Tip #28
Table Saw Special Operations (continued)
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Pg. 1-2, Pg 3-4, Pg 5-7

Coving

Figure 4-8. Coves can be produced on the table saw by passing the work obliquely across the saw blade. It requires many passes and the cutting should be done with a combination blade that has set teeth.

Coving is a unique table saw operation in that the work is fed obliquely across the blade (Figure 4-8) It is a lengthy process because the shape is achieved by making numerous passes with the saw blade's projection increased by no more than 1/16" each pass. Coving can be done with the table set at 90° to cut a circular cove or with the table tilted to cut an elliptical cove. If a narrow edge cove is needed, either cut it on a wide piece of stock and cut away the scrap when coving is complete or cut the edge cove from a center cove. Warning: The cutting action is essentially a scraping one, so trying to rush by using more than 1/16" blade projection is not safe. The blade will tend to cut rather than scrape and the action will cause the workpiece to move away from the guide strip and kick back. The first thing to do is

Figure 4-9. Construction details of a parallel rule that will be used to determine the position of the guide strip. Click on image for larger view.

make the parallel rule fixture that is diagram-med in Figure 4-9. The angle of the cut determines the width of the cove. Set the distance between the fixture's long legs to equal the width of the arch you want (Figure 4-10). Next, set the saw blade's projection to equal the depth of the cove and then place the fixture so its long inside edges just touch at the front and rear of the blade. With the parallel rule so positioned, clamp a guide strip to the worktable at the angle determined by the rule (Figure 4-11). The guide strip must be positioned on the infeed side of the blade only so the cutting action forces the stock into the guide strip. The distance between the guide strip and the saw blade will determine whether the cut will be centered, off center, or on an edge of the stock.

Figure 4-10. The distance between the long legs of the fixture should equal the width of the arch.

Figure 4-11. The saw blade's projection should equal the depth of the cove. The guide strip's position is gauged by the parallel rule.

Start the work by setting the blade's projection to no more than 1/16". Use a push block to hold the workpiece firmly against the guide strip and make the pass very slowly. Pay special attention to how you place and use your hands. Warning: Coving is done without the upper saw guard In place so work with extreme caution. Use a feather board and push block to support and guide the workpiece. Never cut edge coves that will be wider than half the stock width. Avoid placing your hands over the blade or in line with the cut. After the first pass, increase the blade's projection another 1/16" and make a second pass. Continue in this manner until you have arrived at the arch's depth.

Figure 4-12. Edge coves are also possible. Make the passes very, very slowly.

This kind of cut can be made on stock edges (Figure 4-12), but be sure of hand position and that the cove is no wider than half the stock width. With all coving operations, you can clamp a second guide strip to the table parallel to the first one. The distance between the strips equals the width of the stock. Thus you have a "road" along which you move the stock. If you wish to speed up the operation, you can do so by cutting kerfs to remove the bulk of the waste material (Figure 4-13).

Figure 4-13. The bulk of the wast removal can be accomplished by making repeat passes with the saw blade.

Figure 4-14. Some of the applictions for workpieces that were formed by cove cutting.

Coving is a useful technique because it can be used to produce components like those shown in Figure 4-14. Shapes like those in Figure 4-15 are possible if the coving is done on pieces that have first been lathe turned. The coves that are formed are not true semi-circles; this could only occur if the work were fed across the blade at right angles to it. However, some work with a drum sander or hand sanding is usually sufficient to true up the arch.

Figure 4-15. Shapes like this are possible by cove cutting after the workpiece has been turned to a cylinder on the lathe.

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