Assembly Detail

Beam side

Attachment block

Air supply port




Air supply port

Air supply port

I. After boring the air supply port, rout ^"-wide, '//-deep grooves bisecting the port and paralleling the platen's edges.

grooves in it. covering the grooves with plastic laminate, then riddling the laminate with holes. You have to be asking yourself, does something this simple really work?

1. Cut the platen blank. As I said, the platen is a piece of v'4-inch plywood. To work properly, the platen must be dead flat, so select your plywood carefully. Cut it to the dimensions specified by the Cutting List.

2. Bore the air supply port. The air is supplied by your shop vacuum. For the air to get into the passages that you will be routing into the platen in the next step, you have to boa- a hole in the platen that's big enough for the shop vac's hose. Because the connector can extend only % inch into die platen, it's important that the port closely match the connector's diameter.

Begin by determining how big the hole must be. Measure the outside diameter of the connector on the hose with a pair of calipers. Bore a test hole with a Forstner or multi-spur bit as dose as possible to the measured size of the connector. A large hose might require that you use a hole saw.

If the hole is slightly too small, you can file it larger with a half-round rasp. If it's too large, you can wrap tape

3. Lay out the air holes on the plastic laminate, arranging them on a I" grid. Drill the holes with a Yn" bit. Apply the plastic laminate to the platen so the holes line up over the grooves.

around the end of the connector. The hose must fit rea sonahly air-tight.

After you've decided on the bit you'll use, lay out the 1 center of the air supply port, following the drawing Platen Detail. Then bore the port. You can bore completely through the platen.

3. Lay out and rout the air passages. The air is dispersed across the platen through a grid of grooves routed j into the platen's bottom.'Fhc drawing Platen Detail shows these air passages. Note that diere is a S-inch-wide x '/2-inch-deep perimeter groove and a similarly sized one extending from side to side through the air supply port. ! Completing the grid arc a dozen Vinch-wide x Vinch-deep grooves routed from end to end. None of diese grooves, of j course, breaks through the edge of the platen.

How you produce the grooves may have a bearing on J how you lay them out. It is useful, later on, to know where the grooves are, so you do want mark the groove centerlincs on the platen edges. Rout the grooves with a plunge router equipped with an edge guide, or on the router table.

Rout the large air columns first. Use a H-inch straight J bit.Adjust the depth stop for a '¿-inch-deep cut. Set the edge j guide so the centerUnc of the cut is 1 inch from the stock's edge. Rout the perimeter air passage. Don't forget that these

Use a hand held router with an edge guide to cut the air-passage grooves. Set the edge guide to rout the perimeter grooves first. Don't fuss with stop blocks; just lay out the inside corners of these grooves, then rout from mark to mark. To start the cut, tip the router so the bit is clear of the work, as shown here. Then begin advancing the router as you lower it into the work (here lam pulling the router toward me).

grooves stop short of the edges of the stock. You'll find it easiest to rout these grooves in three or more passes of increasing depth.

Reset the edge guide, and rout the air passage that bisects the air supply port. Rout across the width of the platen, from the perimeter groove along one side to the one along the other side.

Now rout the small air columns. Switch to a ¿6-inch straight bit. and reset the depth stop to produce a 56-inch-deep cut. Set the edge guide position to rout the two grooves closest to the platen edges.What you do is rout two grooves, one referencing each edge of the platcn.Then reset the edge guide and rout two more grooves. Keep resetting and routing until all the grooves have been cut.

Just remember: DON'T break through the edges. You want air escaping only through the tiny holes you will be drilling through the plastic laminate you will be applying.

4. Apply the plastic laminate to the platen's top. As 1 mentioned, the platen must be flat to work, and if you cover only the bottom surface with laminate, the platen is almost certain to cup. So cut two pieces of laminate to the dimensions specified by the Cutting List, holding one for the next step.

Apply contact cement to the laminate and to the top of the platen. When the cement is dry, apply the laminate to the platen. With a router and flush-trimming bit, trim the laminate overhang. Drill a hole through the laminate covering the air supply port, and insert the bit through the hole so you can open up the port. Switch to a chamfering bit and make another pass around the perimeter of the platen, eliminating the sharp laminate edge.

5- Drill the air holes in the plastic laminate. The many holes in the platen's plastic laminate bottom must be drilled before it is applied. If you drill them alter it is applied, all the dust and chips created will collect in the air passages, and they may restrict air flow.

Now 1 know the usual approach to laminate work is to cut the laminate oversized and apply it to the substrate with some overhang around all four edges. In this case, simply plan to align one edge of the laminate flush to the substrate edge, and have the overhang only on the other three edges. Cut the plastic laminate to the dimensions specified by the Cutting List. These dimensions provide leeway for you to trim it flush after it is cemented in place.

