Straight shank twist their different functions can be divided into three parts:
- The drill bit shank with clamping portion altar, and the power required for transferring drilling (torque and axial forces).
- Drill neck portion cutter located in the transition between the body and the shank. Typically used as empty sipes wheel retract used.
- The working portion of the drill bit body. The cutting portion (ie drill tip) and guide parts.
Straight shank twist drill parameters:
In order to reduce the guide portion of the bore wall friction during drilling, straight shank twist drill tip from the shank progressively reducing the diameter of an inverted cone. Straight shank twist helix angle of the cutting edge mainly affects the size of the front corner, edge flap strength and chip performance, usually 25 ° ~ 32 ° .
Spiral groove available milling, grinding, hot-rolled or hot extrusion methods such as machining, forming the cutting portion after grinding through the front end of the drill. Cutting portion standard straight shank twist angle is 118, chisel edge angle is 40 ° ~ 60 ° , after the angle of 8 ° ~ 20 ° .
For structural reasons, the rake angle at the outer edge of a large, gradually decreases toward the middle of the chisel edge at negative rake angle (up to -55 ° ), since compression when drilling. In order to improve straight shank twist cutting, according to the nature of the material to be processed will be ground into various shapes cutting portion repair (such as drilling group).
Shank straight shank twist forms with and handle two straight shank taper, the processing of the former caught in the drill chuck, which is inserted in the cone of the machine spindle or tailstock.
Usually straight shank twist manufacture high-speed steel. Inserts welded carbide blade or crown of straight shank twist drill suitable for machining cast iron, hardened steel and non-metallic materials, solid carbide straight shank twist drill for machining small parts and printed circuit boards and other instruments.
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