Holding power

How much holding power is available?
Vacuum cleaners produce a vacuum to about 9% of absolute vacuum. V-Clamps generate a vacuum pressure to 85% of absolute. A vacuum pressure like this means that when you use the full face of the clamp, 150 kg of air is pushing to hold your workpiece.
What about smaller parts?
When smaller pieces are held, less surface area means less holding force. Indeed when using one third of a clamps surface the holding power is reduced by the same amount. So using one third of the face of the clamp, holding force would be about 50kg
What if I am at a higher altitude?
At higher altitudes air pressure is less which means the holding force of a vacuum clamp reduces with altitude.If you intend to work at the summit of Mount Everest (8,854metres, 29,028ft) the holding force will be reduced from 150kg (330lbs) to 50kg force (110lbs)