How to Choose a Turning Tool for Finishing Turning Processing?
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How to Choose a Turning Tool for Finishing Turning Processing?
In turning processing, especially for finishing, how to choose a turning tool?
- Determine the entering angle of the turning tool holder
Among the entering angles of conventional tools, those suitable for finishing are generally between 90° and 95°, especially 91°, 93°, and 95°. The entering angle close to 90° makes the cutting force follow the axis of the workpiece, and no vertical force is applied to the workpiece to avoid vibration and deformation (thin-walled parts processing is especially important). The entering angle is generally guaranteed on the tool bar.
- Determine the angle of the tool tip, or choose the shape of the tool
Generally, the commonly used turning insert forms are:
Round insert (start with R, ISO standard code, the same below), 90 degree square insert (start with S), 80 diamond insert (start with C), 80 degree convex triangle insert (start with W), 60 degree triangle insert (start with T), 55 degree diamond insert (beginning with D), 35 degree diamond insert (beginning with V).
These tool shapes basically cover more than 90% of conventional turning inserts. These types of inserts are arranged in terms of tool strength: R, S, C (W), D, V. R insert has the highest strength and V has the lowest. But the higher the strength, the greater the resistance and the greater the risk of vibration. Therefore, we often choose R, S, C (W) for roughing. For finishing, we will choose D and V. The profiling ability required for finishing is also V the best and R the worst.
- Determine the rake angle and rear angle of the tool
The negative rake angle tool has good rigidity and is not easy to chip, which is suitable for rough machining, while the positive rake angle insert cuts lightly and is more suitable for finishing. There is a matching relationship between the rear angle and the rake angle. Generally, the negative rake angle inserts are basically 0 degrees. The positive rake angle insert has 5°(B, ISO code, the same below), 7°(C), 11°(P) three commonly used clearance angle combinations (referring to turning only).
Common combinations:
CC/CP (C type positive rake angle insert 7°/11° clearance angle), DC (D type positive rake angle insert 7° clearance angle), VC/VB (V type positive rake angle insert 7°/5° clearance angle ), WB/WC (W-type positive rake angle insert 5°/7° clearance angle), these combinations are also the insert shapes used in conventional finishing (the front and rear corners are determined)
Combining the three, the tool form for conventional finishing is as follows:
95° entering angle tool holder + CC insert
93° entering angle tool holder + WB/WC/DC/VC/VB insert
91° entering angle tool holder + DC/VC/VB insert
Among them, the 93° entering angle toolholder +DC is the best finishing plan recommended by individuals (referring to the turning radial direction only). This plan is equipped with appropriate cutting parameters and the processing effect should be one of the best in current turning. I have tried 1.6 roughness of several different materials, and 0.8 roughness of another steel part is because of the inner hole and the diameter of the shank is limited, so I can only use 95° entering angle shank + CC insert.
Of course, the above options are not unique. In the working condition where the medium and large diameter solid materials can reach high linear speed, the insert with 0° clearance angle (ISO code N) can also produce better roughness, but the roughness at this time is more dependent on thick oxidation aluminum CVD coated inserts are “ground” at high linear speeds. This roughness is basically about one grade different from the roughness processed by the tool selected above. In other words, the CN insert can be turned to 1.6, and the DC insert can be turned to 0.8.
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