Woodworker's Journal 1994-18-6, страница 20

Popular Carving Bits

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Photo A: "Structured" tungsten carbide burs remose a lot of stock quickls and cut in both directions. Thev come in silver (coarse, aggressive cut) and gold (medium, scmismooth cut).

Once you've bought your power carver, you'll be faced with a selection of hundreds, even thousands, of burs, bite, blades, cutters, abrasive wheels, and other accessories

that you can use to alter wood. However, most professional carvers stick with four basic types of bits.

Carbide burs come in standard and double-cut styles and in a wide variety of sizes, point configurations, and shank diameters, making them the most versatile of all cutters. Carvers like burs because they remove stock quickly and leave a smooth finish (photo A). Use the larger burs for fast stock removal, the finer ones for detailing. Most of these burs and cutters also come in vanadium steel, although steel burs don't last nearly as long as carbide. The single-cut burs (photo B) cut in one direction only.

Tungsten carbide (structured) burs, also called SSG or "kutzall" burs, have a fast, free-cutting action and work equally well operated in forward or reverse modes, with or against the grain. They're used primarily for fast stock removal when roughing out large shapes. Typically, they

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Photo B: Carbide cutlers represent the mainstay of the power carver's arsenal. Thes cur quickly (in one direction only, however) and leave a smooth surface.

leave a rougher surface than directional carbide burs, but can be "dressed" on a diamond stone to produce a smoother finish or to custom-shape the cutting head. The coorse-grit silver burs shown provide the fastest cutting action; the medium-grit gold burs cut more slowly but leave a finer finish. These burs are virtually indestructible and can be used on hardwoods, porcelain, fiberglass, nonferrous metals, marble, and other hard materials. When they get clogged with wood, you simply burn out the materia! with a torch without harming the cutter.

Bird carvers favor ruby bits (photo C) for intricate detailing ond contouring. These long-lasting bits leave an extremely smooth finish requiring little or no sanding, They work equally well in both directions. While some carvers use diamond bits for this purpose, ruby bits have less tendency to clog; they also absorb and dissipate heal more readily, which helps prevent burning the work-piece. Aluminum oxide bits (photo D) produce the same velvet smooth finish as ruby bits, but they cost o fraction as much and come in many more shapes and sizes. The smaller types make a much finer line than do ruby bits, ond you can easily grind them into custom shapes. On

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Photo C: Long-lasting ruby car* in" bits leave an exceptionally smooth finish, resist clogging, and cut in both directions. I se these for fine shaping and detail work.

Photo I): Muniinum oxide hits come in a wide \arietv of shapes and si/es and can be ground into custom shapes. They're much cheaper than ruby bits but relatively short-lived.

the down side, aluminum oxide bits won't last nearly as long as ruby bits, so you'll need to replace them more frequently.

Engraving burs (photo E] come in vanadium steel or carbide. Use these for extremely fine texturing and detail work, such as adding the nostril holes in a bird's bill or applying minute feather textures. When buying any bur, bit, or cutter, pay attention to the manufacturer's maximum speed rating, and don't exceed it. Also, buy the highest quality bits you can afford, since they will more likely be milled true and to exact shank sizes. Cheap bits often run slightly off-center, causing vibration, or the shafts aren't milled to precise diameters, allowing them to slip in the collet.

Photo I : t se engraving details, such as separation tines between a bird's elms and foot or nostril holes in the bill. 1 hey come in saRadiuni steel and longer-lasting carbide.

bits to carve minute

offering seven different motors (Vis to 'A hp) and 22 different handpieces.

Motor options include bench-mounted or hanging models, some with reversible switches. On most, you can adjust the speed with an optional foot pedal or benchtop speed control. Several benchtop models hav e a speed-control dial built into the base. Reversible motors arc especially handy for left-handed users (they direct dust away from the carver) or for achieving a symmetrical look in woods with difficult grain patterns. Some carvers prefer

the foot control bccause it enables them to change speeds while carving; others prefer the bench control so they can move freely around the carving table to attack large workpieces from different angles.

According to Mark Coleman at Foredom, most carvers prefer the %-lip series S motor because it offers ample power for most carving tasks and accepts a variety of handpieces. Operating at speeds of up to 18.000 rpm, the series S comes in a hang-up model and two bench models, one of

which features a dial control in the base. A reversible version, designated SR. is also available. I prefer the hanging motor because it keeps the flexible shaft suspended above the work surfacc. which makes it less likely that you'll knock tools and other stuff off the table while carving. Coleman adds that the three most popular handpieces for carv ing arc the no. 30, no. 44, and no. 8 /photo 3), The no. 30 has a Jacobs-stylc chuck that accepts up to */<:" shanks. The no. 44 has a collet-stylc chuck that accepts seven collets ranging from 'A*"

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November/December 1994

Woodw orker's Journal I