Boring refers to the further processing of forged, cast or drilled holes. Boring can enlarge the hole diameter, improve the accuracy, reduce the surface roughness and correct the deviation of the original hole axis. Boring can be divided into rough boring, semi precision boring and fine boring.
Boring is divided into general boring and deep hole boring. General boring can be done on ordinary lathe, and the boring cutter can be fixed on lathe tailstock or small tool holder. Deep hole boring requires a special deep hole drilling and boring machine, boring tool should be added with boring stem, and hydraulic pump station should be added to remove iron filings with coolant.
Boring steps and precautions
Boring tool installation
It is very important to install the boring tool working part, especially for the work adjustment based on the eccentric principle. After installing the boring tool, it is necessary to observe whether the upper plane of the main cutting edge of the boring tool is in the same horizontal plane with the feed direction of the boring head? Only when they are installed on the same horizontal plane can several cutting edges be ensured to be in normal cutting angle.
Trial boring with boring cutter
The boring cutter shall be adjusted according to the process manufacturing requirements, and the allowance of 0.3 ~ 0.5mm shall be reserved. The rough boring allowance shall be less than or equal to 0.5mm according to the initial hole allowance for expanding boring and matching boring. The machining allowance for subsequent fine boring must be met.
After the boring tool is installed and loaned, trial boring is needed to verify whether the boring tool debugging meets the requirements of rough boring.
Boring requirements
Before boring, carefully check whether the tooling, positioning datum of workpiece and positioning elements are stable and reliable.
What is the diameter of the initial hole to be machined by caliper? How much machining allowance do you still have?
Before boring, check whether the repeated positioning accuracy and dynamic balance accuracy of the equipment (spindle) meet the requirements of processing and manufacturing.
During the trial boring process of horizontal plus boring, the dynamic runout value of the boring bar gravity suspension must be checked, and the cutting parameters should be modified reasonably to reduce the influence of centrifugal shear vibration.
According to the steps of rough boring, semi precision boring and fine boring, the layer boring allowance should be reasonably distributed, and the rough boring allowance should be about 0.5mm; the semi precision boring and fine boring allowance should be about 0.15mm, so as to avoid the tool shifting phenomenon caused by excessive allowance in semi precision boring and affect the precision of fine boring allowance adjustment.
For difficult to machine materials and high-precision boring (tolerance ≤ 0.02mm), fine boring processing steps can be added, and boring allowance should not be less than 0.05mm to avoid elastic tool yielding of machining surface.
In the process of boring tool setting, attention must be paid to avoid the impact between the boring tool working part (blade and cutter seat) and the tool block, damaging the guide groove of the blade and the cutter base, causing the change of the boring cutter adjustment value and affecting the hole diameter processing accuracy.
During boring process, pay attention to keep enough cooling, increase the lubrication effect of the machining parts, so as to reduce the cutting force.
The chip removal is strictly carried out in each machining step to prevent the chip from participating in the secondary cutting and affect the machining accuracy and surface quality of the hole.
During the boring process, the wear degree of the cutting tool (blade) should be checked at any time and replaced in time to ensure the quality of the hole diameter processing; the blade must not be replaced in the precision boring step to prevent errors; after each step of processing, the process quality control requirements must be strictly implemented, and the actual processing hole diameter should be carefully detected and recorded to facilitate analysis, adjustment and improvement of boring process.