For the brake drum turning, the CBN inserts processing efficiency is about 5 times higher than the carbide tools, and the durability is higher. Such as the solid 

CBN inserts CNGN120716, CNGN120412 or tipped PCBN inserts, CNGA120412.

The brake drum is one of the important components in the brake system of the car. The commonly used material is HT250 gray cast iron. After casting, it is generally not 

allowed to have cracks, slag inclusions, pores and other defects. If there are brake drum blanks with more hard spots, it is more difficult to machine, which requires more 

choices and suitable processing technology and cutting tool selection. Compared with coated carbide tools, CBN turning inserts are better and could realize the high speed,

high efficiency and high precision machining of brake drum.

At present, the main material of the brake drum on the market is gray cast iron, the gray cast iron has good shock absorption and wear resistance, and the noise is small, 

and the processing technology is simple. The general processing technology is Casting - roughing - semi-finishing - finishing - drilling - inspection.

1) Casting: The brake drum has two types: integral casting type and combined casting type depending on the type of construction. When casting, it is necessary to control the

quality of the charge, the chemical composition of the molten iron, and control the pouring temperature, the correct ingredients, such as poor control, there may be casting defects,

such as sand, pores, white mouth, etc., the above casting defects will bring the processing difficult.

2) Roughing: After casting, it enters the machining workshop. At present, the processing brake drum often uses a numerically controlled lathe, the reason is to reduce the scrap rate

of the workpiece, and improve the processing efficiency. Rough turning the brake drum needs to have an allowance of about 0.5mm for semi finishing and finishing to ensure the finish.

3) Semi-finishing: In order to obtain a high degree of smoothness of the brake drum, semi-finishing is generally performed after roughing, leaving an allowance of 0.1-0.2 mm for the 

finishing process.

4) Finishing: In order to obtain a high surface finish, it is generally refined after semi-finishing to the required dimensions of the drawing and the finish of Ra1.6.

5) Drilling: Drill holes of corresponding size in the required parts of the drawing.

6) Inspection and storage: Check the surface finish of the brake drum, and whether the dimensional tolerance meets the requirements of the drawings. If it is qualified, it can be assembled.