Abstract:
During the manufacture of a bandsaw blade, a rotary hone forms, in a clearance side of each tooth, a narrow flat land. A leading edge of the land defines a sharp cutting edge. The land has a width no longer than ten percent of the pitch distance of the teeth.

Description:
BACKGROUND 
     In power sawing of metals with bandsaws, the cutting depth per tooth is about 10 micrometer, which is of the same order as the depth variation between teeth produced by milling or grinding the teeth in traditional ways. This means that the cutting work will basically be concentrated to a few teeth, which are then subjected to unnecessary wear, if no special procedures are used. It is then commonly recommended that the first cuts with a new sawblade are made with much less feed force than what is normally intended to be used in normal sawing. Hereby the teeth are worn to a fairly even height without risk of overloading. However, in spite of the low loading it is unavoidable that some of the cutting edges will be rounded-off so that the cutting forces increase. 
     It is known from other tools where all edges are parallel, such as milling cutters, that one can after mounting of the cutter in the machine rotate it against a hard abrasive hone, which at the same time makes all edges sharp and equally high, which may be pertinent when cutting inserts are replaced. On finished metal sawblades the edges are normally not parallel but set to various angles to both sides. The method of running against a hone after mounting in the bandsaw machine can thus not be used. 
     A problem especially encountered at bandsaws is vibrations in the plane of the sawblade, caused by sharp edges with large clearance angle being able to penetrate into the metal with so low feed force and so little difference between increasing and decreasing cutting depth, that all teeth engaged in cutting will produce vibrations with the same frequency, and since the cut bottom surface will become corrugated, they will amplify each other&#39;s vibrations. Recently mounted sawblades will cause a very annoying high frequency noise, which will be reduced when the teeth get somewhat worn, since there will then be more of a difference in feed force between increasing and decreasing cutting depth. 
     The present invention concerns a bandsaw blade and a method for manufacture of bandsaw blades, where all cutting edges are sharp before use, and where all edges in a group with equal lateral slope also have equal cutting depth. Such a sawblade can immediately be used for cutting with full feed and cutting speed, it will wear more slowly than a sawblade according to prior art, and it will from the beginning produce less noise. 
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  shows one stage in manufacture of a bandsaw blade, after forming the profile of the teeth by milling, grinding or brazing of carbide cutting edges, but prior to setting of the teeth as required, and prior to joining the band ends to form loops.  FIG. 2  shows a cross-section of the band after setting. 
     A bandsaw blade  20  according to the invention includes two long sides  20   a , two thin edges  20   b  and cutting teeth, wherein all cutting teeth of the blade are disposed on one of the thin edges. The teeth may as shown in  FIG. 2  be made with several groups of teeth, where the teeth in each group have equal lateral slope of the edge. Such groups can be set right  21 , set left  22  or straight  23 . The number of groups may also be more than three, by having two groups set right with different setting distance and angle, and correspondingly for those set left, The bandsaw blade may also be made with all teeth straight. 
     A backside  30  of a leading one of each pair of successive teeth extends downwardly from a respective flat land  12  in a direction which is inclined toward the trailing tooth. A front side of the trailing tooth extends downwardly from a respective cutting edge  14 . Lowermost ends of the backside and front side join one another to form an upwardly open concave gullet  32  separating the two teeth. 
     The teeth are supposed to have basically the same height before setting, with edges  24  at right angles to the plane of the blade. Due to wear or irregularities of the tools for forming the teeth, they will originally have some variation in height, which is small compared to the height, but comparable to the cutting depth per tooth. According to the method used in grinding or milling, the tooth edges are commonly uneven or rough, and the surfaces adjoining the edge may have crosswise scratches. Such edges are liable to get further damage by chipping or similar deformation. The previously mentioned method using low feed velocity and reduced power during the first few cuts will remove the scratches and lengthen the lifetime of the edges. It has also been suggested to remove the scratches by blasting or other abrasive methods which at the same time will make the edges slightly rounded, resulting in a stable sawing but requiring increased cutting force. 
     At a bandsaw blade according to the invention, the scratches are removed before the final steps of manufacturing the saw blade by honing with a fine grain abrasive material against the tooth tips. By this method the teeth get very sharp cutting edges  14 , narrow scratch-free lands  12  on the clearance side and equal height. This makes it possible to use full cutting force and full cutting depth from the beginning, and the lands ensure stable chip formation. The lands  12  cause a greater feed force if the cutting depth increases, and a smaller feed force if the cutting depth is reducing, compared to teeth according to prior art. The force variation will then have such a time cycle which completely prevents the teeth from amplifying the vibration of each other, and bandsaw blades made according to the invention have been shown to reduce the noise by as much as 20 decibel. The width of the lands should not exceed 10 percent of the pitch distance P between teeth, since friction on wider lands will need a greater cutting force. Also, the land width W, measured in a longitudinal direction D of the tooth, is shorter than a length L of each tooth and shorter than both a thickness T and a height H of each tooth, as is apparent from  FIG. 1 . 
     A method of manufacturing a bandsaw blade according to the invention comprises pulling the toothed blade  10  across one or more abrasive hones  11 , which to avoid uneven wear of said hones are preferably made to rotate slowly. The axis of rotation  15  is preferably parallel to the plane of the saw blade but laterally offset relative to said plane. Through rubbing against the hones each tooth gets a flat land  12  on the clearance side, all said lands being in the same plane  13 , and originally occurring variations in tooth height leading to variations in width of the lands  12 . The leading edge of each land  12  is a cutting edge  14 , which by the honing is sharper than without honing. The teeth forming each group thus is have edges and lands at equal height before setting, and will retain equal height after setting, since members of each group have equal setting angle and setting width. 
     By using slowly rotating hones there is an additional advantage that different points on the hone will move in different directions over the land  12 , all of them having a velocity component entering the land from the edge  14 , which compared to lengthwise grinding or fixed hones produces much smoother lands with less friction and especially in comparison with crosswise grinding ensures improved edge durability, since crosswise scratches may start fatigue chipping. 
     The material of the hone is chosen with reference to the material of the teeth, and may preferably be fine-grain diamond or boron carbide with an elastic binder. The slow rotation of the hones will occur automatically if the axis of rotation  15  is offset a distance not exceeding half the radius of the hone, if desired combined with a slight braking. It would also be possible to have a powered rotation of the hone fitted to the feed velocity of the saw blade. 
     Another type of hone could be one or more cylinders with large diameters and rotation axes parallel to the edge plane  13  but deviating from the length direction of the blade by an angle small enough to ensure a long enough contact time between each tooth and the hone.