40 - Vacuum Clamping System, страница 21
FEATURE PR CROSS SECTION COMBINED THICKNESS OF VACUUM PLATE AND WORKPIECE VACUUM PLATE DETAIL OUTRIGGER NOTE GLUE UP OUTRIGGER FROM TWO _ __ PIECES OF PVVi \ 1/2"PLY. 3V4" #6 x 1V2" Fh WOOPSCREW ® vacuum plate i/„"-DIA. FOAM (5"X5") BACKER ROD note: ALL PIECES ARE MADE FROM Vz'PLY. lower photo on top ofpage 20. Or if you're making multiple work-pieces, you can use the jig for pattern routing, see box below. VACUUM PLATE. Here again, a plywood vacuum plate (H) has a series of grooves that let you change the size of the vacuum area, see drawing above. And as before, the vacuum plate is attached to a plywood base (I). But this time, the air that's drawn out of the vacuum area passes through both the vacuum plate and the base. This requires drilling a hole in each piece for the air to pass through. RUBBER BAND. One thing to be aware of is that air can leak between the base and the vacuum plate. So to create an airtight seal, I used an ordinary rubber band that's sandwiched between the two pieces, see margin. OUTRIGGER. After screwing the vacuum plate to one end of the base, I attached an outrigger (J) to the other end. It prevents the jig from accidentally tipping which could gouge the workpiece. To provide a stable base, the outrigger is 1" thick. (I glued up two pieces of V2" plywood.) But its height (width) depends on the thickness ofthe workpiece. The idea is to size the outrigger so the workpiece lies flat on the router table. To accomplish this, I cut the outrigger to width to match the combined thickness of the vaccum plate and the work-piece, see Cross Section above. BRASS FITTINGS. After the outrigger is screwed to the base, you'll need to provide a way to connect the jig to the air tube from the vacuum system. As with the sanding jig (and Pattern Routin vacuum table) I used a straight hose barb. But this time, it doesn't thread into the hole in the base. To keep the hose from sticking straight up out ofthe jig (which would be a nuisance), I threaded a street elbow into the base. Then I tightened the hose barb in the street elbow. HANDLES. All that's left is to add two handles. They're identical to the handle on the sanding jig. A Slipping an ordinary rubber band between the base of the routing jig and the vacuum plate creates an airtight seal. Ifyou need to rout a number of pieces to the exact same shape, this small-piece jig is ideal for pattern routing as well. The basic idea here is simple. The vacuum plate on the jig is replaced by a plywood template that has a vacuum area on the bottom, see inset. Once the vacuum is applied, the workpiece is held tightly against the template. By running the template against the bearing on a pattern bit, the workpiece is trimmed to the identical shape as the template, see photo above right. To create the vacuum area, you'll the template for the foam. As with the vacuum plate, there's a hole in the template to draw air out of the vacuum area. But this time, I drilled a large W-dia.) hole. This makes it easy to align the holes in the template and the base of the jig. Note: Here again, slip a rubber band between the template and the base need to rout a groove in the bottom of before screwing them together. 40 ShopNotes 21 |
