Basic Knowledge, Usage Methods, Installation Steps of Boring Tools
1. Basic Knowledge of Boring Tools
A boring tool is a type of boring cutting tool, usually with a round shank; square tool bars can also be used for larger workpieces. Its most common applications include internal hole machining, hole expansion, profiling, etc. It has one or two cutting parts and is specially used for rough machining, semi-finish machining or finish machining of existing holes. Boring tools can be used on boring machines, lathes or milling machines.
According to different clamping methods, there are various types of boring tools, including square shank, Morse taper shank and 7:24 taper shank. The shape of the cutting part of a single-edged boring tool is similar to that of a turning tool. To obtain high dimensional accuracy of the hole, the size of the boring tool for finish machining needs to be accurately adjusted. The fine-tuning boring tool can accurately adjust the boring size on the machine tool. It is equipped with an indicator dial with precise vernier scale. The indicator dial and the mandrel with the boring head form a pair of precision lead screw nut pair mechanism. When the nut is rotated, the mandrel with the tool head can move linearly along the guide key, and the reading accuracy can reach 0.001 mm with the help of the vernier scale. The size of the boring tool can also be pre-adjusted with a tool setter outside the machine tool.
A double-edged boring tool has two cutting teeth distributed on both sides of the center for simultaneous cutting. The radial forces generated during cutting balance each other, which can increase the cutting parameters and improve production efficiency. According to whether the insert floats on the boring bar, double-edged boring tools are divided into floating boring tools and fixed boring tools. Floating boring tools are suitable for finish machining of holes. They are actually equivalent to reamers and can bore holes with high dimensional accuracy and smooth surface, but cannot correct the linear deviation of the holes. To increase the number of regrinds, floating boring tools are often made into adjustable structures.
To meet the needs of various hole diameters and depths and reduce the variety and specifications of boring tools, people design boring bars and tool heads into serialized basic parts-modules. When in use, appropriate modules can be selected according to the workpiece requirements to assemble various boring tools, which simplifies the design and manufacturing process of the tools.
2. Usage Methods of Boring Tools
1. Special attention should be paid to cleanliness when installing the tool. Whether the boring tool is used for rough machining or finish machining, cleanliness must be guaranteed in all links of installation and assembly; the assembly of the tool shank and the machine tool, the replacement of the insert, etc., must be wiped clean before proceeding, and must not be careless.
2. The tool needs to be pre-adjusted, and its dimensional accuracy and intact state must meet the processing requirements. Except for single-edged boring tools, indexable boring tools generally do not adopt the method of manual trial cutting, so pre-adjustment before processing is particularly important. The pre-adjusted size must be accurate, adjusted to the middle and lower limit of the tolerance, and corrected and compensated considering the temperature factor; the tool pre-adjustment can be completed on a special pre-adjuster, on-machine tool setter or other measuring instruments.
3. Dynamic runout inspection must be carried out after the tool is installed. Dynamic runout inspection is a comprehensive indicator that reflects the accuracy of the machine tool spindle, the accuracy of the tool and the connection accuracy between the tool and the machine tool. If this accuracy exceeds 1/2 or 2/3 of the required accuracy of the processed hole, processing cannot be carried out. The cause must be found out and eliminated before processing can be started. The operator must keep this in mind and strictly implement it, otherwise the processed hole will not meet the requirements.
4. The service life of each part of the tool must be determined through statistical or detection methods to ensure the reliability of processing accuracy. For single-edged boring tools, this requirement can be appropriately lowered, but it is particularly important for multi-edged boring tools. The processing characteristic of indexable boring tools is pre-adjusting the tool and achieving the requirement in one processing. It is necessary to ensure that the tool is not damaged, otherwise unnecessary accidents will occur.
3. Installation Steps of Boring Tools
1. Connect the tool bridge to the tool shank with bolt 1.
2. Install the fine boring tool holder on the tool bridge.
3. Install the counterweight on the sliding body.
4. Tool adjustment:
1) Loosen the locking screw;
2) Roughly adjust the tool holder according to the scale line, so that the tool tip size is about 0.5 mm smaller than the size to be processed (Note: Ensure the rough adjustment size by comprehensively adjusting the fine boring tool holder and the dial);
3) Tighten the locking screw, and turn the adjustment screw on the fine boring tool holder to push against the rod part of the locking screw to prevent tool retraction.
5. Adjust the counterweight in the same way to achieve dynamic balance.
6. Lock the locking screw, perform trial boring, measure the size of the processed hole, compare it with the required size, and calculate the small deviation value.
7. Loosen the locking screw, rotate the dial (each small grid of the dial represents a diameter cutting depth change of 0.01 mm), so that the movement amount reaches the calculated small deviation value.
8. Lock the screw and process the workpiece to the specified size.
Installation Notes:
1. Pay attention to the adjustment of the fine boring tool head, do not use excessive force (do not rotate the dial beyond the range);
2. Do not disassemble the parts sealed with red paint, otherwise the fine-tuning device will be damaged;
3. Perform regular maintenance and add lubricating oil.
