Tip #52
Shopsmith Jig Saw (continued)
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Cutting Metal, Plastics, and Paper

Figure 16-31. (A) This plywood table will give you added support when cutting thin metal.

When cutting metal, use a blade with 14 or more teeth per inch. If you're cutting steel or iron, use a "hardened" or tempered blade. These blades are heat treated for longer wear. The recommended speed setting for cutting metal is “Slow.”

Figure 16-31. (B) Construction details of an auxiliary plywood table. Click on image for larger view.

Thin sheet metal tends to bend down along the kerf while you're cutting. To help prevent this, make an auxiliary table of plywood with a throat hole just large enough to accommodate the blade (Figure 16-31). This will give you some extra support around the cutting edge. The frame on the bottom of the auxiliary table keeps it from shifting and the hold-down holds it securely to the jigsaw table.

Figure 16-32. When cutting metal, put one to two drops of oil in front of the blade on the pattern line every 1 "to 2". This helps the blade run cooler and last longer.

Before you start cutting, put one to two drops of oil on the pattern line just in front of the blade. Repeat this every 1" to 2". This will lubricate the blade, helping it to run cooler and last longer (Figure 16-32). Another technique that helps when cutting metal is to lubricate the blade with beeswax. This will help when turning tight corners and will reduce blade breakage.

Figure 16-33. You'll get minimum burring when sawing thin sheet metal if you provide support as close to the cutting area as possible. Here the circle cutting platform is used.

When you're finished, remove the blade and the auxiliary table. Wipe off any oil and/or beeswax that might have gotten on the jigsaw table. Remove the table; then clean away any metal filings from the lower blade chuck and base. This must be done every time you use the jigsaw to cut metal. If you don't, the metal filings may work their way between the moving parts of the jigsaw, causing them to wear prematurely.

Figure 16-34. You can also make a special insert. The size of the hole through the insert should be no more than the blade needs to get through.

One of the problems with metal cutting, especially if the material is thin, is the burrs that will accumulate as the blade cuts. This is normal; the blade might even bend the material at the cut area. To minimize the problem, use an auxiliary table with a blade insertion hole that is slightly larger than the blade. This can be the platform that you may have made for pivot cutting circles (Figure 16-33) or a special insert of 1/4" hard board (Figure 16-34). Both methods will provide support at the cutting area to minimize burring and bending. Another way to avoid burrs and bends is to sandwich the work between sheets of thin ply-wood (Figure 16-35).

Figure 16-35. Another way to saw thin sheet metal is to sandwich it between thin plywood.

Cutting Plastics-When cutting plastics, use a skip-toothed blade. The extra space between the teeth helps to clear away the chips. The blade runs cooler and the workpiece doesn't get as hot. Regular woodcutting blades sometimes create so much heat that the plas-tic chips weld together and the blade binds.

Figure 16-36. Leave the protective paper on the plastic when you make the cut.

Leave the protective paper on the plastic when you cut (Figure 16-36). This will keep it from getting scratched. If the plastic melts, you may be feeding the workpiece too slowly or the speed may be fast.

Figure 16-37. A pad of paper can be cut on the jigsaw; but, to avoid jagged edges, the sheets must be sandwiched between thin plywood.

Pad Sawing Paper-Sawing paper becomes a simple procedure when the sheets are sandwiched between thin plywood (Figure 16-37). The paper should be large enough so the nails holding the pad together can go through it in an area that is outside the pattern. If the edges of the sheets are to be bent back or otherwise hidden, the hole locations don't matter. Paper cut in this manner will have remarkably smooth edges.

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