Tools

I'd done a bit of work with veneer on small projects using curved or flat cauls and clamps. A small cabinet job, where a single sheet of figured veneer plywood would have cost me more than $400, motivated me to build my first flip-top vacuum press.

My design is an upside down version of Joe's frame press with a few changes/additions inspired by the commercial flip-top frame presses, VacuPress in particular. I liked Joe's idea of using the table saw out-feed table, but using the end of my main workbench gave me a place to work (spread glue, etc) and more design options.

I liked the VacuPress grooved platen/caul - with the vacuum port in the middle - that the frame seals against. I decided on a 5/8" MDF platen that could be clamped to my workbench if necessary. I wanted the biggest press I could make with Joe's 54" x 36" 20mil Polyurethane (...now VS Elite, was Dura-Max) and I wanted it fairly easy to move/store.


The bottom of the platen has 1x1's along three edges that register the press to the workbench. Turn buttons could be mounted to the 1x1's to clamp the frame to the workbench. The 1x1 on the end is also used to mount hinges to the frame. The top of the platen has grid and perimeter grooves that are 1/4" wide (1/8" is better) x ~3/16" deep. To cut the groves I used a router guide bushing and 1/4" MDF scraps. I drilled a hole at the center intersection and routed a pocket on the bottom of the platen for a connector fitting mounted to a 3/16" aluminum plate. I over complicated the mounting/seal and would use something like polyurethane caulk and 1/2" coarse thread wood screws next time. I routed a ~1/2 x 1" hole in my workbench for one of Joe's connectors.

I also liked the VacuPress method of mounting the membrane to the frame (and sealing it to the platen). Any material that doesn't follow a straight path is easier to secure. Instead of sandwiching the membrane between two strips of wood I clamped it between 1x1's that fit in a ~3/16" deep dado on the frame. The dado is centered in the ~1x3 frame stock and sized so that the 1x1's plus the membrane are a snug fit. I started with a 3/4" dado using a router table and moved the fence back (taking a pass on each edge to keep the dado centered) until I got the fit I wanted. I eased the edges of all the frame parts with 1/16" and 5/64" radius round over bits, i.e. pretty small - hand sanding them would be fine. I drilled countersunk pilot holes (96mm/3-3/4" on center, up to 6" would probably be OK) in the frame (full depth on the face, 1/3 depth on the back side to compensate for any puckering of the 1x1's and membrane by the screws) and used 1-1/8" auger point screws to mount the membrane/1x1's. I sized the frame so that there would be a small gap between the 1x1's and the platen.

There are three benefits to mounting the 1x1's on the bottom of the frame. First, the 1x1's frame the platen and limit how much the frame can flex under vacuum. The width/lateral stiffness of the fame is less important. The second benefit is a simplified perimeter seal. Instead of membrane-wood-foam-platen, it's membrane-foam-platen. The frame material doesn't matter because it's no longer exposed to vacuum. The third gain is that the foam seal is tucked out of the way where it is less likely to get damaged. This is particularly important with this method because the tape doesn't stick real well to the membrane. I used denatured alcohol to clean the membrane before mounting the tape and so far so good (...acetone works better. A strip of laminate against the wood will protect the finish) . A side benefit is that the platen and 1x1's (temporarily mounted with a few screws) can help with assembling the frame corner joints. I used splined miters and four bar clamps tightened/loosened to align/tighten the joints (I glued them 2 at a time).

I sealed the MDF edges and groves with OneTime and finished the frame and platen with KEM Aqua (waterbased lacquer). I use a Thomas vacuum pump with a vacuum gage, a filter and a bleeder between it and the press (continuous run). I have no idea how airtight my setup is, but evacuation takes seconds and the gage reads 25"HG with the bleeder closed.

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