Tools for inner hole machining
According to different situations, inner hole turning tools can be divided into through hole turning tools and blind hole turning tools.
1. Through hole turning tool: in order to reduce the radial cutting force and prevent vibration, the main deflection angle of the through hole turning tool is generally 60-75 degrees, and the auxiliary deflection angle is 15-30 degrees. In order to prevent the friction between the back face of the inner hole turning tool and the hole wall and not to grind the back corner too much, it is generally ground into two back corners.
2. Blind hole turning tool: the blind hole turning tool is used to turn blind holes or step holes. The main deflection angle is 90-93 degrees. The tool tip is at the front end of the tool bar, and the distance between the tool tip and the outer end of the tool bar is less than the radius of the inner hole.
Inner hole processing technology
Turning hole is one of the commonly used hole machining methods, which can be used for rough machining and fine machining. In order to increase the rigidity of turning and prevent vibration, it is necessary to choose a thick tool bar as far as possible. When clamping, the extension length of the tool bar should be as short as possible, as long as it is slightly greater than the hole depth. The tool tip should be aligned with the center of the workpiece, and the tool bar should be parallel to the axis line. In order to ensure safety, use the inner hole knife to try it out before turning the hole. When finishing turning the inner hole, the blade should be kept sharp, otherwise it is easy to produce the taper of the turning distance of the knife and the hole.
Measuring tool for inner hole vehicle
When the accuracy requirements of aperture size are low, steel ruler, internal caliper or vernier caliper can be used for measurement. When the accuracy requirements are high, inner micrometer or inner diameter gauge can be used for measurement, and plug gauge can also be used for measurement of standard hole.
1. Vernier caliper: when measuring the aperture size with vernier caliper, pay attention to that the ruler body is parallel to the end face of the workpiece, and the movable measuring claw swings along the circumference to find the maximum position.
2. Inner micrometer: the direction of the scale line of this micrometer is opposite to that of the outer micrometer. When the differential cylinder rotates clockwise, the movable claw moves to the right and the measurement value increases.
3. Inner diameter dial gauge: the inner diameter dial gauge is formed by clamping the dial gauge on the measuring frame. Before measurement, replace the fixed measuring head according to the aperture size of the measured workpiece, and align the inner diameter dial gauge with the micrometer to the "zero" position. The minimum value of the swinging dial gauge is the actual size of the aperture.
4. Plug gauge: it is composed of a through end and a stop end. The through end is made according to the minimum limit size of the hole. It should be inserted into the hole during measurement, and the stop end is made according to the maximum limit size of the hole. It is not allowed to be inserted into the hole during measurement. When the same end can be inserted into the hole, but the stop end cannot be inserted, the hole size is qualified.
Analysis of machining quality of inner hole
1. The dimensional accuracy of the inner hole is out of tolerance: it is mainly caused by the lack of careful measurement or the wrong measurement method.
2. Hole taper: it may be caused by improper selection of cutting parameters, worn turning tools, insufficient sharpness of blade, and poor rigidity of tool bar
The lathe spindle axis is skewed, and the serious wear of the bed guide rail is also the reason for the taper of the machined hole.
3. The hole surface roughness is out of tolerance: it may be due to the improper selection of cutting parameters, resulting in chip buildup; Or the turning tool is worn, the blade is not sharp enough, and the tool bar vibrates during cutting.