How does vacuum work for the woodworker?
The answer is simple – atmospheric pressure is applying approximately 15 pounds/sq. in. (psi at sea level) of force in all directions. With the vacuum pump, we remove most of the air from one side of the wood (creating vacuum), thereby the atmosphere pushes the wood from the other side. This push or force is easily calculated by reading the vacuum gauge and multiplying the reading (called vacuum level) by .5. Therefore, if you are applying 26″Hg to 1 sq. ft. of wood, you will generate 1872 lbs. of clamping force. (26 X .5 X 144 sq. in.). This force works to hold wood for machining (routing, sawing, sanding, etc.) or for applying veneer or making built up laminations.
