6 problems that must not be ignored in tool grinding

1. Tool materials

In tool grinding, the common tool materials are: high-speed steel, powder metallurgy high-speed steel, carbide and PCD, CBN, ceramics and other superhard materials.High-speed steel cutting tools are sharp and have good toughness, while carbide cutting tools have high hardness but poor toughness.The density of carbide cutting tools is obviously greater than that of high-speed steel cutting tools. These two materials are the main materials of drills, reamers, milling cutters and taps. The performance of powder metallurgy high-speed steel is between the above two materials and is mainly used for manufacturing rough milling cutters and taps.

High-speed steel cutting tools are not very sensitive to collision because of their good material toughness. But carbide cutting tools have high hardness and brittleness, are very sensitive to collision, and the blade is easy to jump. Therefore, in the grinding process, we must be very careful about the operation and placement of carbide cutting tools to prevent collision between cutting tools or cutting tools from falling.

Because the precision of high-speed steel cutting tools is relatively low, and the grinding requirements are not high, plus the price is not high, many manufacturers set up their own cutting tools workshop for grinding. But carbide cutting tools often need to be sent to professional grinding centers for grinding. According to the statistics of some domestic cutting tools grinding centers, more than 80% of the cutting tools sent to repair are carbide cutting tools.

2. machines for Tool grinding: Because the tool material is very hard, so generally can only be used to change its shape by grinding. In the manufacturing and grinding of cutting tools, there are the following kinds of common tool grinders:

a. Grinding slot machine: grinding groove or back of drill, end mill and other cutting tools.

b. Grinding top angle machine: grinding conical top angle of drill (or eccentricity after angle).

c. Repair transverse edge machine: correct the transverse edge of drill.

d. Manual universal tool grinder: grinding outer circle, groove, back, top angle, transverse edge, plane, front knife surface, etc.. It is often used for cutting tools with small number and complex shape.

e. CNC grinder: generally five-axis linkage, function determined by software. Generally used for grinding large number of cutting tools, high precision requirements, but not complex cutting tools, such as drill, end mill, reamer, etc. The main suppliers of this kind of grinder are from Germany, Switzerland, the United States, Australia and Japan.

3, grinding wheel

1. Abrasive

Abrasives of different materials are suitable for grinding cutting tools of different materials. Different parts of the cutting tool need to use different sizes of abrasive to ensure the best combination of blade protection and processing efficiency.

Aluminum oxide: used for grinding HSS cutting tools. The grinding wheel is cheap and easy to correct into different shapes for grinding complex cutting tools (corundum).

Silicon carbide: used to correct CBN grinding wheel and diamond grinding wheel.

CBN (cubic boron carbide): used for grinding HSS cutting tools. High price, but durable. Internationally, the grinding wheel is represented by B, such as B107, where 107 indicates the size of the abrasive particle diameter.

Diamond: used for grinding HM cutting tools, high price, but durable.The grinding wheel is represented by D, such as D64, where 64 indicates the size of the abrasive particle diameter.

2. Shape

In order to facilitate the grinding of different parts of the tool, the grinding wheel should have different shapes.The most commonly used are:

Parallel grinding wheel (1A1): grinding top angle, outer diameter, back, etc.

Disc grinding wheel (12V9, 11V9): grinding spiral groove, milling cutter, auxiliary cutting edge, repair transverse edge, etc.

After a period of use, the shape of the grinding wheel needs to be modified (including plane, angle and rounding angle R).The grinding wheel must often use cleaning stone to clean the chip filled between the abrasive particles to improve the grinding ability of the grinding wheel.

4, grinding standard

Whether you have a good set of tool grinding standard is to measure whether a grinding center is professional.In the grinding standard, the technical parameters of the cutting edge of different cutting tools in cutting different materials are generally stipulated, including the cutting edge inclination angle, top angle, front angle, back angle, chamfer, chamfer and other parameters (in the carbide bit, the process of blunt cutting edge is called "chamfer", the width of the chamfer is related to the cutting material, generally between 0.03-0.25mm.The process of chamfering on the edge (tip point) is called "chamfer". Each professional company has its own grinding standards summarized over many years. The difference between HM bits and HSS bits:

HSS bits: the top angle is generally 118 degrees, sometimes greater than 130 degrees; sharp blade; relatively low requirements for accuracy (blade height difference, symmetry, circumferential run).There are a variety of modifications for the horizontal blade.

HM bits: the top angle is generally 140 degrees; straight slot drills are often 130 degrees, and three-edge drills are generally 150 degrees. Blades and tips (edge) are not sharp, and are often passivated, or called back edges and chamfers; high requirements for accuracy.The horizontal blade is often modified into an S-shaped shape to facilitate chip cutting.

Back Angle:

The back angle of the blade is very important for cutting tools.The back angle is too large, the blade is easy to jump and easy to "stick the knife"; the back angle is too small, the friction is too large and the cutting is not favorable.

The back angle of the tool varies with the different cutting materials and types of cutting tools and tool diameters. Generally speaking, the back angle decreases with the increase of the tool diameter. In addition, the cutting material is hard, the back angle is smaller, otherwise, the back angle is larger.

5, tool testing equipment

Tool testing equipment is generally divided into three categories: knife instrument, projector and universal tool measuring instrument. The knife instrument is mainly used for knife preparation (such as length) of CNC equipment such as machining centers, and is also used to detect parameters such as angle, radius and step length; the function of the projector is also used to detect parameters such as angle, radius and step length. But the above two can not generally measure the back angle of the tool. The universal tool measuring instrument can measure most of the geometric parameters of the tool, including the back angle.

Therefore, the professional tool grinding center must be equipped with the universal tool measuring instrument.But there are not many suppliers of this equipment, and there are German and French products in the market.

6, grinding technicians

The best equipment also needs personnel to operate, and the training of grinding technicians is naturally one of the most critical links.Because of the relatively backward manufacturing industry of the Chinese tool, coupled with the serious lack of vocational training, the training of tool grinding technicians can only be solved by the enterprise itself.

7, conclusion

With the hardware of grinding equipment, testing equipment and grinding standards, grinding technicians and other software, the grinding work of precision cutting tools can be started. Due to the complexity of tool application, the professional grinding center must timely repair the grinding scheme according to the failure form of the cutting tool, and track the use effect of the tool. A professional tool grinding center must also constantly summarize experience in order to make the cutting tool better and more specialized!

JDR Diamond Tools Co., Ltd. Address:Huangtang,Xiake,Jiangyin,Wuxi,Jiangsu,China

Tel:86-510-86531604?????????????Fax:86-510-86533978 Whatsapp:008613506163439

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