The Clamp in Use
Vacuum Bridge Clamp in the foreground. The fixture has been connected to the LMI Vacuum Pump by inserting the pump's hose into the Pisco connector at the end of the bridge clamp fixture. The hose is merely pushed into the connector - it locks in place. The hose is released from the connector by pushing in the white ring on the connector and pulling the hose free.
The vacuum pump and Vacuum Bridge Clamp are ready for use. The guitar top and the bridge bottom are leveled and prepared for gluing. The plastic bridge pins will be used to pin this bridge in place during gluing. There are a variety of ways to pin the bridge in its exact location, this is a simple one that can be used when re-gluing a bridge that was originally in the correct location for accurate intonation.
The bridge has been glued and placed into position. The top of the bridge pins have been clipped off so they won't protrude above the bridge during clamping.
The clipped bridge pins have been pushed into the outside string holes and the bridge is now secure from movement during clamping.
Tape has been placed over the bridge pin holes to seal the vacuum during clamping. Without sealing these holes into the guitar body the vacuum clamp will never create vacuum pressure. This hole sealing process is not needed when a bridge is attached to a new guitar.
With the bridge fitted, glued, and pinned in place the clamping will begin. Carefully place the Vacuum Bridge Clamp over the bridge as shown here with the bridge about in the middle of the fixture.
Turn the vacuum pump "on". Gently press down around edges of the clamping fixture - maybe using both hands - to create a solid seal with the top all around the fixture. With this repair we are clamping the bridge down with the pick guard attached and the pick guard is under one corner of the fixture. The foam rubber seal on the bottom of the fixture must be pressed down tight around the pick guard before the clamp will create vacuum pressure and begin pressing down on the bridge. The moment that a good seal to the top is created the vacuum will begin and will suck the rubber membrane down over the bridge as shown in the photo.
Glue Clean up - After about 10 to 15 minutes of vacuum pressure on the bridge, turn the pump "off" and carefully remove the clamping fixture from the guitar top. By this time the glue squeezed out along the edge of the bridge is beginning to harden and this is the best time to clean it away. This glue cleaning should be done quickly with a damp cloth and soft probes - DO NOT use an abundance of water. At this stage excess water can dilute the glue under the bridge. With the visible glue removed, place the vacuum bridge clamp fixture back on the top over the bridge and turn the vacuum pump "on". Press the clamp frame down around the edges until vacuum pressure is once again clamping the bridge to the top, as in the photo.
Clamping Time - It is best at this stage to continue the vacuum clamping pressure at least 45 to 60 minutes - longer if you like. Most water soluble glues will have firmly tacked and set enough by this time to allow clamp removal without harm to the joint. Of course, it is best to let it cure more fully overnight before any other procedures on the bridge or instrument.
The Vacuum Bridge Clamp is removed from the bridge and locating pins are removed. The bridge is firmly glued to the top.
A 1/2" foam rubber gasket is glued to the bottom surface of the frame to conform to the top and produce an air tight seal for clamping. The flexible, yet firm, foam rubber gasket can even form an air tight seal when a portion of the clamp is placed over a pick guard or the top is very arched. And of course, the foam bottom gasket does not mark or harm the top or finish.
The clamping fixture is designed to pull vacuum in the area between the membrane and the guitar top surface under the membrane. There is a vacuum outlet in the frame below the rubber membrane and this air outlet hole is connected to a Pisco quick connector on the outside of the fixture. The fixture is connected to the vacuum pump by 1/4" hose attached to this connector.
In operation, air is pulled from under the rubber membrane by the vacuum pump and the vacuum created sucks the membrane down to the guitar top surface at a pressure of 14 pounds/square inch - atmospheric pressure at sea level. That's 98 pounds of clamping pressure on an average bridge - about 7 square inches of surface. That's enough to glue it well.
The Vacuum Bridge Clamp - SPVACPB works well with our Vacuum Pump - SPVP and will be demonstrated here using this pump. There is no additional preparation of the Vacuum Bridge Clamp as it comes to you. Our only preparation here is setting up the vacuum pump and connecting it to the clamp with our vacuum hose.
These instructions are not intended to demonstrate the complete bridge gluing process but rather to show how this tool is used in the clamping portion of this process. All other steps - preparation of the top and bridge surfaces, locating the bridge accurately, pinning the bridge in place, glue clean up, etc. - are the same as for gluing a bridge down with ordinary deep-throat clamps. We are assuming that there is already bridge gluing experience and the entire bridge gluing process should be familiar already.
This vacuum clamp can be used to re-glue a bridge in a repair situation or to clamp down a new bridge during construction. We are demonstrating here the use of this clamp in a repair situation, re-gluing a bridge onto a Martin 00-21. The clamping procedure is the same for attaching a bridge to a guitar in construction.