What Is the Difference in Forstner Bit Rims? a Clear Answer

Drill bits are used to drill small holes in woodworking, while bigger holes are created with hole saws, spade bits, or Forstner bits. There are occasions when a hole saw or even a spade bit is preferable, but there are also situations when a Forster bit is the superior option.

On the Forstner bit, the guiding rim is a crucial element. But when you check to buy this type of drill bit, you will notice that they come in three different varieties of Forstner bit rims.

The saw tooth is the first Forstner bit rim, which produces less heat but is more aggressive.
The second type is the continuous rim bit, which cuts very cleanly but heats up quickly.
In Between, there are wavy rim bits, which may cut quite aggressively while remaining quite clean without overheating.

Forstner bits cut smoothly with little tear up and provide a lovely flat bottom thanks to the guiding rims. Furthermore, they can be utilized to create long, overlapping gating holes or slots. This is one of the reasons why these drills are so popular.

Many people, however, are unaware of the many types of Forstner bit rims, and that every type will give them a different outcome.
In this article, you’ll learn about the three different types of Forstner bit rims, as well as some tips and methods for determining which type of Forstner bit rim to use for your projects.

Disclosure: At zero cost to you, I may get commissions for purchases made through links in this post. I earn from qualifying purchases as an Amazon associate. Products featured are selected based on quality, performance, and reputation, regardless of affiliate relationships.

What is a Forstner Drill Bit?

A Forstner drill bit is a type of drill bit that is circular with a flat bottom. Thanks to the spur point on the bottom, these drills are self-tapping and centering, which means you can drill perfect round holes with a flat bottom without pre-drilling.

These drill bits are capable of drilling exceptionally clean holes, which means that very little wood dust is produced.

The Forstner drill bit is an important tool to have in a workshop. It’s used for drilling holes in wood most of the time, but can also be used to drill into plastic. Different types of wood or circumstances require different types of drill bit rims, so you need to know what kind of bit you are looking for. There are three different types of Forstner drill bit rims: saw tooth, continuous, and wavy. Each type of Forstner drill bit is designed for a specific application, and that is what you are about to discover below.

The Difference in Forstner bit Rim Types

The most important feature of a Forstner bit is the guide rim. This is what severs the fibers around the perimeter of the hole to produce a clean entrance without tearing it up. Choosing the right guide rim can also help your Forstner bit stay sharper and last longer. The most common styles are usually saw tooth guide rims, continuous guide rims, and wavy guide rims.

I will go over these three types more in detail below, so you know exactly what Forstner drill bit to use when.

Forstner bit rim with saw tooth

Saw tooth rims produce less heat because only the points of the piece cut into the wood around the perimeter of the hole. This means that you can run a sawtooth Forstner bit at a slightly faster speed and cut a little more aggressively with it without overheating and dulling your drill bit.

A downside of this type of Forstner bit rim is that those saw teeth tend to chatter or shift a little on the surface of the wood at the beginning of the cut. This may tear out the fibers around the hole. Saw teeth also make it more difficult to work at an angle, and they produce a rougher cut when boring overlapping holes.

Continuous Forstner bit rim

Many of the issues that a saw tooth Forstner drill has to deal with do not apply to continuous rim bits. They are better for angled boring and overlapping holes because they cut the surface fibers and enter the cut more neatly. The disadvantage of this style of Forstner drill bit rim is that it generates more heat, especially on larger drill bits. So, with a continuous rim bit, you really need to manage your speed and not be too pushy, or you’ll rapidly dull it.

Wavy rim bits

Wavy rim bits are a type with the best of both worlds because they bridge the gap between the aggressive friction-reducing teeth of a sawtooth bit and the crisp, cutting knifelike edge of a continuous rim bit.
Wavy rim bits produce clean holes in pretty much all situations. They also seem to better break up the chips within the hole, so they may be objected more efficiently to further reduce heat buildup.

Choosing the Right Forstner Rim For Your Project

The wavy guide rim is, in my opinion, the ideal option when making a choice based on the Forstner bit rim.
This guide rim doesn’t heat up fast, assures clean cuts, and is nevertheless a drill bit that cuts aggressively.
As a result, this type possesses all of the beneficial characteristics of the other two types.
However, in some circumstances, a different Forstner bit rim type may be preferred. You can best estimate what you’ll need for your tasks and make the best decision using the information on this page.

When using a larger bit, regardless of the rim you choose, you must slow down your drill speed. Under the belt cover of your drill press, there should be a speed chart. You may also read the article “What Drill Press Speed Should I Use? (+Drill Press Speed Chart),” which explains how to establish the proper speed for every drill.

If you’re using a handheld drill, choose one with a variable speed setting. Partially pulling the trigger can also be used to regulate the speed. This may assist to slow down the process and keep it colder.
Allow the drill or the Forstner drill bit to cool down every few minutes if you detect the drill or the drill bit heating up. You can also make it a habit to raise the drill out of the hole every now and then to assist rid the hole of chips. This will keep the bit cooler and protect the wood from burn marks.

Where to find the type of Forstner bit rim I need?

On Amazon, I was able to find complete sets of each of these Forstner bit rims types. With a complete set, you’ll be able to handle the majority of tasks. Although some are not cheap, buying the drills separately would be much more expensive, therefore buying a set is cheaper, despite the relatively high price.

You can use the links to find the drill set that best matches your needs. Keep in mind that in this situation, price and quality go hand in hand. Buying drills is something I don’t cut corners on, since I’ve learned that if I have to buy twice, I end up spending a lot more.

To dive deeper into drill bits, specifically into specialized boring tools in carpentry, you should visit my article, 6 Commonly Used Boring Tools in Carpentry (You Should Have). This article will let you discover tools to take your woodworking skills to the next level.