You need to know the control type, Because many routers are Universal motor type (AC/DC) the controller may be triac phase angle control, if so you cannot use on a PM DC motor, but there are many out there, (All Made by one Manuf,) Baldor and others that are full-wave SCR control and you can use these, and pick them up for ~$100.00 new, or $20~$25.00 on ebay.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.