We RATE Vac-Clamps at 80% of absolute vacuum. That means that they are rated to pull -12.7 psi. They actually produce between 86% to 88% of absolute with a supply pressure of 100 psi. Given the full face surface area of the clamp, this will yeild a theoretical holding force of 330 lbs. Dynamic loads will always derate that holding force, but not by a huge amount.
Being injection moulded the "flatness" is not perfect. To give a broad tolerance +\- 0.25mm (+\-0.01") The way to achieve excellent results is to bolt the clamp down and do a skim cut over the whole face of the clamp. The material is a filled nylon, so it will machine very well.
Base is a filled Nylon (not glass). Durability is the key to this product, we have spcifically made the item to last and to be abuse tolerant. You can make a cut into the face up to 6mm (0.25") deep and the clamp will still work as good as a new item. One of the first prototypes has been in use by a school at least twice a day for the last 3 years. It is still working without fault, and they have not had to replace the seal yet.
Part of the design rationale was to allow chaining of the product to just about any configuration, at any time. You can start with one or two and add to them at any stage if or when the need arises. We have a number of people whom use two or three clamps and supplement stability by using support blocks of the same height. The support blocks will improve quality of cut.
The single sided clamp (VC4) uses about 1CFM. More clamps means more air consumption.
We have a different way of dealing with the through cut issue. A tall seal allows a shim to be put in between the workpiece and the clamp. This raises the workpiece off the face of the clamp to allow the through cut. The seal can be placed anywhere that the seal channel will allow.
The Vac-Clamp website
http://www.vac-clamp.com has a list of distributors.
We have not done a noise test on the product, so I cannot give a difinitive answer on this. An air dusting gun/blower is noisier.
Errol Weber
Vac-Clamp