When creating holes in wood, there are different drill bits and devices that can do the job. Two of the most common are the Forstner bit and the hole saw. Both are used to create holes in materials for a wide variety of uses.
What is a Forstner Bit?
A Forstner bit is a drill bit designed to drill into softer materials. It has sharp point at the center that looks similar to a brad point bit. The flat cutting edges in the center resemble the spade bits. In addition to this, a Forstner bit has two radial blades with cutting edges on the periphery.
Depending on the bit that is used, you can drill holes either all the way through or only partially through materials. Plus, you can create overlapping holes, angled or pocket holes, and put notches on the edge of materials as well.
The Forstner bit is superior to standard drill bits in terms of creating neat holes in wood and softer materials. Standard drill bits tend to leave rough edges which is not desirable in certain types of work. Plus, the Forstner bits can create angled holes with greater efficiency. This means that for creating certain projects, the Forstner bit is not only superior but easier to use in such cases.
Why is it called a Forstner Bit?
The bit was named after Benjamin Forstner who was a gunsmith. Forstner patented his bit in 1874, a time in which many gun stocks along with grips were fitted to each weapon by hand. Because this required considerable accuracy, special tools, and bits were developed to make the job easier to accomplish in a reasonable time.
Mr. Forstner was determined to create a new drill bit that could make accurate, clean holes in wood, and generally be superior to the auger bits invented by Russell Jennings which were common at that time. He succeeded in accomplishing his goal of creating a bit that could bore smooth holes into wood and his invention worked whether the center spur was engaged in the workpiece or not.
Forstner managed to succeed by creating a bit that was not only superior but quite versatile. The result was that Forstner bits became popular around the world not only for gunsmithing but for other projects in which smooth, clean holes were needed.
What is the Purpose of a Forstner Bit?
Over the years, the Forstner bit has been improved upon in terms of creating holes with smoother lines at a faster pace.
The primary purpose of a Forstner bit is to create clean, flat bottom holes on a piece of wood. It can also be used for drilling overlapping openings, large diameter holes, and angled holes. These bits are also useful in cutting through wood veneers cleanly.
Have you noticed that the brad-point created a mark in the center of the round pocket?
You could use a Frostner bit to make counterbores. You just have to do the counterbore first and then drill the screw hole.
One downside of traditional Forstner bits is that they tend to clog depending on how much material is cut. Plus, they also tend to burn the wood because of the heat generated by the bit. Colt bits are an improvement since they do not clog in the same manner and have a scoring tooth which helps prevent burning.
Another variation is the multi-spur Forstner bit or the sawtooth bit with a special tooth design. If you are using the traditional version, start with slow speed and feed and increase the rpm once the cutting blades have penetrated the material.
What is a Hole Saw?
Sometimes called a hole cutter, this is also a cutting bit but with a unique design. This tool has a pilot drill in the center and a cylindrical saw with peripheral cutting teeth.
It has the appearance of a soup can with the teeth on the facing end. This annular shape cuts a hole into the material when pressed into the surface.
Extending from the center of the hole saw is a drill bit that cuts into the core material first, this provides a smooth guide for the hole saw which follows and cuts through the entire material. The material which has been cut will be inside the can once it is removed. If you want to use the round piece that is cut out, you can use the hole saw without the pilot bit as well.
This type of saw must cut entirely through the material, otherwise, it will only leave a ring with a hole in the center. The major advantage of a hole saw compared to conventional saws is that the material can be removed cleanly and efficiently. This means that it requires less power compared to a standard saw while cutting out more material compared to a Forstner bit.
Hole-Saw Sizes
The hole-saws are available from ½-inch up to 8 ¼–inches (13mm to 210mm) in diameter. However, 3/8-inch to 5-inches sizes are the most common bits available. For the majority of my woodworking jobs, I use a twist drill or spade bit for holes smaller holes.
They are available as the non-arbored version set or single bit that has a fixed arbor (usually ⅜″ hex shank).
Material
The hole-saws are available in high carbon steel, high-speed steel (HSS), and bi-metal that can cut through softwood, hardwood, plastic, plasterboards, drywall, etc.
You can also get carbide-tipped cutters for penetrating through metals such as aluminum.
Using Forstner Bits Instead of a Hole Saw
While both bits do similar work, there are important differences that you will need to know before starting your work.
Hole Size
The size of a Forstner bit varies from ¼-inch up to 2 ¼-inches. This is generally smaller compared to a hole saw which can cut holes from 1” up to 6” depending on the size that is used.
Hole Depth
The depth of the hole will depend on the length of the bit or saw that is used. For Forstner bits, the hole will be flat bottomed, but also will punch through depending on the depth of the material. A hole saw will only cut holes through the material that is used.
The real difference starts when you want to drill deep holes. With Forstner bit, you can use an extension to cut deeper.
Quality of Cut
Both will cut clean holes into the material compared to rough holes created by regular bits. Of the two, the Forstner bit will cut the cleanest hole thanks to the design of the bit. The hole saw will also cut with a good finish, but it will not be quite as neat compared to the Forstner bit.
Speed of Cutting
Here, the hole saw has the advantage because it can cut faster compared to the Forstner bit. Although the speed of the cutting is not as fast compared to a spade or paddle bit, you can complete the job faster using a hole saw. Forstner bits take more time to get a sharp, clean hole.
In the end, whether you use a Forstner bit or a hole saw will depend on the type of job you are trying to do. A Forstner bit is better if you are making small, precise holes for your project. A hole saw is superior if you need to make holes larger than 2 1/4”, need to punch through the material, and need to complete the job quickly.
Cost of Bits
Forstner bits are cheaper compared to hole saws and create a cleaner hole with edges that are better defined as compared to a hole saw. However, the hole created will be smaller and you might run into issues with burning or clogging. This changes if you use the more advanced Colt bit which does similar work compared to the Forstner bit, but without the burning or clogging issues.
Can I Use a Forstner Bit with a Hand Drill?
You can use a Forstner bit with a regular drill or a cordless drill. The brad point tip in the center enables you to locate the hole and prevents it from wandering.
However, if you are drilling overlapping holes or enlarging an existing hole, it is better to do it on a drill press, milling machine, or lathe.
Conclusion:
Which one you choose will depend on what you desire in terms of drilling holes into materials. Keep in mind the limitations of the hole saw as the hole must go all the way through. The Forstner bit can stop and leave a flat-bottomed hole in the material without having to go all the way through.
Dan Miller is a professional toolmaker with extensive experience in the metalworking and tooling industry.
An avid DIY enthusiast and passionate hobbyist woodworker, Dan shares his expert knowledge here.