Troubled by internal hole turning? Complete inner hole processing in article

Internal hole turning, also known as boring, is the process of enlarging the inner hole of a workpiece or processing the inner surface of a hollow workpiece using turning methods. It can be processed using most of the outer circle turning techniques. Today we will explore common troubles in inner hole turning and provide some practical solutions to help you easily deal with them, making inner hole machining more effortless.

Problems in Turning Inner Holes

Problems in Turning Inner Holes

1) Vibrating knife

Long overhang is the main cause of knife and vibration problems. The inner hole turning tool is subjected to both radial and axial forces, which can cause the tool tip to deviate from the predetermined position, resulting in deformation of the tool holder. The longer the tool holder, the more obvious the deformation and vibration.

2) Poor surface quality

Poor chip removal may lead to poor surface quality of the workpiece. If iron chips cannot be removed from the inner hole according to the plan, they will squeeze and friction the inner wall of the workpiece, causing the turning of the inner hole to fail.

3) Blades are prone to breakage

Vibration and poor chip removal may cause blade breakage. During vibration and iron filings squeezing, the blade is prone to breakage.

Solution to the problem of inner hole turning

1) Basic principles

The general rule for inner hole machining is to minimize tool overhang and select the largest possible tool size in order to achieve the highest machining accuracy and stability.

2) From the perspective of tool application, factors to improve the quality of inner hole machining

The selection of blade groove type: The blade groove type has a decisive impact on the cutting process. Generally, for inner hole machining, a sharp cutting edge with high edge strength is selected as the front angle groove type blade.

Selection of tool main deviation angle: When selecting the main deviation angle, it is recommended to choose a main deviation angle as close as possible to 90 °, and not less than 75 °, otherwise it will cause a sharp increase in radial cutting force.

Selection of tool tip radius: In the inner hole turning process, the small tool tip radius should be the preferred choice. Increasing the tool tip radius will increase radial and tangential cutting forces, and also increase the risk of vibration trends. At the same time, while ensuring the minimum radial cutting tool, using the maximum tip radius can obtain a more robust cutting edge, better surface texture, and a more uniform pressure distribution on the cutting edge.

3) Effective discharge of chips

In the machining of inner holes, chip removal is also very important for the machining effect and safety performance, especially when machining deep holes and blind holes.

Short spiral chips are ideal chips for inner hole turning, which are easier to discharge and do not cause significant pressure on the cutting edge when chips break.

When the chips are too short during processing, the chip breaking effect is too strong, which will consume higher machine power and have a tendency to increase vibration.

However, if the chips are too long, it will make it more difficult to remove them. The centrifugal force will press the chips towards the hole wall, and the remaining chips will be squeezed onto the surface of the processed workpiece, which will pose a risk of chip blockage and damage to the tool.

Therefore, when performing inner hole turning, it is recommended to use tools with internal cooling. In this way, the cutting fluid will effectively discharge the chips from the hole.

4) Selection of tool clamping method

The clamping stability of the cutting tool and the stability of the workpiece are also very important in inner hole machining. They determine the magnitude of vibration during machining and whether this vibration will increase. It is very important for the clamping unit of the tool holder to meet the recommended length, surface roughness, and hardness.

The overall support is better than the tool holder directly clamped with screws. It is more suitable to clamp the tool holder onto the V-shaped block with screws, but it is not recommended to clamp the cylindrical handle tool holder directly with screws, as direct action of screws on the tool holder can damage the tool holder.

5) Effective elimination of vibration and increased iron filings by using special tool holders

Damping tool holder: This type of tool holder generally uses integral hard alloy as the tool body, which can effectively reduce tool vibration in the small hole field.

The characteristics of the damping blade:

Anti seismic tool holder: This type of tool holder generally has seismic elements inside the tool holder, which can effectively reduce vibration caused by excessive overhang. However, these seismic measures that start with cutting tools are often expensive and have harsh application scenarios.