How to Properly Install a Router Bit

Modern plunge router
By AussieLegend (Own work) [Public domain], via Wikimedia Commons

A power router is a remarkably simple tool in design. The cutting bits are attached to the end of the motor spindle, and as the motor spins, so does the cutting bit, at speeds that reach as high as 25,000 or 30,000 revolutions per minute (rpm). But this high speed comes with risks.

To use router bits safely and to get the best results, the router bits need to be installed properly into the router's collet, the piece that grips the cutting bit and keeps it attached to the motor spindle. Improper installation of a router bit can cause excessive oscillation (chatter) and can increase the likelihood that the bits will break when in use.

To install a router bit you will need only one or two wrenches. Some routers have two nuts, so you will want to use two wrenches with a wrench on each nut. Some routers have a spindle lock and you only use a single wrench on the top of the collet.

Installing a Router Bit

Before beginning any routing operation, check your bit to make sure that it is clean, relatively free of pitch, and most of all, sharp. If the bit is dull, chipped, excessively burned or has any other defect, it should be sharpened or replaced before use.

When installing the bit into the collet, the bit should not be completely inserted to the face of the collet for routing. Instead, insert the bit until the shank reaches the bottom of the collet, then ease it back out about 1/8 inch to 1/4 inch before tightening the collet. The reason for allowing this leeway is that the collet will pull the bit down slightly. If it can't do that because the bit is fully seated, it won't be able to grip it firmly and it may work loose. Some bits are also tapered at the top of the shaft, so the collet wouldn't be able to grab it as securely there. It may work its way out during operation.

When the bit is tightened, there should be a minimum of 3/4 inch of the shank gripped in the collet. If your bit's shank is too short to ensure a 3/4 inch grip, then the bit should be replaced.

Tighten the nut well but do not overtighten it. It should be snug but you don't want to force it. Overtightening can lead to stretching the mouth of the spindle and result in an insecure bit. The spindle can't be replaced by itself, so you would need to buy a new router if this happens.

Tips

  • Always wear appropriate safety gear, including safety glasses and hearing protection, whenever you use your router.
  • Be sure to set your router to the proper speed for your router bit. Setting your router to an incorrect speed will not only affect the router's performance but also can cause the bit to break much more easily.
  • Before beginning any routing operation, be certain that you give the router's motor time to come up to full speed for the chosen setting. Beginning to route before the bit is at full speed can give poor results.