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woodezine - Volume
III - Issue I - January 2005
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Feature
Sponsored by Klingspor
Jointer Station, Page 4
| The Knife Lock Clamp
This looks like the most complicated subassembly in the whole project (Figure 14), but it turns out to be remarkably easy to build. Note that the dimensions here are for a Sears Craftsman (TM) 6-1/4" Jointer (nominally known as a 6"). Two things will change with other brands: the swing arm (piece 25) may need to be longer or shorter, and the jaws of the clamp may need to change to accommodate a differently sized pulley and belt. Build the jaws (pieces 26), hinge (piece 27) and clamp base (piece 28) first, then come back to the swing arm. At that stage, it will be easy to determine the appropriate length visually. |
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| Leaving the cutout for the pulley uncut for a minute, bandsaw the rest of the jaws to fit your pulley. Measure the diameter of the pulley and belt (make sure this is the pulley for the cutterhead and not the one on the motor shaft), then subtract 1/8" from that figure. Using the new number as your diameter, clamp the two jaws together and draw a circle. Use a square to draw lines from the top and bottom of the circle to the edge of each jaw, then band saw this custom cutout for your pulley. Drill holes for the hinge bolts (pieces 29) in the jaws at the locations shown on the drawing, and secure the hinge with lock nuts (pieces 30) and washers (pieces 31). Cut the clamp base to size and shape, then secure it to the deck with two 2" screws driven into countersunk, piloted holes. Don't glue it yet: you may have to move it a bit later on. Center a hole in the clamp base for a 1/4" bolt, washer and wingnut (pieces 32, 33 and 34), and you're ready to determine the length of the swing arm. Unplug the jointer, remove the fence and expose the cutterhead pulley. Dry fit your jaws to the pulley and make any adjustments for a perfect fit. (Look closely at the photo and you'll see that I had to shave the jaw opening a little.) You want the jaws to almost close at the pulley end under pressure, leaving perhaps a 1/16" gap. When the fit is right, notch the bottom edge for the head of a 1/4" hex bolt (piece 35): the notch should be tight enough so that the bolt head can't swivel. On the drill press, bore a 5/16" hole through both jaws, then slide the bolt in place. Secure it with a washer and wing nut. Fit the jaws to the pulley, tighten the wing nut and use the drawing as a guide to measure for the length of the swing arm. For safety reasons, plow the slot in a longer piece of stock before cutting the arm to length, and then bore the hole at the location shown. |
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Assemble the entire clamp and see how
it works. You want it to be able to fold out of the way when not in
use. When everything's perfect, screw and glue the base in position.
Now you're ready to change the knives (Figure 15).
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| Collecting the Chips Sanding belts create fine dust, but cutterhead knives make chips that are too heavy to float in the air. That lets us use gravity instead of a mechanical vacuum to collect the debris from a jointer. All we have to do is let the chips fall into a bin. The base of the bin (piece 36) is MDF, with a 19 degrees angle ripped along its back edge. Cut the sides (pieces 37) from 3/4" MDF, too. Glue and screw the sides to the base, driving countersunk screws up through the bottom into pre-drilled pilot holes. Attach the 1/4" back with screws and glue next: it can be seen, so I used some leftover oak plywood. Attach a small cleat (piece 38) along the inside top edge of the back, cutting its length to fit. The back edge of this cleat needs to have a 19 degrees slope. It's safest to rip the slope on the edge of a wider board, then set the blade back to 90 degrees and rip the cleat off the edge of the wider board. Attach it with glue and lots of spring clamps. |
| Use a couple of screws near the top corners to hold the Plexiglas (TM) front (piece 39) in place while you make up the mitered frame. Rip enough stock for the two frame stiles (pieces 40) and rails (pieces 41), then biscuit, glue and clamp the frame together. make sure the corners are square as you apply clamping pressure. After the glue dries, sand the frame and install it with fourteen countersunk screws driven through the Plexiglas into the MDF sides and bottom. |
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You need to make the holes in the plastic large enough so the screw can pass freely through, or it will crack. Drive five 3/4" screws through the plexiglas into the back face of the top rail of the mitered frame. Again, oversize the pilot holes in the plastic, and countersink the heads. A hardwood handle (piece 42) completes the bin and it's installed with a couple of screws driven from the inside through pre-drilled holes. A pair of shop-built hardwood drawer guides (pieces 43 and 44) are all that's left to complete the construction phase of this project. As the bin will rarely be opened (two or three times a year in most shops to empty the debris), they don't even have to be waxed. In fact, it's better if you don't because a little friction and its own weight will keep the bin in place. Just cut the guides to size and face-glue them together, as shown in the drawing. Then screw and glue them down to the cabinet bottom, countersinking the screw heads. Leave about 1/4" of play (1/8" each side), so the bin is easy to slide. |
| A Shop-tough Finish Given the jointer station's location in our busy shop, I wanted to apply a finish that was tough enough to endure through years of rough handling. After removing all the hardware and small parts, I sanded the entire project down through the grits from 100 to 150 and 220. Then I applied four coats of brushable satin oil-based polyurethane to all the wood surfaces, using steel wool and tack cloths between coats. (Because of scheduling, we took the photgraphs after just one coat.) In use, the station has been an absolute joy. Its profile allows the operator to stand as close to the front of the machine as he/she wants, while maintaining the utmost stability. And the casters let us clear a space in the shop for assembly or materials in a few seconds. Best of all, the slanted back let us spread the casters wide enough to move the center of gravity far to the rear, which is very reassuring when we swivel that 200 lb jointer on its hinge. And the large swing arm catches it at the apex of its travel, so it doesn't tip. While the hinge mechanism makes easy work out of swiveling the jointer for access to its underside, I think it would be fun to add a shock absorber and spring mechanism to help raise and lower it. Perhaps a small gas cylinder on each end would cushion the ride as it is lowers back down, but I have a feeling it might also slow up the progress as you raise it, making the machine heavier rather than lighter. Perhaps a pneumatic cylinder would work. Do any of you engineers out there have an opinion? |
