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CNC Router Bits Guide

A CNC router bit is a rotary tool with one or more teeth for milling operations. When working, each cutter tooth cuts off the allowance of the workpiece intermittently in turn. CNC router bits are mainly used for machining planes, steps, grooves, forming surfaces and cutting workpieces on milling machines. We believe that when choosing a CNC router bit, pay attention to the CNC router bit body and tool holder:

1. Whether the CNC router bit is used by a CNC machining center or a common milling machine.

2. The material and hardness of the CNC router bit.

3. The specifications of the CNC router bit, such as: blade length, full length, blade diameter, shank diameter, etc.

If it is used on a CNC machining center, solid carbide should be used. White steel can be used for ordinary milling machines.

White steel CNC router bits are softer than carbide CNC router bits. High-speed steel knives are cheap and have good toughness, but their strength is not high, making them easy to cut, and their wear resistance and thermal hardness are relatively poor. For hard materials, if the coolant is not in place, it is easy to burn the knife, which is one of the reasons for the low thermal hardness.

Cemented carbide CNC router bits have good thermal hardness and wear resistance, but poor impact resistance. The blade will be broken if you drop it. Cemented carbide is a material made of powder metallurgy. Around 900-1000℃. Therefore, white steel is suitable for ordinary milling machines, and alloy CNC router bits are used in CNC machining centers.

Ⅰ. Selection of the diameter of the CNC router bit

The selection of the diameter of the CNC router bit varies greatly depending on the product and the production batch. The selection of the cutter diameter mainly depends on the specifications of the equipment and the processing size of the workpiece.

1. Plane CNC router bit

When choosing the diameter of the face CNC router bit, it is mainly necessary to consider that the power required by the tool should be within the power range of the machine tool, and the diameter of the machine tool spindle can also be used as the basis for selection. The diameter of the plane CNC router bit can be selected according to D=1.5d (d is the diameter of the spindle). In mass production, the tool diameter can also be selected according to 1.6 times the cutting width of the workpiece.

2. End mill

The selection of the diameter of the end mill should mainly consider the requirements of the processing size of the workpiece, and ensure that the power required by the tool is within the rated power range of the machine tool. If it is a small diameter end mill, the main consideration should be whether the maximum number of revolutions of the machine tool can reach the minimum cutting speed (60m/min) of the tool.

3. Slot CNC router bit

The diameter and width of the slot CNC router bit should be selected according to the size of the workpiece to be processed, and ensure that its cutting power is within the allowable power range of the machine tool.

Ⅱ. The choice of CNC router bit blade

For fine milling, ground inserts are preferred. This kind of insert has better dimensional accuracy, so the positioning accuracy of the cutting edge in milling is higher, and better machining accuracy and surface roughness can be obtained. In addition, the development trend of ground milling inserts for finishing is to grind out chip flutes to form large positive rake cutting edges, allowing the inserts to cut at small feeds and small depths of cut. For carbide inserts without sharp rake angles, when using small feed and small depth of cut, the tool tip will rub against the workpiece and the tool life will be short.

In some processing situations, it is more appropriate to use pressed blades, and sometimes it is necessary to choose ground blades. It is best to use pressed inserts for roughing, which can reduce processing costs. The dimensional accuracy and edge sharpness of the pressed blade are worse than those of the ground blade, but the edge strength of the pressed blade is better, it is resistant to impact during rough machining, and can withstand a large depth of cut and feed. The pressed inserts sometimes have chip grooves on the rake face, which can reduce the cutting force, and at the same time, reduce the friction with the workpiece and chips, and reduce the power demand.

However, the surface of the pressed blade is not as close as that of the ground blade, the dimensional accuracy is poor, and the height of each cutting edge on the CNC router bit body is quite different. Since pressed blades are cheap, they are widely used in production.

Ground high rake angle inserts for milling sticky materials such as stainless steel. Through the shearing action of the sharp edge, the friction between the blade and the workpiece material is reduced, and the chips can leave the front of the blade faster.

As an alternative combination, a pressed insert can be installed in the insert seat of most CNC router bits, followed by a ground doctor blade. Scraping blades remove roughing marks and achieve better surface roughness than pressing blades alone. Furthermore, the use of a doctor blade reduces cycle time and costs. Scraping technology is an advanced technology that has been widely used in the fields of turning, grooving and drilling.

Ⅲ. Selection of CNC router bit body

The price of CNC router bits is relatively expensive. The price of a face CNC router bit body with a diameter of 100mm may exceed 600 US dollars, so it should be selected carefully to meet the specific processing needs.

1. First of all, when choosing a CNC router bit, the number of teeth should be considered. For example, a coarse-tooth CNC router bit with a diameter of 100mm has only 6 teeth, while a fine-tooth CNC router bit with a diameter of 100mm can have 8 teeth. The size of the tooth pitch will determine the number of teeth that participate in cutting at the same time during milling, which affects the smoothness of cutting and the requirements for the cutting rate of the machine tool. Each CNC router bit manufacturer has its own line of coarse and fine face CNC router bits.

2. Coarse-tooth CNC router bits are mostly used for roughing because they have larger chip pockets. If the chip flute is not large enough, it will cause difficulty in chip rolling or increase the friction between the chip and the cutter body and the workpiece. At the same feed speed, the cutting load per tooth of the coarse-tooth CNC router bit is larger than that of the dense-tooth CNC router bit.

3. The cutting depth during fine milling is shallow, generally 0.25~0.64mm, the cutting load per tooth is small (about 0.05~0.15mm), and the required power is not large. You can choose a dense-tooth CNC router bit, and you can choose a larger feed rate. Since the metal removal rate is always limited in fine milling, it is okay to have a smaller chip flute for a fine-pitch CNC router bit.

4. For the spindle with larger taper hole size and better rigidity, the fine-tooth CNC router bit can also be used for rough milling. Since the dense-tooth CNC router bit has more teeth involved in cutting at the same time, when using a larger depth of cut (1.27 ~ 5mm), it is necessary to pay attention to whether the power and rigidity of the machine tool are sufficient, and whether the chip pocket of the CNC router bit is large enough. The chip removal needs to be verified by tests. If there is a problem with the chip removal, the cutting amount should be adjusted in time.

5. When performing heavy-duty rough milling, excessive cutting force can cause the machine tool with poor rigidity to vibrate. This chatter can lead to chipping of carbide inserts, reducing tool life. The choice of coarse-tooth CNC router bits can reduce the power requirements of the machine tool. Therefore, when the size of the spindle hole is small (such as R-8, 30#, 40# taper holes), the coarse-tooth CNC router bit can be used for milling effectively.

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