The tapered shank twist drill is the most widely used hole processing tool, usually with a diameter ranging from 0.25 to 80 mm. It is mainly composed of a working part and a shank. The working part has two spiral grooves, which are shaped like twists, hence the name. Unlike straight-shank twist drills, tapered-shank twist drills have a tapered handle. Twist drills of different specifications have different Morse tapers.
The manufacturing process of high-speed steel (W6Mo5Cr4V2) twist drills can generally be divided into rolling and twisting, milling, extrusion, rolling, rolling and grinding, among which there are four methods: rolling and twisting, milling, rolling and grinding. relatively common.
For the group pitch of 15.6-50.5, the hot-rolled twist forming process and milling forming process can be used for mass production, which has been widely recognized and used. Due to the large material consumption during milling and drilling, the manufacturing cycle is long and time-consuming, and the release of production capacity and the improvement of product quality or durability are subject to certain restrictions. For this reason, the company decided to use the hot rolling and twisting process for series products with specifications above 32.5 , rolling is used instead of milling to make up for the shortcomings of the milling process. By improving the rolling and twisting machine equipment, the outer dimensions of the fan-shaped plates were readjusted, and the three-way rolling groove method was adopted to expand the rolling and twisting specifications to 50.5mm.
In order to improve the cutting performance of the twist drill, the cutting part can be ground into various shapes (such as group drills) according to the properties of the material being processed. There are two types of twist drill shank: straight shank and tapered shank. The former is clamped in the drill chuck during processing, and the latter is inserted into the tapered hole of the machine tool spindle or tailstock. Generally, twist drills are made of high-speed steel. Twist drills with welded carbide blades or crowns are suitable for processing cast iron, hardened steel and non-metallic materials. Small solid carbide twist drills are used for processing instrument parts and printed circuit boards.