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Drilling and Boring Tools

Holesaw and circle cutter; Specialty bits
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Holesaw and circle cutter; Specialty bits

Holesaw and circle cutter. Instead of taking out the inside of a hole as chips, you can remove it in one chunk with a holesaw or circle cutter, both shown left. They're the tools to turn to when you need a really large hole.You'll find holesaws up to 6" in diameter and circle cutters that adjust to 8" or more.

Holesaws use fixed-size cutters. The cup-shaped blade fits onto a mandrel equipped with a twist drill in the center. The drill bit acts as a pilot for the tool.

The circle cutter (sometimes called a fly cutter) adjusts to any diameter within its range. It also employs a twist drill for a pilot, but cuts with a single blade.

With either, the inside depth of the tool limits the cutting depth. To go through thick stock you can drill as far as the tool will go, flop the workpiece, then drill from the back, using the pilot hole as a guide. With a holesaw, you can withdraw the tool when it bottoms out, break the core out of the stock, then saw farther.

Clamp the workpiece firmly when using either one. Holesaws, especially those 1" or less, work well with a portable drill (but hang on tight). Larger holesaws and any size circle cutter should be used only in the drill press. Limit the speed for either tool to250 rpm.

Specialty bits. If you use a lot of screws in your projects, check out screw pilot bits. These inexpensive bits drill the pilot and shank holes for a screw and form a countersink for the head, all in one operation. Other bits of this type counterborte for a plug. The three bits at the lower left side of Photo 10, below, are typical.

For attaching hinges and other hardware, a Vix bit, shown at the upper right of the photo, comes in handy. A sleeve on this bit fits into the countersunk screw hole on the hardware item, automatically centering the bit, which then extends from the sleeve to drill the screw pilot hole.

An expansive bit like the one shown in Photo 11, below, bores holes of many sizes. A sliding cutter sets the diameter -- useful if you need to bore odd-sized holes. The two available sizes cover a range of hole diameters from 5/8" to 5". Interchangeable cutters give the bit shown a range of hole diameters from 5/8" to 3". Power-drilling with one can be problematic, though. You'd be better off using one only with your brace.


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Continued on page 5:  General Tips for Drilling

 

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