How to use carbide router bits

long plunge bitIf you've ever broken a bit, you've probably wanted to know how to use router bits without breaking them. Carbide can snap from vibration and bouncy chattering. Some damage may be inevitable, but the first defense starts by using a shorter length whenever possible. Use a bit just as long as needed and no longer. If it flexes while pushing too hard, the stress can result in chipped carbide. Steel can flex and return to shape, but aggressively routing dense hardwood can crack brittle carbide or compromise its attachment.

Narrow, long bits are prone to chipping and breaking, and typically come minus the benefit of guarantee. For example, this straight plunge bit with a half inch shank, a 1/2 inch cutting dia., and a 2 in. long flute is likely to flex.

On a 1/4 inch shank with a 1/4 in. cutting dia., even a 1/2 in. one risks cracking. If you need extended length, use a wider one that has a better chance of avoiding damage from flexing. A shank size of 1/4 inch is quite flexible. A fatter one is stiffer and won't break as easily.

If you notice a wobble or noisy buzz, stop. Locate the source of vibration and reduce it to a calm hum. Stabilize the work. In hard materials, go easy instead of rushing. The harder you are routing, the more the binder could break down. Routing by consistently sweeping one way is wiser than abruptly churning back and forth in choppy, unpredictable jerks. As the grip is tested by the strain of such usage, it might slip. Impact can crack carbide. Try to avoid hitting knots or embedded metal fragments.

Ball bearing bits

router bit bearingA ball bearing guide limits the depth of cut by rolling along a template. It is a separate part, most often installed at the end. It must roll independently. It may extend on top or be found below the flutes, which are the sharp parts of a router bit. Once firmly pressed in, the pilot engages the stock. It should not turn with the bit; that defeats its purpose. Roll it to feel for any hesitation. If the assembly is so dirty it won't roll, it will smudge or singe the surface.

Clean the bearing by simply flicking or brushing away the clumps of pitch so it won't bounce or leave a repeating pattern on the wood. Normally it does not need any additional lubricant. If you are cleaning bits in fairly new condition, you do not want to let solvent strip out the grease in the ball bearings. To loosen a stiff bearing, squirt on one miserly drop of WD-40, work it back and forth and then wipe it all off thoroughly. When a stuck bearing is stubbornly frozen or rusted, the internal lubricant is dried up. If it is hopelessly bad, you might let WD-40 penetrate the seized parts, and wish for a partial loosening. That is only a temporary fix in desperation to get a job done. If it works, it probably could have been fixed by a toothbrush and elbow grease alone.

In a worst case scenario, to disassemble and then replace a bearing by another one of the same size is still less trouble than obtaining a whole new bit. Installing bit bearings is not really a chore if they have good cap screws that aren't damaged. Remove an end bearing by using an Allen wrench to unscrew its cap. If the head of a screw is too damaged, vise grips could probably still take it off. To remove an upper, shank mounted one, unscrew the set screw on the retaining collar. Then slide the parts together off the shaft. Keep all the small parts on a towel so they don't get lost before you can assemble them again.

After a flush trim bit is reground several times, it may get smaller than the guide. While trimming laminates, it might leave unwanted ridges. You could file off the excess plastic laminate, or save yourself the effort by simply replacing a bearing by a new, smaller .492 inch one.

Delrin or white nylon bearings are slightly softer to avoid marring solid surface or plastic. They have a few specialized uses; primarily for routing sink bowls.

A solid carbide flush trim bit also cuts on the side, and is guided along the stock, but it just has a simple static pilot which is a short smooth section near the tip.

Homemade storage box

A storage case protects bits from rattling around and getting broken. You can use free recycled materials to assemble a simple but effective homemade box. It is as easy as fitting a block of Styrofoam in a shoe box. Poke each shaft into it. Space them apart so none touch. Toss in a packet of silica gel to discourage rust. For straight bits, you can craft some caps out of a plastic tube cut in short pieces.

For storing or shipping, you can warm up some soy plastic to dip the heads. When you are ready to route, cut the seal just behind the carbide and carefully slip it off. Wipe off the thin film of oil with alcohol before using it.

Router FAQ

Frequently asked questions on how to use a wood router are answered in these guides. Find tips on using router bits and explore their various uses. Learn tricks for getting more out of them, improving their performance, and troubleshooting typical routing issues.