Basic Concepts of Boring and Boring Tools

Fig. 1 Schematic diagram of boring cylindrical holes

Figure 2 Double-edged boring tool

Figure 3 Modular Boring Tools

boring

Boring is a type of cutting where a rotating single-edged boring tool is used to enlarge a pre-made hole in a workpiece to a specific size in order to achieve the required accuracy and surface roughness. Boring operations are usually carried out on boring machines, machining centres and combined machine tools, the main role of which is to process boxes, brackets and machine seats and other workpieces such as cylindrical holes, threaded holes, grooves in the holes and the end face; if the use of special attachments, boring can also be processed inside and outside of the spherical, tapered holes and so on. For steel materials, the accuracy achieved when boring is usually in the range of IT9 to 7, with a surface roughness of Ra2.5 to 0.16µm.

When boring, the workpiece is mounted on the machine table or machine fixture, the boring tool is clamped to the boring bar (can also be made with the boring bar as a whole), driven by the spindle to rotate. When the use of the boring mould, the boring bar and spindle was floating connection, machining accuracy depends on the accuracy of the boring mould; do not use the boring mould, the boring bar and the spindle for the rigid connection, machining accuracy depends on the accuracy of the machine tool. In view of the large overhanging distance of the boring bar, easy to vibrate, the selectedCutting volumeNot for very large. Boring process includes rough boring, semi-fine boring and fine boring. The cutting speed of HSS cutter head is generally 20 to 50m/min, while the cutting speed of carbide cutter head can reach 40 to 60m/min for rough boring and more than 150m/min for fine boring.

Precision boring, which requires very high precision and surface roughness, usually uses diamond boring machines and tools made of super-hard materials such as cemented carbide, diamond and cubic boron nitride, with very small feeds, i.e., 0.02 to 0.08 millimetres per revolution, and depths of cut of 0.05 to 0.1 millimetres, with cutting speeds higher than those of normal boring. Precision boring has a machining accuracy of IT7 to 6 and a surface roughness of Ra0.63 to 0.08 microns. Prior to precision boring, the precast hole is rough bored, semi-finished and finished, leaving a particularly thin and uniform machining allowance for precision boring. Boring tools.

There exists a kind of tool, it has a cutting part or two cutting parts, is specially used for the existing hole roughing, or semi-finishing, or to do finishing, this tool is the boring tool, boring tool can be used in the boring machine, but also in the lathe and by the machine tool is used for milling machine, due to the clamping method is not the same, the boring tool of the shank has a variety of forms, such as the square shank, there are also Morse taper shanks, and 7:24 taper shanks, to name a few.

The shape of the cutting part of the single-edged boring tool is similar to that of the lathe tool, in order to let the hole have high dimensional accuracy, the size of the boring tool for finishing has to be adjusted accurately, the fine-tuning boring tool can be used to accurately adjust the size of the boring hole on the machine tool, which has a precision vernier scaled indicator disc, the indicator disc and the heart of the bar equipped with the boring tool head constitute a pair of precision screw nut sub-agency, the nut is rotated, the heart of the bar equipped with the head of the tool can be moved in a straight line along the directional key, and the precision of the readings by means of the vernier scale can be as much as 0.001mm, the boring tool size can also be pre-adjusted outside the machine tool using the tool setter.

Double-Edge Boring Tools have two teeth, distributed on both sides of the centre, cutting at the same time, due to the radial force generated during cutting, balanced with each other, so you can increase the amount of cutting, productivity is quite high. Double Edge Boring Tools, according to the insert in the boring bar floating or not, divided into floating boring tools and fixed boring tools. Floating boring inserts are suitable for finishing holes. It is virtually equivalent to a reamer in that it produces holes with high dimensional accuracy and a clean surface, but it does not correct for deviations in hole straightness. To increase the number of resharpening cycles, floating boring tools are often made in an adjustable configuration.

In order to adapt to the various colours of the hole diameter and depth of the hole, and to reduce the variety of specifications of the boring tool, people design the boring bar and cutter head into a series of basic parts is the module. When used according to the needs of the workpiece to choose the appropriate module, put together a variety of boring tools, and thus simplify the design and manufacture of tools.