Hegner 18" Scroll Saw and Vacuum Press

The saw pictured here is secured to a wood base consisting of two pieces of one-inch stock joined on one edge by a piano hinge. The wood base can be raised or lowered to match the cutting angle and provide a level saw table. For cutting at an angle, Hegner uses a tilting table as opposed to tilting saw arm. For marquetry work, for which the saw is primarily used, the table would be tilted 13 to 14 degrees to the left, as shown, and brought level by use of the adjustable wood base for ease of cutting.

A vacuum press is used to secure the picture to the substrate of plywood or particle board. A vacuum press may not produce as much pressure as other methods of clamping, but its pressure is more than adequate for marquetry purposes and by its nature ensures that each piece of the picture receives the same amount of pressure. Various clamping devices or weights can also be used successfully, but nothing compares with the uniformity of the pressure exerted by a vacuum press.

Shown above is the used freezer rotary compressor, which cost less than $50. The black vacuum line attaches to the vacuum bag and enclosed board, shown below. The vacuum gauge was purchased at an auto parts store and measures the vacuum in Hg or inches of mercury. The gas/water valve was purchased at Lowes. The valve was installed in the line to maintain the desired level of pressure by allowing air into the line.

The exhaust line posed the only real problem in setting up the press. The exhaust air contains tiny amounts of oil, which was not a problem in a shop but is most unwelcome in a carpeted room. I tried extending the line but the oil was always present. The problem was finally solved by running the tubing into a jar containing about an inch of water, and inserting a second small piece of tubing to exhaust the air. On the underside of the lid, a small sponge was glued to absorb any water or oil particles circulating in the jar. The jar with tubing and sponge can be seen in the photo below, alongside the On-Off switch:

The vacuum line attaches to a 1/4-inch brass barb on the underside of the board which is inside the bag. The bag (a fisherman's tournament Bass Bag, which I am told can be purchased at most tackle shops) measures 26 x 34 inches and the board inside the bag measures 16 x 20 inches, shown below:

The top side of the bag and board can be seen in the picture below. The lines defining the 4-inch squares were made by a circular saw blade, with a 1/8-inch kerf, set to a depth of 3/16-inch. The blue metal disc is taped just above the vacuum fitting so that the bag is not sucked down, reducing the suction. After a picture is placed inside the bag for pressing, about 6 inches of the bag can be folded into itself so that the bag will in effect seal itself after an initial hold-down.

Finally, the pressures obtainable are shown below. When the system is tight and no leaks can be heard, the maximum Hg is about 27.5 or 1,945 psf or 13.5 psi.

NOTE: The reader might be interested in reviewing another approach to construction of a vacuum press which, although for an entirely different use, i.e., building model RC Electric Helicopters, is equally applicable for use by the marquetarian. (The jar with tubing and sponge, referred to above, was the suggestion of a member of that organization.) Be sure to visit Dream Models, originating in Ghent, Belgium, for more information.

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