Improvements Through Research on Thin Circular Sawblades

Experimental work was conducted with special thin circular sawblades to solve problems in sawing pencil slats from blocks of incense-cedar (Libocedrus decurrens Torrey) 2.63 by 2.8 by 7.25 inches. Engineering aspects selected for study were blade flatness, vibration, thermal effects, blade geometry and tensioning. Results of this continuing research drew the following conclusions and recommendations: 1) Thin, tapered blades can and should be made and maintained flat without hammering. 2) Vibration of a rotating blade can be prevented by proper manufacture; by avoiding extraneous vibrations, including axial movement of the arbor; by avoiding critical speeds of rotation; by using large and accurate collars; and by avoiding objectionable thermal stresses. 3) Thermal stresses caused by heating near the rim should be prevented. A flat, smoothly rotating blade avoids excessive lateral rubbing. Cooling outer zones or heating inner zones reduces the thermal gradient. Expansion apertures cool the blade and relieve compressive stresses near the rim. Tensioning counteracts such stresses. It does not compensate for the expansion of the rim due to centrifugal force, but, on the contrary, augments it. 4) Thin blades can be tipped with tungsten carbide without danger of annealing or buckling. Diameter and rim thickness of a tapered blade can thus be kept constant. 5) Thin, tapered, carbide-tipped blades, mounted on a suitable machine, can saw incense-cedar to a depth of 2.6 inches with kerf of less than 0.050 inch at 75 feet per minute.

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