The chart at the bottom of this page provides a guideline as to the maximum speed that should be used for particular diameter bits. However, this chart is a general guideline. Consult your router's user guide or the documentation that accompanied your particular bit for specific details on setting the appropriate speed for the bit.
Additionally, always be certain to insert the shank completely into the collet, then pull the bit out slightly to avoid bottoming out the bit in the collet.
Also, avoid free-handing with large profile bits. It is much safer to use large profile bits in a router table at the appropriate speeds.
Router Bit Speeds
|Bit Diameter||Maximum Speed|
|Up to 1 inch||24,000 rpm|
|1 to 2 inches||18,000 rpm|
|2 to 2-1/2 inches||16,000 rpm|
|2-1/2 to 3-1/2 inches||12,000 rpm|