Given the application approach, you simply have to lay out the holes, working from the "flush "edge. As the drawing Platen Detail shows, the air holes are drilled on a grid of 1-inch squares. Find the center midpoint along the flush edge, and lay out the grid from that point. L'se a pencil and a framing square to extend lines across the laminate. Then turn the laminate 90 degrees and pencil lines from side to side, forming a grid with 1-inch squares. At each grid intersection, you must drill a hole through the laminate.

Back up the laminate with a clean, solid piece of scrap—plywood or medium-density fiberboard. Drill the holes using a v52-inch twist-drill bit in a portable drill. The holes don't need to be located with absolute precision. It isn't hard, just tedious.

6. Apply the plastic laminate to the bottom.

Despite the grooved substrate and the perforated laminate, this is really a straightforward job. Set up first. Clamp a straightedge that's thicker than the platen to the workbench l>etween you and the platen. Pull the platen tight against it. and mark the center of one or two air passages on the top of the fence. You are going to use these marks to align the laminate, and you are going to align the laminate's "flush" edge with this fence, so make sure you have the platen oriented appropriately.

Now apply the contact cement. As you spread it on the grooved platen, try to avoid getting too much clown in the grooves where it might obstruct the flow of air. This isn't difficult. What is tricky is applying the cement to the laminate. You have to kind of paint stripes of the cement between the holes. You don't want a film of cement gumming up the air holes. I found that a disposable bristle brush worked just fine for applying the cement in this particular situation. Allow the cement to dry sufficiently.

Now apply the laminate to the platen. Stand its flush edge on the platen, tight against the fence, and make sure the appropriate strings of air holes are aligned with your alignment marks on the fence. Flex the laminate so it bows, and gradually lay it onto the pL'Ucn. Burnish it down with a J-roller or the heel of your hand.

Set up your laminate trimmer or router with a flush-

Advance planning is the key to successfully laminating the platen. The grid of air holes must be laid out from a "flush" edge, then drilled through the laminate. The edge of the platen corresponding to the "flush" edge of the laminate must be butted against a fence. Alignment marks must be scribed on the fence and the laminate (on the masking tape). The laminate can then be "rolled" down onto the platen, as shown, with the laminate's air holes aligned over the platen's air passages.

trimming bit. and trim the laminate edges flush with the platen edges. Switch bits and rout a narrow bevel around the edges to finish off the job.

7. Take a test drive with your platen. This is a deviation from proper step-by-step decorum, I admit. But this is so cool you need to try it out right away. And now that you have the air holes drilled, you can get it afloat on a cushion of air.

So stick one end of the hose in the shop vac's exhaust port, the other in the air supply port on the platen. Turn on the vac and see how nicely the platen floats. Pile some tools on it, and see how it reacts. Call the family together and show it off. It's a great trick.

Okay, break's over. Back to work.

8. Make and install the attachment block. Cut the block to the dimensions specified by the Cutting List.

I .ay out the hole for the mounting rod. Note, in the drawing Column Assembly Detail, the general location of this hole. It is equidistant from the ends and 1 inch back from one edge. At that spot, drill a counterbore just deep enough to recess the flange on aT-nut. Then bore through the block for the body of thcT-nut.Tap theT-nut into the hole, and check to make sure that no part of it projects above the face of the block.

Turn the platen over (so the side with the laminate is down), and work out the best location for the attachment block.The location is important, but positioning the block with great precision is not necessary.

Mark the center of the platen surface. Plug the air hose into the air supply port. Now place the remaining 4-inch section of column around the attachment block, and position the two at or near the centermark. The face of the block with theT-nut should be down.

Adjust the column and block away from die center of the platen, if necessary, to ensure that the air hose won't interfere with the movement of the beams. As you can see from the Front View of the Router Duplicator Plan Views. the column should be at least l!/i inches away from the I hose connector. When you're happy with the location, mark it. Then glue and screw the attachment block to the platen. A couplc of I-inch dry wall screws are sufficient. Avoid longer screws unless you're quite certain they won't be penetrating an air passage in the platen.The column section, by the way. remains unattached.

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Wood Working for Amateur Craftsman

Wood Working for Amateur Craftsman

THIS book is one of the series of Handbooks on industrial subjects being published by the Popular Mechanics Company. Like Popular Mechanics Magazine, and like the other books in this series, it is written so you can understand it. The purpose of Popular Mechanics Handbooks is to supply a growing demand for high-class, up-to-date and accurate text-books, suitable for home study as well as for class use, on all mechanical subjects. The textand illustrations, in each instance, have been prepared expressly for this series by well known experts, and revised by the editor of Popular Mechanics.

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