Why are drill bits black, white and gold? What's the difference? Which one is better?

Drilling is a kind of processing method widely used in machining. The drill used in drilling usually has different colors. So what do these different colors mean?

Drilling is a very extensive processing method in the manufacturing industry. I believe that the partners who often work in the drilling line will not be unfamiliar with the understanding of the drill bit. When purchasing the drill bit, the drill bit will have different materials and different colors. What can we do to help with the drill bit of different colors? Is the color related to the quality of the drill bit? Which color is better to buy?

1. Is the color of drill bit related to its quality

First of all, it is impossible to distinguish the quality of the drill bit simply from the color. There is no direct and inevitable relationship between the color and the quality. The processing technology of different color drills is different. Of course, we can make a rough judgment from the color. However, at present, the poor quality bits will also process their own colors to achieve the appearance style of high-quality bits.

2. What's the difference between different color drill bits

High quality fully ground high-speed steel bits often appear in white. Of course, rolling drill bits can also be white by fine grinding the outer circle. The reason for high-quality is that in addition to the material itself, the quality control in the grinding process is quite strict, and the tool surface will not burn. Black is a kind of nitriding treated drill bit. It is a chemical method to improve the tool life by placing the finished tool in the mixture of ammonia and water vapor after 540 ~ 560C ° heat preservation treatment. However, most of the black cutting tools are not used to cover up the black surface of the drill, or to improve the effect of the black surface.

There are three kinds of technology for producing drill bit, black is rolling, the worst. The white ones are trimmed and ground. Because, unlike rolling, there is no high-temperature oxidation, the steel grain structure is not damaged, and it is used to drill workpieces with slightly higher hardness. The yellow brown drill bit is called cobalt bearing drill in the industry, which is the hidden rule of this bit industry. Cobalt containing drill is originally white, ground and produced. When atomized later, it is yellow brown (commonly known as amber), which is the best in circulation. M35 (co 5%) is also gold. This kind of drill is called titanium plating drill, which is divided into decorative plating and industrial plating. Decorative plating has no effect at all. It is beautiful and golden. The hardness can reach hrc78, which is higher than that of cobalt containing drill (hrc54 °).

3. Since the color is not the standard to judge the quality of drill bit, how to buy a bit?

Judging from experience, generally speaking, the white bits are made of high-speed steel, and the quality should be the best. Gold is plated with titanium nitride, which is generally either the best or the worst fool. The quality of black is also uneven, some are made of poor carbon tool steel, which is easy to be annealed and rusted, so it needs to be blackened.

Generally, you can see the trademark and diameter tolerance mark on the drill handle to ensure that the quality of laser or electric corrosion is not too bad. If it is a molded word, if the edge of the word is bulging, the quality of the drill bit is poor, because the bulging word contour will lead to the bit clamping accuracy not meeting the requirements, while the word edge is clear, and the quality of the word at the junction with the cylindrical surface of the drill handle is good. In addition, it depends on the cutting edge of the drill tip. The cutting edge of the fully ground drill bit is very good, and the spiral surface meets the requirements, while the quality of the poor bit is poor at the rear corner.