What do woodworkers need to know about vacuum pressing and syrface applications? Here are 5 of the most frequently asked questions:

1: What is vacuum clamping?

A: The ability to hold a workpiece with up to 1800 lbs/square foot of clamping force. The holding force is on one side only and does not introduce physical obstructions on the edges or other side.

2: What kind of glue should I use in a vacuum press?

A: There are many types of glues on the market and which type you use with a bag press will depend on your needs. In general, a vacuum bag does not care which glue is used, it will press all glues with 1800 pounds per square foot of pressure. There are two concerns regarding gluing in a bag that you should be aware of.

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3: How long does it take for the glue to dry?

A: Drying time normally depends on several factors: type of glue — generally, the more open time the glue allows, the longer the set time; temperature of the shop — the warmer the shop, the faster the set time; substrate material — with typical water-based glues, the water will be absorbed into MDF, particleboard, etc., faster than a solid wood like oak, therefore, the drying time is shorter.

4: Vacuum clamping: should I keep it turned on?

A: In virtually all cases, the vacuum pump is always kept on when vacuum clamping. The reason for this is safety. Take a common vacuum clamping application like template routing. Most woods or wood products are porous; therefore, they leak or don’t hold vacuum.

Shutting the pump off at a high vacuum level will only mean it will cycle on and off. However, this is not the big concern, the major issue is will the pump come on and pull enough vacuum before the work piece breaks loose. The routing process puts lateral stress on the work piece. A drop in holding force could be enough for the piece to break loose before the pump starts and regenerates enough vacuum level to hold the piece securely in place.

Q: What are pump capacities and how they are defined?

A: Vacuum pumps are usually defined by two parameters; vacuum level and vacuum flow. A third parameter not often discussed in the woodworking industry is the time to evacuate a given volume (usually 1 cubic foot) a given vacuum level.

Source: Quality VAKuum Products. For more information, call (800) 547-5484 or visit QualityVak.com.