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用矩形拉刀拉削方孔,具有尺寸稳定、粗糙度R_α值小,效率高等特点,但常常出现方孔偏离基准、位置度超差的情况,如图1所示。图2所示为矩形拉刀的结构图。由图2可知,在刃磨齿形时,两对称面的齿廓不是一次磨出来的。因此,两对称面的齿、槽尺寸、表面粗糙度、切削刃的锋利程度不一致。这样,拉削时两侧的拉削力是不相等的,拉刀就会向受力小的一侧偏移,使之多切去一部份金属,这就是造成位置度超差的原因。解决上述矛盾的方法有两个,其一是设法改进拉刀的磨削方法,使两侧刀刃一次磨出,可使拉削时两侧受力均等。但这种方法会受到设备的限制和拉刀刚性(特别是拉刀截面尺寸小)的约束。因此,很难实
With rectangular broach pull square hole, with dimensional stability, roughness R_α value is small, high efficiency, but often square hole deviation from the benchmark, the position of ultra-poor situation, as shown in Figure 1. Figure 2 shows the structure of rectangular broach. As can be seen from Fig. 2, the tooth profile of the two symmetrical surfaces is not ground out once during sharpening. Therefore, the symmetry of the two teeth, groove size, surface roughness, cutting edge sharpness inconsistent. In this way, broaching on both sides of the broaching force is not equal to the broach will be forced to the side of the small shift, so that more than a portion of the metal cut, which is caused by the location of ultra-poor reason. There are two ways to solve the above contradictions. One is to try to improve the grinding method of the broach so that both edges can grind out at one time, so that the force can be equalized on both sides during broaching. However, this method is limited by the equipment and the rigidity of the broach (especially, the broach section size is small). Therefore, it is hard to be true