Chapter 2, Lesson 4 of 4
GOAL: To understand how jigs can expand the versatility of the table saw and to learn how to build several useful jigs.
A table saw’s repertoire of four basic operations — ripping solid wood, crosscutting solid wood, cutting manufactured sheet material (MSM) and shaping solid wood and MSM — can be expanded by using a structure to hold a workpiece firmly in place and guide it past the saw blade so that it can be cut in some particular way. This structure is typically called a jig, and this lesson will explain how to build several jigs dedicated to particular functions.
The jigs described here are used to hold the workpiece while an uncommon cut is made or to hold a workpiece so that an angle cut can be made with the blade in its normal 90° position. Most jigs are built with a combination of two or more of the following materials: solid wood, plywood and medium-density fiberboard (MDF). You can cut most of what you’ll need on a table saw, although a miter saw is also useful. You’ll also need measuring tools: a straightedge, squares, a sliding bevel and a rule or tape. Two cordless drills are useful, one with a countersink and pilot-hole bit, the other with a screwdriver bit. A pneumatic nailer will substitute for screws in most situations, making assembly easier and faster. Clamps are essential.
The principles and utility of a basic jig are well illustrated when you have to rip a straight line on a board of which neither edge is straight. The photo at right shows a board with a waney edge and sapwood on one side and a curved band saw cut on the other. Either edge can be cut straight along any line you choose by hanging it over the straight edge of a baseplate.
The workpiece is held on a 3/4" thick baseplate with stop blocks and hold-downs. If the desired sawn edge is difficult to gauge by eye, snap a chalk line on the workpiece to help you position it on the baseplate. Hold the stop blocks tight to the ends of the workpiece and screw in place.
Make them 1/16" less than the thickness of the workpiece so that when the hold-downs are screwed down onto the stop blocks, the workpiece is firmly held.
To make the cut, set the saw fence to the width of the baseplate and extend it fully across the table. Use the splitter, top guard and push sticks during the cut. If you want to then make the second edge parallel to the first, remove the workpiece from the jig and rip the second edge on your table saw against the fence.
This jig cuts tapers on two sides of a square leg for a table or chair. Taper-cutting is not an everyday task, and this jig is so simple that it takes little time to relocate the fence and stop blocks for another set of tapers, or to make a new version of the jig.
Mark the taper you want on the workpiece, then position it on the baseplate, hanging the excess wood over the edge. Next, clamp the workpiece and baseplate together so you can easily position and fix the fence and stop blocks.
Attach the fence to the baseplate so it’s tight to the back of the leg. Screw the stop blocks into place at each end; note that they won’t be at right angles to the edge of the baseplate because the workpiece is aligned with the taper. Mount the toggle clamps on 2 x 4 material and adjust them so they hold the workpiece down tightly. Make a trial pass with the saw turned off to confirm the clamps are located inboard of blade, guard and saw. You can taper two adjacent faces with a single jig setup. If you want to taper all four faces, you’ll need to move the jig fence or make a second jig.
This jig enables you to saw the molding on the edges of a raised and fielded panel. The advantage of sawing rather than using a router bit is that you can make the cut at any angle and to any depth. To determine the angle of the buttresses and the fence, draw the panel detail at full size. Set a sliding bevel from the drawing and lay out the angle on one of the rectangular buttress blanks. Cut the buttresses. Square layout lines across the baseplate where the buttresses will go. Locate the end buttresses so the fence overhangs by 2" on each end to provide room to clamp the workpiece in place. Align the buttresses on the baseplate, using the back edge as a register. Drill clearance holes through the baseplate on the layout lines and countersink both sides.
Glue, clamp and screw the buttresses in place. Position the jig fence on the angled edges of the plywood buttresses, keeping its bottom edge parallel to the table. Draw layout lines, drill clearance holes, apply glue and screw the fence in its final position.
When using the jig, use the saw table as a guide to attach the panel correctly to the fence. Clamp the panel at each end, set the table saw’s fence to width and extend it fully across the table. To saw the boundaries of the panel’s center-field transition, set the saw blade to height and make these shallow cuts with the panel flat on the saw table.
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