tool Accessories (Jore Corporation) 73-Piece Fast-Change Drill & Drive Set includes a range of universal ¼-inch hex shank drill bits and accessories for wood, metal, and masonry, along with diverse screw driver and nut driver bits, and a Stanley Fast-Change AUTO LOAD connector for quick switching from drilling to driving without requiring re-chucking of the drill. The set includes a versatile drill slip and drive system used for drilling pilot holes, countersinking, and driving screws in applications where they require recessing. The set also includes a high-torque ratcheting driver handle. The drill bits feature 135-degree split points that reduce “skating” when starting a hole. The FELDMANS provide Web content for companies and write for magazines, trade associations, building product manufacturers, and other companies on a broad range of topics. They can be reached at email@example.com or (914) 238-6272.