Hole Saw Overview
Which Hole Saw Is Right for Your Application?
There are plenty of ways to make a hole in a variety of materials – it really comes down to is how large the hole needs to be, how many holes, how clean the cut needs to be and how quickly it needs to be cut.
For very clean holes in finish wood work, a forstner bit is my first choice cutter. Running electric lines, an auger bit or spade bit can make short work of numerous holes where the quality of the cut will be hidden behind the walls. For most applications in-between, the hole saw is a great tool.
Hole saws generally consist of a pilot bit, arbor and the saw or, in other terms, the cup. They range in size and most manufacturers offer 9/16” – 6” and there are some that go up to 6-7/8” for cutting holes in drywall for recessed lights.
While the cup does most of the heavy lifting, it is the pilot bit that ensures that the cut is centered and kept in alignment to produce a clean and consistent cut. Most bits are 135-degree high-speed steel (HSS), also there are a number of specialty bits such as cobalt bits for sheet metal and self-starting diamond bits for tough materials.
Since hole saws are used in a wide-array of applications, the materials and configurations are equally diverse.
Bi-metal HSS (high speed steel) is the most common type of hole saw due to its ability to cut numerous materials including wood, PVC and some metals.
Need a little extra kick? Throw in some carbide. There are two main types of carbide hole saws – grit and tipped. Tipped is basically has a HSS tooth configuration with an infusion of carbide that helps power through tougher materials while providing greater longevity. Grit employs a squared profile, similar to a segmented diamond saw blade. Also, this configuration features fewer teeth that have deeper gullets for easier material removal.
Tungsten carbide is another option. This compound can withstand high heat caused by abrasion which makes it an ideal for stainless steel applications. Its cutting strength and durability also lends itself to cutting certain masonry and brick.
Diamonds are one of the hardest known natural materials and when cutting dense stones such as marble or granite, they are the go-to choice for cutting openings in counter tops, commercial grade tile and stub outs in bathrooms or kitchens. They can be continuous, grit or tipped.
Continuous hole saws are often difficult to use due to lack of pilot bit. This means that the cup has to be angled with only a small portion making contact with the material and once a small groove has been established, the drill and bit need to be brought upright.
Most hole saws have a fixed or variable tooth configuration. Common fixed pitches are 3,4, or 6 teeth per inch (TPI). Variable-pitch blades, such as 4/6 or 3/4 TPI, feature teeth that get bigger or smaller with less or more space between them at regular intervals around the blade. Though the designation may read 4/6, the length of each segment might not be an entire inch in length. The variable pitch helps with debris removal and reduces cutting vibration.
For multi-construction bits that incorporate carbide, the generally feature a couple of teeth and have a very long gullet that encroaches on the base of the cup. Since these saws are working on harder surfaces, it is more important to have a constant air flow where the material being cut is quickly moved from the cutting surface for better performance and to keep the cup cooler.
Almost all cups will have slots cut out to help with heat dissipation as the cuts gets extremely hot. Additionally, some companies incorporate a small circular hole for plug removal.
If there is one big disadvantage to hole saws it is removing the cut material. As just mentioned, these things get really hot and either wear gloves or wait until it cools There a few options companies have incorporated to make the process easier: some companies have included a spring for plug ejection, this is handy when cutting sheet metal. One company has a steeped slot where users can insert a screwdriver while another company has a push-button built into the arbor where users depress the button and move the cup back to expose the plug.
For contractors, the best bet is to get a hole saw kit. This a great way to get a range of hole saw sizes for the most common applications and once you have the mandrel, pilot bit and arbors, it is easy to purchase a single cup once it needs replaced.
