The speed at which you use your carbide bur in your rotary tool will depend on the material you're using it on and the contour being produced but it's safe to say you do not need to exceed speeds of 35,000 RPM. The table below shows some approximate speeds.
Diameter of Burr RPM
2.35mm or 3/32" 17,000 - 26,000
3mm or 1/8" 17,000 - 26,000
6mm or 1/4" 11,000 - 16,500
12mm or 1/2" 8,000 - 12,000
16mm or 5/8" 7,650 - 11,500
2. Apply only a little pressure
As with all drill bits and burrs, let the burr do the work and apply only a little pressure otherwise the cutting edges of the flutes will chip away or become smooth too quickly, reducing the life of your burr.
3. Keep The Carbide Burr On The Move
When using your carbide burr try not to keep it still for too long as this will prevent the burr from digging and jabbing into your material causing unsightly marks and roughness.