Quick Question about Vacuum Presses

[banditto1969]

That I couldn't find the answer for with the search or on joewoodworking...

I am to make a pair of bookshelf speakers and am nearing the veneering portion. I decided to use a vacuum press being I am going to go with highly figured burly maple. The glue is Better Bond brand and the veneer has been flattened.

So my idea is to do one side at a time and put it in the press for 5-6 hours each side. I am using a vacuum pump at work which goes to -15inHG, is that low enough? Also should I have to keep the pump running the entire time? I used a check valve but it still seems to leak over time.

Oh and will applying a finish later soften up the Better Bond and make the veneer bubble?

Thanks in advance!

[jbateman]

15in is marginal.
Don't rely on the plastic bag to press the veneer down to the substrate...use a flat board, like melamine coated particle board, as a caul, to press on the veneer. Make it slightly oversized, and round the corners so it doesn't puncture the bag. (assuming your not making a curved box)

If the bag or valve leaks, you need to keep the pump running.
And it only needs about an hour in the press...not 6.
Solvents won't affect the glue once it's cured.

[banditto1969]

sweet thanks

[AlanH]

I am using a vacuum pump at work which goes to -15inHG, is that low enough? Also should I have to keep the pump running the entire time? I used a check valve but it still seems to leak over time.

Double check your gauge. Many gauges have a double scale in both psig (i.e., psi gauge) and inches of mercury. If the pump only gets to -15 inHg (i.e., -7 psig) there is either a leak in the system or it is in serious need of a rebuild.

[banditto1969]

Well it most likely is factory set to -15inHG, it's from a soot particulate meter used in diesel testing. I may have others back in storage but haven't looked. I figured the vacuum pump I had laying out would do the job being it is the size of a large microwave oven.