While ordinary drill bits are quite efficient, their cutting action can create ragged holes, particularly when working with larger sizes. You could use a spade bit, but they often vibrate or “chatter” and can be difficult to control.
Some techniques can overcome the problem, but the simple solution for making neat, precise holes is a Forstner drill bit. It has a central point called a spur that is designed for accurate positioning, sharp cutting teeth, and wings to clear waste. As a result, there is seldom the need to cut deep holes in several stages, as you do with standard twist drill bits.
A major advantage of a Forstner bit is that it’s made to drill flat bottom holes. Rather than drilling all the way through, a flat bottom hole has smooth sides, a small pilot point in the center, (and the name suggests) a flat bottom. These are great for dowel joints, or fitting catches in cabinet doors. Unlike a spade or twist drill bit, Forstner bits have no problem cutting at an angle and can drill partial or overlapping holes. The latter makes for fast material removal when cutting mortises, particularly when used in a drill press. Forstner bits are also popular with woodturners, allowing large, deep holes to be cut on a lathe.
While available singly, Forstner bits are usually sold as boxed collections of eight or more. The best Forstner bit sets offer tremendous flexibility, great versatility, and excellent value.
BEST OVERALL: Freud FB-100 16-PC Diablo Forstner Drill Bit Set
BEST BUDGET: INTOO Forstner Bit Set 8 pcs Wood Drill bit Set
UPGRADE PICK: Freud 16 Pcs. Precision Shear Forstner Drill Bit Set
BEST CONTRACTOR SET: PORTER-CABLE Forstner Bit Set, 14-Piece (PC1014)
BEST SAWTOOTH SET: Steelex D3573 Forstner Bit Set with Hex Shank
BEST METRIC SET: Meichoon Forstner Drill Bit Set 15-35mm 16 Pcs
BEST FOR HAND DRILLS: Forstner Bit Set, Wood Drilling, w/Carbide Tipped 8 Piece Set
BEST FOR HARDWOOD: IRWIN Marples Forstner Bit Set, 14-Piece (1966893)
BEST VARIETY: 20Pcs Forstner Drill Bits, Rocaris Tungsten Steel
HONORABLE MENTION: Forstner Bits Set, BASYNOL 5Pcs Forstner Drill bits Set
What to Consider When Choosing the Best Forstner Bit Set
At first glance, all Forstner bits appear very similar. However, there are differences in the materials used, and the design of the cutting edges. While these dissimilarities may be seemingly minor, they can make a big difference to efficiency. When selecting the best Forstner bit set, pay attention to its size to ensure it’ll cover the range of tasks you need it for.
The standard Forstner bit has two individual teeth on the perimeter. These teeth are located directly opposite each other and are designed to cleanly slice through wood fibers as they rotate. The width of this tooth varies—on some, it’s slender, while on others it might be as wide as ¼ the drill bit circumference. A longer edge increases cutting speed and a bar across the center pushes the waste out of the way as the bit rotates. A central spur, which is just a fraction of an inch longer than the teeth, allows for precise positioning.
Saw-tooth Forstner bits have a series of teeth that resemble a coarse saw blade. These are designed for more aggressive cutting and are particularly good for end grain. The Precision Shear design, which was introduced by Freud has a serrated edge with a steep interior angle that produces a very sharp edge, and rapid, chisel-like cutting action.
The majority of Forstner drill bits are made of High Speed Steel (HSS). HSS drill bits are typically titanium-made drill bits and have a titanium oxide coating. They’re durable, resistant to corrosion, and can drill through wood and steel.
However, with frequent use, HSS bits tend to lose their edge quickly. The solution is to add tungsten carbide tips (often referred to as carbide, for short). These tips are then bonded onto the body of the bit, resulting in an edge that stays sharper for much longer. With a carbide tip, the bit will be capable of cutting materials like aluminum or tile.
Many DIY users will be fine to use HSS bits on their own. However, professionals or individuals who use these tools frequently may want to invest in a carbide Forstner drill bit set.
One or two manufacturers use High Carbon Steel (HCS). HCS is slightly softer than HSS, though the term “softer” has to be taken into context. These bits are still hard enough to drill into wood and wood-based materials. HCS bits won’t cut aluminum and other soft metals, or tile and masonry.
Bit Size & Number of Bits
A standard twist drill is fine for drilling holes of small diameters, so Forstner bits are not usually found below ¼-inch. Sometimes, the smallest bit in a set will be ½-inch. The largest is usually 2 to 2 ⅛-inch. Although larger Forstner bits are available, they’re usually sold individually as they’re bigger than most people need. Metric Forstner bit sets are also available. These can be very useful when fitting cabinet hinges, for example, as the hardware is often metric. Imperial bits can be close to the same size, but not close enough for a good fit.
Oftentimes, two sets will come with the same minimum of maximum sizes—one may contain eight bits, while the other has 10 or 12. The latter of the two sets will have a greater variety of sizes, thus increasing versatility. However, it’s important to consider quality. While a large number of bits at a low cost might suit the DIY user, this set is unlikely to meet the standards of a professional.
Most Forstner bits have a round shank, though a few have a hex shank. While the latter does provide a stronger grip, it’s rare for round shanks to slip—especially if the chuck is tightened correctly.
Forstner bit sets are usually supplied within a box or case, but the quality varies. For example, if the bits are improperly placed, the teeth may knock together and become damaged. Some boxes display the bits upright, making it easy to select the one required.
Forstner bit extenders can increase shaft length, offering a potential hole depth of 8 inches. Extenders are particularly popular with woodworkers for boring out the center of vases, for example. Extenders come in different diameters and some will only fit ½-inch chucks, so compatibility should be checked beforehand.
Frequent users may want to consider purchasing a Forstner bit sharpening set, as well. Unlike sharpening standard twist drills, the job can’t be done with a bench grinder. Sets include flat and round files, plus a grinding burr suitable for a rotary tool. If the Forstner bits are carbide, the sharpening set will need to be diamond coated.
Re-post from https://www.bobvila.com/