Twist drill bits

Twist is the most widely-processing tool. Typically diameter range of 0.25 to 80 mm. It mainly consists of
Bit working portion and the shank portion. Work section has two spiral grooves, the shape of twist, hence the name. In order to reduce the guide portion of the hole when electroplated core drill bit intramural friction, twist since the direction of the drill bits tip to gradually reduce the diameter of the shank inverted cone. Twist the 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 rolling or hot extrusion methods such as processing, after the cutting portion is formed by the front end of the drill bits sharpening. Standard twist angle of the cutting portion 118, the chisel edge angle is 40 ° ~ 60 °, the clearance angle of 8 ° ~ 20 °. For structural reasons, the rake angle at the outer edge of the large decreases toward the middle, chisel at a negative rake angle (up to about -55 °), from the squeezing action when sds max drill bits. In order to improve the cutting twist, can be processed in accordance with the nature of the material will be ground into various shapes cutting part repair (such as drill bits group). Shank twist drill bits with and handle the form of two straight shank taper, when caught in the drill bits chuck machining the former, the latter is inserted in the machine spindle or tailstock taper in. General manufacturing high-speed steel twist. Inserts welded carbide blade or crown of twist suitable for machining cast iron, hardened steel and non-metallic materials, solid carbide twist core drill bit for machining small parts and printed circuit boards and other instruments.