How to Choose Router Bits


No doubt, a router is a woodworker’s best friend.
No doubt, a router is a woodworker’s best friend.

­Wood may be one of the easiest building materials to work with (as opposed to, say, plastic or metal), but it still leaves something to be desired. You can't shape it with your fingers and mold it into whatever shape you want. The only way to form a solid piece of wood into something else is through the art of addition and subtraction. You take away little pieces and add on other pieces until you get the shape you want. In the past, people accomplished this with chisels, hammers and planers. Luckily in the modern age we have routers, which we can use to shape wood in a relatively small amount of time.

No doubt, a router is a woodworker's best friend. It might just be the most versatile tool you can own -- but in a world without router bits, it would be nothing more than a spinning motor. If you've ever looked at the detail on the edge of a table or a paneled door and wondered how it was made, wonder no more. It was done with a router, and the specifics of the detail depend on the router bit you use.

­There are a wide variety of different router bits out there, and they've all been shaped and perfected over the years to serve specific needs. There are router bits used to add detail, router bits used to make grooves and notches for joinery, and router bits for writing in wood. The list goes on and on.

The thing to keep in mind is that not all router bits are created equal. Not only are they made out of different materials, but their quality can differ greatly. At the end of the day you could own the best router on the market and be the most experienced woodworker in the world -- and still end up with sloppy results if you used a bad router bit.

Read on to learn about the basics of choosing a router bit. You'll learn about common types of router bits, shank diameters, drill speeds and what makes up a quality bit.

Common Types of Router Bits

The more you work with a router, the larger your assort­ment of router bits is bound to become. There is an almost endless variety of router bits out there. But if you're starting a collection, you may want to start by stocking up on these common bits:

  • Chamfer router bits - Chamfer bits cut angles and shapes in the edge of materials. This is a great bit for the handyman wishing to create decorative pieces or edging.
  • Edge-forming router bits - For those with an especially skilled hand, edge-forming bits help with intricate edging tasks.
  • Flush trim router -- This type of bit has a giveaway name. They are used to make the edge of one material flush with another, like trim.
  • Joinery bits - These bits can be found in just about any shape and size, making them perfect for joining two separate materials together.
  • Rabbeting router bits -- Rabbeting bits can be purchased in sets. They're most commonly used to notch the edge of your building supplies. They cut vertically and horizontally at the same time.
  • Raised panel bits are most often used on door panels. They go hand in hand with stile and rail bits.
  • Stile and rail bits - These bits are great for projects involving framework or panel doors.
  • Straight router bits -- These bits are a must have for anyone with a router. These common bits are used for straight down cuts or to form grooves or dados.

Having the bits listed above will allow you to accomplish almost any job, but you may want to check with a professional or expert before getting into a project. Your local supplier will be able to help you chose the best router for the job. And even if you have to go it alone, be sure the check out the packaging. There are usually pictures that will show you the shape it makes.

Read on to find out about differences in router bit shank diameters.

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Router Bit Shank Diameter

If you're new to the world of router bits, you need to know the tool's basic composition. Most router bits are made up of three to four simple components. All bits have a shank, a body and a tip. In the simplest of terms, the tip makes the cut, the body gives it shape, and the shank makes it all possible by connecting the bit to the router. Some bits also have a ball bearing pilot to help in guiding cuts.

The shank of a router bit slides into the collet of the router, which is then tightened to fasten the bit in place. As a rule of thumb, when inserting the shank into the collet, push it all the way in and then pull it out 1/8 " before tightening it down. This will help prevent heat transfer from the bit to your router and vice versa. Also make sure to tighten the collet as much as possible. You don't want your bit to move at all while you're using it. Some people mark their router bit after tightening it down. That way they can monitor any movement that may occur.

Shanks come in two different diameters, ¼" and ½". The ½" diameter bits will generally give smoother cuts without as much vibration. They're also less likely to bend or snap. At the end of the day, ½" bits are almost always better, but not always necessary. If you plan on sticking to the basics, ¼" shanks will serve you just fine. In fact, some smaller routers only work with ¼" shanks. However, as you get more serious and your projects get more complicated, you'll need to move up to ½" shanks and a router that supports them.

If you've been to the hardware store and realized that some router bits only come with ¼" shanks, don't worry. Routers that support ½" shanks come with adapters so they can support ¼" shanks as well. Some bits require ¼" shanks because of their small size. A ½" shank would be too big and limit your ability to make a good cut.

Now that you know the difference between ¼" and ½" diameter shanks, let's talk about router bit drill speeds.

Router Bit Drill Speed

Routers come with variable speeds. This is important because certain bits require certain speeds, not only to give you the best possible cut, but also for the sake of safety. Most routers have a range of 8,000 rpm to 24,000 rpm [source: Spielman].

To help give a better understanding of what that means, let's talk about rpm. RPM stands for revolutions per minute -- it's important to keep in mind that this isn't actually a measure of speed. With regards to routers, it is simply a measure of how many times the bit spins around in one minute. The laws of physics tell us that the outside edge of a bit with a large diameter is actually moving much faster than a smaller bit at the same shaft speed. Since this is true, the speed of a router should decrease in proportion to the diameter of the bit being used. In other words, the bigger the bit, the slower the rpm. This prevents vibration created by bits with more mass.

While most bits will come with information providing a maximum free-running speed, there are speeds commonly used according to the size of the bit. Bits 1 inch or less can be run at the max speed of 24,000 rpm. Bits 1 to 2 inches should be run somewhere around 18,000 rpm, while 2- to 2 ½-inch bits operate around 16,000 rpm, and bits 3 inches or bigger at 12,000 rpm or below [source: Router Workshop]. Sticking to these guidelines will help ensure smooth cuts.

Now, the size of the bit isn't the only factor in determining speed. Other elements that come into play include the router's horsepower, the condition and quality of the bit, the material being used, and, very importantly, the feed speed of that material. If the feed speed is too fast you'll get bad vibrations, and if it's too slow you'll burn your material. The speed of the router and the feed speed should be tweaked to make the best possible cuts. This can be accomplished by practicing on a piece of scrap material before making your final cuts.

Read on to find out more about quality router bits.

Quality Router Bits

The quality of a router bit can be the difference between a gre­at woodworking project and a botched one. It doesn't matter how much experience you have -- a bad router bit will give you a bad cut every time, and there's not much you can do about it.

There are two materials that are used to make router bits -- HSS and carbide. Carbide bits are much more expensive, but they can last 20 times longer than HSS. HSS bits tend to become dull quickly. When this happens, you start burning your wood instead of cutting through it smoothly. If you use your router only a couple times a year, you can get away with using HSS bits, but if you plan on using it every day, or even every weekend, you may want to invest in some durable, long lasting carbide bits.

Quality router bits will stay sharp for a long time. Make sure the cutting edge of your bit is fine. It should be smooth to the touch without any chips. Thicker cutters will also allow you to regrind the bit a number of times, greatly extending its life. When buying carbide-tipped bits, be sure to inspect them carefully. If it looks like the carbide is being held on by poor craftsmanship, steer clear. There shouldn't be any nicks or dips in the surface of the bit that aren't meant to be there. The bit should look new. This seems obvious, but look closely -- some bits may have rust on them. It's also important that the surface of the bit is smooth. If it isn't, it'll collect debris over time and slow you down.

To quickly recap, bits should be sharp, smooth and finely ground. A better bit will cause less vibration. Quality bits equal quality cuts and good ones should last you a long time if properly used.

To learn more, visit the links on the following page.

Related HowStuffWorks Articles

Sources

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