Instructions for the use of cemented carbide boring tools!

For boring holes, especially small holes made with a solid alloy boring bar, you may experience the following conditions: the boring bar is adjusted at or slightly above the center line, the diameter of the boring bar is smaller than the hole diameter, the machining condition looks good, and the machining procedure is also checked correctly. After the adjustment is completed and satisfied, press the start button to start processing, and the coolant splashes around; nothing is observed before the boring bar is withdrawn from the part.

After boring, the worry becomes reality: the boring head is gone!

The reason for this is usually the accumulation of chips or the boring tool trying to penetrate the bottom of the blind hole. If it is found through inspection that the boring bar head is still in the hole and is difficult to remove, the possible cause is that the accumulation of chips in the hole causes this catastrophic failure. The reason for this is that cutting parameters such as cutting depth and feed rate are too large, resulting in material removal rate greater than chip removal ability. One of the solutions is to use a smaller diameter boring bar. If a smaller diameter boring bar cannot be used, the cutting parameters must be reduced to reduce the metal removal rate. If the inspection finds that the broken boring bar is Cemented Carbide Inserts not in the hole or is loose in the hole and it is difficult to take out, the possible reason is that the boring depth is greater than the depth of the existing hole on the part, causing the boring bar to break. At this time, remember that the boring tool cannot drill holes like a drill.

 

The cause of the flank wear of the boring tool was wrongly judged

Tool wear

When the boring tool is adjusted correctly and no catastrophic machining failure occurs, the low production efficiency caused by frequent tool changes is unacceptable. Examination found that the flank of the cutting edge of the tool was excessively worn. However, excessive or rapid wear of the flank can be misdiagnosed. Usually, excessive cutting time, intermittent cutting or cutting vibration will cause chipping SNMG Insert at the cutting edge, which is regarded as flank wear. Flank wear may be caused by the built-up edge on the rake surface first. This is because the cutting heat and cutting pressure weld the chips to the tool's rake surface to form a built-up edge. At a certain moment of cutting, the chips will be Take away the built-up edge and at the same time take away the alloy material on the rake face of the tool.

When the chips take away the built-up edge and the alloy material on the tool, the built-up edge can be misdiagnosed as flank wear

In order to determine the real cause of the flank wear, you can check whether there is a built-up edge or chipping after one or two holes are processed by the boring tool.

Reducing cutting pressure and cutting heat can reduce built-up edge. Cutting pressure is related to depth of cut and feed speed. Reducing the depth of cut and the feed rate can reduce the cutting pressure and cutting heat, but at the same time it will also reduce the production efficiency. One way to improve production efficiency is to use coated tools. When the chip flow passes through the cutting surface of the tool, the coating can reduce the cutting heat. The PVD film coating of AlTiN is more effective than the CVD film coating, because too thick the coating will deteriorate the cutting performance of the cutting edge.

Carbide boring tool

Cutting cooling

Coolant is usually used to reduce cutting heat. This is simple and easy for turning the outer circle, but it is very difficult for boring the inner hole, because there are boring bars and chips that need to be cooled in the hole when boring. The coolant nozzle placed close to the orifice will hinder cutting. Therefore, the method is to provide internal coolant through the boring bar. It is an ideal solution to provide sufficient flow of coolant along the circumferential direction of the boring bar. The resistance of the coolant is small and the bottom of the bored hole can be reached, which usually requires multiple locations. Place coolant nozzles, such as on the main flank, rake face and secondary flank.

If edge chipping occurs after machining several parts, the possible cause is intermittent cutting, such as cross holes or keyways. In this case, it is necessary to choose a tool with a strengthened cutting edge.

If chipping is not caused by interrupted cutting, cutting vibration may be the cause. Like intermittent cutting, cutting vibration will cause the tool to bend downward under force, and then rebound when the force disappears, thereby causing an impact on the cutting edge of the tool. One possible solution is to increase the feed rate. The feed rate is increased by 10%, which can sufficiently increase the cutting pressure to keep the tool under pressure to avoid the impact of springback on the cutting edge.

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