Saw blade

Abstract: A saw blade for sawing of wood has sides (12) with an uneven synthetic powder lacquer coating (15) with friction properties like the cut wood surfaces (13) to remove the sawdust from the kerf without adhering to either surface, thereby lowering the cutting force and improving the straightness of the cut.

Description: Background Saw blades for sawing of wood have traditionally been made with the flat sides smoothly ground or coated with smooth rust-proofing lacquer, to reduce the friction between the saw blade and the sides of the kerf. It is also known to make the sides of the saw blade with sharp cutting or abrasive elements, to improve the smoothness of the cut surfaces by shaving or filing after the teeth have done their cutting, as described in the patents US 4,102,231, DE 3 838 844 and SU 821136. Such saw blades create large friction and require large forces, and they have not been widely used. According to the invention a saw blade can be made with side surfaces, the structure of which assists in removing sawdust from the kerf without removing any substance from the cut surfaces. This lowers the friction considerably, and makes the saw blade less affected by lateral forces, thereby improving the smoothness and straightness of the cut. Description of the invention A section of a saw blade according to the invention is shown in the figure. The saw blade may be part of a hand tool or of a power tool, such as a circular saw or a sabre saw. The saw blade has side surfaces (12) and, along at least part of the periphery, teeth (11) which cut a kerf in the workpiece with a width exceeding the thickness of the saw blade. The teeth can be wider than the thickness of the saw blade or as shown in the figure set alternatingly to the left and right side. During sawing sawdust (16) will collect in the space (14) between the cut surfaces (13) and the sides (12) of the saw blade, causing increased friction. If the sawdust is not equally distributed, it may force the saw blade to the side causing a crooked or uneven cut. During sawing with a saw blade of traditional type with smooth sides (12) each particle of sawdust (16) in the space (14) will be affected by a noticeable friction force from the cut surface (13) and by a very small force from the side (12) of the saw blade, with the result that the sawdust stays in the space (14), gradually becoming compacted and adhering to the cut surface. The cutting force will increase until the saw blade is lifted clear of the workpiece and the sawdust removed. During sawing with a saw blade with abrasive or cutting elements on the sides, each particle of sawdust (16) will be affected by a noticeable friction force from the cut surface (13) and a very large force from the elements on the sides, with the result that the sawdust will slide and rub against the surface (13) but follow the motion of the saw blade with a strong tendency to adhere to the saw blade. The cutting forces increase when many particles adhere, and it may become necessary to lift the saw blade clear of the workpiece to remove adhering particles manually. A saw blade according to the invention has side surfaces (12) with an organic coating surface structure which for friction and graininess corresponds to the cut surfaces (13). Each particle of sawdust (16) will the be affected by equally large friction forces from the cut surface (13) and from the sides (12) of the saw blade, with the result that the sawdust particles are kept rolling between the surfaces without adhering to any of then, and are finally transported out of the kerf with a velocity corresponding to half the velocity of the saw blade. This surface structure is preferrably achieved by dry powder lacquering, forming a layer (15) on the side surfaces (12) of the saw blade. The grain size and firing temperature of the lacquer is chosen to give a grainy surface with a grain size about 0.3 to 0.6 mm and a profile depth about 0.15 to 0.05 mm peak to peak Suitable types of lacquer are epoxy, polyester or mixtures of these. This surface structure feels clearly uneven to touch. The convex grain surface peaks should be more rounded than the concave grain surface troughs to minimize abrasion. The thickness of the layer (15) should be less than the amount of set of the saw teeth (11) to ensure sufficient space (14) between the cut surface (13) and the lacquer layer (15). Tests with a saw blade with grain size 0.5 mm and profile depth about 0.07 to 0.10 mm in resinous wood shows that the cutting force is lowered by 20 % and that no sawdust will adhere to either the cut surfaces (13) or the sides (12) of the saw blade. The invention can be applied to any kind of saw blade which is not appreciably deformed during sawing, such as handsaws, sabre saws and circular saws, but not to bandsaws which for their proper guidance depend on sliding contact with metallic guide devices.

Claims: Saw blade for sawing of wood wherein the side surfaces (12) have an organic coating, characterized in that the coating has an uneven surface structure with a profile depth of 0,05-0,15 mm peak to peak. Saw blade according to claim 1, characterized in that the coating being a synthetic powder lacquer (15) based on epoxy, polyester or mixtures of these. Saw blade according to claim 2, characterized by the peaks of the coating surface being more rounded than the troughs.

Inventors: BLOOM BERTIL, BLOOM, BERTIL
Applicants: KAPMAN AB
Application year: 1993
Main classification: B27B33
IPC codes: B23D61, B27B33