Your calculations are correct. A 14 in diameter wheel needs 27.28 rpm to give a blade speed of 100 ft/min.

(Wheel diameter(inches) x PI) /12 = circumference in feet.

Wheel Circumference (Ft) X Revolutions Per Min = Cutting Speed in Ft per Minute.

I checked both my Vertical and Horizontal saws with an Shimpo electronic Speed Meter that will directly measure both revolutions and surface speeds.

Vertical: 20.25 dia. X PI /12 * 18.9 rpm =

**100.2 Ft/min** (Set for 100 ft/min on saw)

Horizontal: 11.375 dia X PI /12 * 46.2 rpm =

**137.58 Ft/min** (Set for 130 ft/min on saw)

Directly measuring blade speed with Shimpo confirmed the speeds.

Did you or someone else replace the motor on your 4x6? If it had a 1725 rpm motor and someone replaced it with a 3450 rpm motor you would double the blade ft/min...