According to different processing methods, the twist drills currently on the market are roughly divided into the following types:
1. Rolled twist drill
After the high-speed steel is heated and burned red, the shape of the twist drill is quickly rolled out at one time. Afterwards, the twist drill only needs to be heat-treated and surface-treated to sharpen the head before it can be used.
The biggest advantage of the process is high production efficiency and full utilization of raw materials; the internal structure of the processed drill body has fiber continuity, and the grains are refined, the carbides are evenly distributed, and the red hardness is high.
However, the rolling process also has obvious defects, that is, the drill body is very easy to crack, or there will be some cracks that are not easy to detect, and because it is formed at one time, the overall precision of the drill will not be particularly high.
At present, twist drills still generally adopt this processing method, so the rolled twist drills in the foreign trade market are mainly medium and low grade.
2. Groove grinding back twist drill
Due to the phenomenon that rolling is easy to form cracks, more than 98% of the cracks in rolling twist drills occur at the intersection of the land and the groove.
However, first rolling out the edge groove of the drill on the rolling mill, and then finely grinding the outer circle on the machine tool, perfectly solves this problem.
And through the process of fine grinding the outer circle, not only can the problem of cracks be solved, but also the machining accuracy of the drill bit and the accuracy of radial circular runout can be improved.
3. Fully ground twist drill
At present, the most mainstream twist drilling technology in the world, twist drills are all made of grinding wheels from the cutting of material, to groove grinding, back grinding, edge cutting and angle cutting.
The fully ground and polished twist drill has a beautiful and smooth appearance, and the key dimensions such as radial runout, core thickness, and core thickness increment have been very well controlled, and the precision is extremely high.
However, in fact, as long as the rolling process and heat treatment level are in place, rolling is still better from the perspective of durability.
Post time: Aug-15-2023