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A radial arm saw is a cutting machine consisting of a circular saw mounted on a sliding horizontal arm. Invented by Raymond De Walt in 1922, the radial arm saw was the primary tool used for cutting long pieces of stock to length until the introduction of the power miter saw in the 1970s.
In addition to making length cuts, a radial arm saw may be configured with a dado blade to create cuts for dado, rabbet or half lap joints. In addition some radial arm saws allow the blade to be turned parallel to the back fence, allowing a rip cut to be performed.
Unlike most types of woodworking machinery, the radial arm saw has a clear genesis: it was invented by Raymond De Walt of Bridgeton, New Jersey. De Walt applied for patents in 1923, which were issued in 1925. De Walt and others subsequently patented many variations on the original, but De Walt's original design (sold under the moniker Wonder Worker) remained the most successful: a circular saw blade directly driven by an electric motor held in a yoke sliding along a horizontal arm that is some distance above a horizontal table surface. A saw which combines the sliding and compound features is known as a sliding compound miter saw or SCMS.
Before the advent of the radial arm saw, table saws and hand saws were most commonly used for crosscutting lumber. Table saws can easily rip stock, but it is awkward to push a long piece of stock widthwise through a table saw blade. In contrast, when a radial arm saw is used for crosscutting, the stock remains stationary on the saw's table, and the blade is pulled through it.
Beginning about the late 1970s, the compound miter saw began to replace the radial arm saw, but only for crosscuts and miter cuts since miter saws are unable to perform rip cuts. The radial arm saw can be less safe when used by an inexperienced or untrained operator, but is not as dangerous when used properly. In the hands of an experienced operator, the radial arm saw can safely cut compound miters necessary for picture and door frames, rip lumber precisely to width, cut tongues and grooves, and make variable dadoes. Like the compound miter saw, the radial arm saw can make these cuts with absolute precision, but is capable of making a wider variety of cuts, including more complex ones.
In the home shop the radial arm saw is an alternative to the table saw. Both machines can rip, crosscut, do simple and compound miters, dado, mold or shape, make tenons, make open mortises, taper cut, and rabbet. The radial arm saw requires less clearance or space in the shop to handle long stock, since it only requires clearance on the sides, whereas a table saw needs clearance to the sides, in front and at the back. The radial saw is perfectly efficient backed up against a wall, whereas the table saw wants to be placed in the center of the shop to give all around clearance. With some accessories the former can be used as a shaper, a disk or drum sander, a grinder, a surface planer, a router, a horizontal boring machine and even as a power unit for a lathe; whereas a table saw's secondary uses are limited to shaper and disk sander. The major shortcoming of most current radial arm saws for home-use is that, most radial arm saws that have been built after the early 1960s are manufactured with stamped sheet metal parts and are machined to loose tolerances, hence they are not precise for doing accurate work without 'tuning'. A high-quality radial arm saw has carefully machined track arm ways and locking mechanisms, and a motor that runs very smoothly; under 'no-load' conditions most of the sound and vibration will originate from the whisper/whistling and the imbalance of the saw blade upon the arbor.
Radial arm saws require a blade with a very low or negative hook angle, to inhibit overly fast feed rate, binding, and the blade's tendency to try to climb the material.
Also a 10 deg. positive hook blade with a "triple chip profile" works well on the radial arm saw and can be considered a universal blade. If the saw climbs with this blade the yoke roller bearings need to be adjusted and tightened.
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