I understand shapers top out at about 10,000 rpm while routers will have the range of 10,000 - 22,000rpm. Much is said about the need to achieve adequate tip speed to get a satisfactory cut often putting routers as tool of choice for small diameter bits. Is not feed rate just as important as tip speed for getting quality cuts? Would a small diameter router bit at 10,000 rpm and some slow feed rate produce an equal quality cut to the same bit being use in a higher speed router at any feed rate?
-Joe
Colorado Springs, CO
Our Expert
As a rule-of-thumb, router bits should spin much faster than shaper cutters because the diameter of the average router bit is much smaller; the extra RPM is needed to increase the rim speed and create enough cuts-per-inch to create a smooth surface that's free of a "washboard" texture.
But another reason that routers run faster than shapers is that they need the higher RPM's to compensate for their lack of torque. Universal motors, such as those used in routers, lack the torque of induction motors which are used in shapers and other stationary power tools. So they spin faster to make up for it.
However, you're right in that you can dramatically reduce the feed rate and use a router bit in a shaper and achieve acceptable results. I know because I have often run router bits in a shaper with good results simply by reducing the feed rate. Keep in mind that while this method works for small profile bits, such as an ogee or roundover, it will not work as well with very small diameter straight bits or straight bits with just one flute.
