JoeWoodworker Veneer
The Official Website of this Non-Professional Woodworker ™

Part 1

Veneering Basics

14 Good Reasons
Vacuum Press Uses
Vacuum Press Options

Questions & Answers
Part 2a (Option 1 of 2)
Project: V2 Venturi Press

About Project: V2
Parts List
Build the Manifold
Build the Reservoirs
Assemble the Venturi
Make the Carrier
Wire the Press
Testing and Adjusting
Mods and Options
Part 2b (Option 2 of 2)
Project: EVS Pump Press

About Project: EVS
Parts List
Pump Selection
Build the Manifold
Build the Sub-Manifold
Build the Reservoirs
Make the Carrier
Final Assembly
Wire the Press
Testing and Adjusting
Mods and Options
Part 3
Vacuum Bagging

Vacuum Bag Basics
Polyurethane vs. Vinyl
DIY Vacuum Bags (A)
DIY Vacuum Bags (B)
Connect the Bag
Bag Closures
Breather Mesh
DIY Frame Press

Part 4
Veneer Information

About Veneer
Veneering Myths
Backer Veneer

Veneer Glues
Veneering Tips
Substrate Materials
Flattening Veneers
A Sharp Veneer Saw
Jointing Veneers
Taping Veneers
Dealing with Defects
Curing Glued Panels
Veneering w/o Vacuum
Hammer Veneering
Iron-On Veneering
Veneer Storage
Amazing Bookmatches
Copper Veneer Guide
Paperbacked Veneer

Edgebanding Guide

Part 5
Miscellaneous Info

Vacuum Forming
Vacuum Chucking
Vacuum Clamping
Vacuum Clamp Matrix
Vacuum Infusing
DIY Vacuum Manifold
JWW Visitors' Vacs
Veneer Quality
Veneering FAQ
Veneer Glue FAQ
The Vac FAQ
Copper Veneer FAQ
Downloads (PDF's)

Vacuum Veneering - Tips, Tricks, and More

Project: E-Vac Pump Driven System
Selecting A Vacuum Pump

Speed and Maximum Pressure
Vacuum pumps are often rated on the flow capacity which is stated as CFM (cubic feet per minute). It references the speed at which the pump is capable of moving or removing air and is most often measured at zero pressure. A pump rated at 1 CFM will be fine for flat panel work on vacuum bags up to 4' x 4'. For bags up to 4' x 8' a 3 CFM or greater pump is needed.

If your vacuum press will be pulling down curved veneer forms or bent laminations, the general rule of thumb is that the pump must be three times faster. This means that a 3 CFM or greater pump is best for vacuum bags up to 4' x 4' for this type of use. Why? Because there is, on average, 3 times more free air inside of a bag containing a bent lamination than there is inside a bag containing a flat panel.

Vacuum pumps are also rated by their maximum achievable vacuum at sea level which is often expressed as inches of mercury or "Hg". For vacuum veneering, the minimum acceptable level of vacuum is 18". The ideal vacuum level though is 21" of Hg. At the high end, the maximum level of vacuum for veneer work is 25.5" of Hg. Anything over this amount is not only overkill, it's also harder on the pump and once in a while, extreme vacuum levels can cause the veneer to develop small pustules of glue on the veneer face.

Type of Vacuum Pumps
The next consideration when building a pump based vacuum press system is the pump style. Here are the some of the options:

  • Diaphragm pumps are very quiet and durable. This type of pump is oil-less and usually has a small footprint. They are ideal pumps for a vacuum system. Typical CFM rating is 1 to 3.
Gast Diaphragm Vacuum Pump
  • Piston pumps are not as quiet as diaphragm pumps, but are just as durable. They are almost always oil-less and also work well for a vacuum press. Typical range of CFM is 2 to 5.
Thomas Piston Vacuum Pump
  • Oil bath pumps are less noisy than piston pumps but not as quiet as diaphragm pumps. This type of pump has a tendency to emit a plume of oil into the air. For most users, this can be a huge issue that causes problems with the finish that is applied to the veneered project or any other unfinished project in the vicinity of the pump. This type of pump requires occasional oil changes and can draw a large amount of amperage. Usually, these pumps range from 3 to 6 CFM.
Robinaire Vacuum Pump
  • Rotary vane pumps are available in oil-less and lubricated styles. They are generally maintenance free but they get very hot during use. This can create a serious issue if the thermal protection circuit kicks on while your press is in use. It's a good idea to have a standby unit on hand in the event that the rotary vane pump overheats. Typical CFM range for this style of pump is from 5 to 20. If you choose this style pump, you may need a relay to do the high current switching for the vacum controller. These pumps are notoriously difficult to adapt to vacuum press use due to electrical issues.
Gast Rotary Vane Vacuum Pump
  • Refrigerant compressors can also be used for limited runs of vacuum press work. They are quiet, but slow to pull a full vacuum. Typical CFM is less than 1.
Refrigerant Compressor

Vacuum Pump Manufacturers
The most common names in vacuum pump apparatus are Gast Manufacturing and Rietschle Thomas (pronounced 'rich-ley thomas'). Both companies offer very refined pumps in a wide range of models.
Other manufacturers include Alcatel, Edwards, Sargent, Welch, Busch and Leybold. These particular manufacturers offer high end, industrial, or scientific-use vacuum pumps.

Restart Pressure
The next consideration is for a pump based vacuum source is "restart" pressure. Many smaller pumps have a zero pressure restart rating. This means that if you turn off the vacuum pump and turn it on again without relieving the back pressure, the pump will not start. Some rotary vane vacuum pumps and refrigerant compressors can restart regardless of the pressure in the system. The good news is that there is a simple fix that will allow any vacuum pump to work in a cycling mode. There's more about that on the next page.

Testing Your Vacuum Pump's Restart Pressure

1. Plug up the air intake on the pump (I use my finger).
2. Turn the pump on for a few seconds to let it build up full pressure.
3. Turn the pump off and then turn it on again.

Did it restart without hesitation?
If it did, you won't need to unload the vacuum using a sub-reservoir and Mac valve as described on the next page.

Yes, Joe is a practicing Catholic
The Vac FAQ
Heat Lock Veneer Glue