Cool Tools: Hole Saws
Published: January 2009
Hole saws can quickly cut clean, round holes in studs for cabling and conduit to pass through, holes for lighting fixtures, and knockouts in electrical boxes. Hole saw products today can and must cut through many types of materials.
These hollow cylinders with cutting teeth on the bottom edge are available in a variety of sizes. Their appearance may not have changed much over the years, but today’s hole saw products are made from materials that are more durable. Tooth designs cut faster and cleaner and last longer. Sizes range from ?-inch to 6 inches with products for cutting through wood, steel, aluminum, plastic and fiberglass. Adjustable hole cutters are a relatively new variation. These are available in models that can make holes as large as 18 inches in diameter.
Hole saw features
LENOX, Anna Whitton, senior product manager, drilling said: “The best general purpose hole saws manufactured today are bimetal with edge materials high in cobalt concentrations. Other general trends in hole saw designs include aggressive tooth angles to enhance performance in sheet metal and stainless steel, quick change hole saw arbor systems, specialty hole saws optimized for specific materials, greater emphasis on cost per cut and productivity.
“Most hole saw manufacturers offer a standard arbor connection system between the saw and the drill. Standard arbors offer ½-inch thread for the smaller sizes and ?-inch thread for larger size hole saws. An arbor with a pin that engages the hole saw cap offers the best strength in the field, especially on hole saw sizes larger than 4 inches. While there are some quick-change systems on the market, most of these systems sacrifice speed of changing from one saw to another for strength of connection and has led to accuracy problems and quality of cut issues.
“The most important features for professional users are the number of holes that a hole saw will make before wearing out and the speed at which a hole saw makes the hole. For bimetal hole saws, the ability to cut many materials effectively is important. For specialty hole saws, the performance of the hole saw—life, speed, etc.—in the applicable materials is most important. Consistency of performance is always a key factor.”
GREENLEE TEXTRON, Brian Allison, senior product manager said: “There are several different types of bimetal hole saws and high-speed steel cutters on the market today made of better, more high-tech materials that last longer and cut faster and cleaner. Quick-change arbors provide faster hole saw change-out, easier slug removal and a safer way to drill using hole saws.
“Quality bimetal hole saws have a design where the body of the saw is made of a softer metal that resists fracturing, while the teeth are made of a high-speed tool steel, such as a high-grade 8 percent cobalt M42 that can withstand heat and maintain sharpness, providing much longer life than lower grade steel hole saws. Also, look for hole saws that feature an arbor with a solid no-gap connection between the arbor and the hole saw. This usually includes a special sliding collar that locks up against the hole saw back plate, thus eliminating vibration that could lead to premature wear, tooth fatigue and ragged holes.
“Electricians generally use hole saws ranging in size from ?-inch through 4 inches. Electrician’s kits provide an assortment of the most commonly used variable pitch hole saw sizes and arbors.
“Metal and wood continue to be the most common uses for hole saws. For cutting through wood, look for a hole saw with an increased pocket depth and increased height of the spurs relative to the cutting edge. This helps evacuate wood chips faster and easier for cleaner holes.”
BOSCH, Jon Howell, product manager, linear edge accessories said: “The majority of hole saws on the market today are bimetal because they are cost effective and provide good results in a number of common construction materials. Addition of an 8 percent cobalt alloy increases resilience and extends life. Progressive tooth patterns provides better contact with the material being cut and better chip clearance for faster, uninterrupted cutting compared to standard tooth geometry and also extends life.
“Recently, manufacturers have introduced a number of specialty hole saws that tackle more specific cutting applications. Sheet metal hole saws are equipped with a spring for automatic material ejection, variable tooth pitch that is optimized for fast, precise cutting and a lipped edge that acts as a safety stopper, which prevents breakthrough and leaves the work surface intact. Carbide hole saws have diamond-ground carbide teeth that are extremely robust and durable with drop-shaped chip clearance slots for fast, uninterrupted cutting. Carbide hole saws cut through wood much faster than bimetal saws do and also easily cut through difficult materials, like ceramic tile, brick and cinder block, cement board, fiber cement and plastic.
“Our quick-change adapter nuts and mandrels work with almost any manufacturer’s hole saw cups enabling users to move effortlessly between applications, sizes and materials and enables users to change cup sizes in seconds.
“Performance can be defined differently for each user, but it comes down [to] quickly and effectively making holes regardless of the material or size. Speed of cut and durability are important and can be influenced greatly by the material they need to cut. Evaluation of products should take into consideration the material and then find the hole saw that provides the best cost per cut while also meeting their needs for cut quality and ease of use.”
MAKITA USA, Joe Soto, product manager, pneumatics and residential construction said: “In general, bimetal hole saws account for the majority of hole saws sold in the U.S. They are preferred for their moderate price, versatility and widespread availability. Despite the lower price positioning, these products have improved substantially due to better materials—particularly the metal used for the teeth portion of the blade and also an improved welding process, which bonds the two pieces together more securely. The pilot drill and hole saw attachment can be interchangeable, and new pilot drills can be purchased and used with hole saws.
“Professionals, including electricians, generally prefer carbide-tipped hole saws for hard steel surfaces like stainless steel and sheet metal. Bimetal hole saws are good for all-around use, particularly wood, but users should always note the speed of the drill. Generally, the faster the rpm, the lower the torque, so the low-speed setting will deliver the higher torque needed to turn a bimetal hole saw in wood, particularly larger hole saws. Also, when cutting into wood at a higher rpm, it is more likely to burn the wood than at lower rpm.
“Carbide-tipped hole saws are commonly used for hard-steel applications like stainless steel, sheet metal and even plastic. When using carbide-tipped hole saws in metal, higher rpms are acceptable because the increased speed will heat up the material, effectively softening the cutting surface and speeding the cut.
“Both carbide tipped and bimetal hole saws are equally productive as long as the right product is matched with the right application.”
HOLE PRO (Lightsmith Inc.), Bruce Stenman, president said: “Adjustable hole cutters are fast and safe to use; minimize dust and shavings, making for quick cleanup; and can easily be adjusted to make the exact hole size needed for the job.
“Recessed lighting can sizes have expanded from four sizes for tungsten lamps to more than a dozen halogen can sizes, multiple PAR light can sizes and the emergence of LED light fixtures; [This makes] it difficult to effectively use fixed-size hole saws.
“More electricians are also called upon to install CO2 monitors, security devices and in-ceiling speakers, all of which require a wide range of cut out sizes. The larger the hole and the more holes that are needed for a given job, the more value an adjustable hole cutter provides, saving time in cutting, clearing the plug and minimizing the time spent in work site clean up.
“Hole cutters adjust to cut exact hole sizes needed with models available that cut holes from 2 to 6 inches, 2 to 9 inches, 2 to 12 inches and 2 to 17 inches. Replaceable blades keep the tool performing ‘as new.’
“Important features to look for include twin-blade design for balance to cut round holes in both short and hard materials, ease of adjusting hole size, quality blades for both abrasive materials and metals with a kerf designed for cutting smooth holes in wood tongue-and-groove ceilings, ease of use and durability, and that all needed components are in the kit, including the kit, shield, shield bearings, shield gasket, carry case, adjustment tools and instructions for use.”
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at firstname.lastname@example.org.