Bit selection - know the type and use
Drill is widely used in our construction machinery hardware, it is used in the physical material to drill through hole or blind hole, and to the existing hole hole expanding tool. However, the types of drill bits selected by us are also different in different operating environments. The commonly used drill bits mainly include twist drill, flat drill, center drill, deep hole drill and sleeve drill. Reaming and countersinking drills are conventionally classed as drill bits, although they cannot drill into solid material. Below, with small make up together to understand the different types of drill different purposes.
Twist drill is the most widely used hole tool. The usual diameter range is 0.25 to 80 mm. It consists mainly of the working part and the handle. The working part has two spiral-shaped grooves, shaped like mahua, hence the name. In order to reduce the friction between the guide part and the hole wall during drilling, the twist drill gradually reduces the diameter from the drill tip to the shank and presents an inverted cone shape. The helical Angle of the twist drill mainly affects the size of the cutting edge's front Angle, blade blade strength and chip removal performance, usually 25° ~ 32°. The spiral groove can be machined by means of milling, grinding, hot rolling or hot extrusion. The top Angle of the cutting part of a standard twist drill is 118, the bevel Angle of the transverse edge is 40° ~ 60°, and the rear Angle is 8° ~ 20°. Due to structural reasons, the front Angle is large at the outer edge and gradually decreases toward the middle. The transverse edge is negative front Angle (up to about -55°), which plays a role of extrusion during drilling. In order to improve the cutting performance of the twist drill, the cutting part can be polished into various shapes (such as group drill) according to the nature of the processed material. There are two types of shank of twist drill: straight shank and taper shank. The former is clamped in the drill chuck while the latter is inserted in the taper hole of machine tool spindle or tailstock. Generally twist drill with high - speed steel manufacturing. Twist drills with welded carbide blades or crowns are suitable for processing cast iron, hardened steel and non-metallic materials, etc.