The General Rule of Thumb on Speed
While it can take some experimentation to get the speeds exactly right, the general rule of thumb is, “the larger the bit, the slower the speed.” 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 just 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.
Mount the Bit Correctly
Additionally, always be certain to mount the bit correctly in the tool. Make sure 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 routing freehand when shaping with large-profile bits. It is much safer to use large profile bits in a router table at the appropriate speeds.
