Tip #52
Shopsmith Jig Saw (continued)
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Cutting Circles

Figure 16-30. (A) A special platform, clamped to the table, lets you pivot cut cfrcles. Be sure the holes for the pivot nail are in line with the tips of the saw teeth.

You can cut accurate circles using the pivot technique if you make a special platform to clamp to the table as shown in Figure 16-30. The platform, a piece of 1/4" plywood, has a series of equally spaced holes drilled on a common centerline. The pivot is a nail pushed through one of the holes; its distance from the blade is equal to the radius of the circle.

Figure 16-30. (B) You can start the job by using a blade insertion hole or by making a lead-in cut before mounting the work on the pivot. The pivot nail does not have to be as long as the one shown here.

The work is center-drilled to fit over the nail and then rotated against the blade to make the cut. To start the cut, you can either drill a blade insertion hole or make a lead-in cut to the line before placing the work over the pivot. Be sure the holes in the platform line up with the tips of the saw teeth and that you rotate the work only as fast as the blade will cut.

If the jigsaw is mounted on the Mark V, you can use an unusual but effective setup to pivot cut very large circular pieces. Mount the rip fence on the worktable and place the lathe cup center in the hole in the top of the fence (Model 500) or in a hole drilled in a fence extension that is attached to the fence (Model 510). Adjust the height of the worktable so the point on the cup center is a bit higher than the jigsaw table. The distance from the cup center point to the jigsaw blade will be the radius of the circle. When you work this way, the chucks will have to be indexed.

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