How to choose the tool in turning?
Today, let's learn how to choose a tool in machining. What are the skills? Let's learn together.
First, determine the tool's lead angle
Among the leading angles of conventional tools, the finishing is generally between 90° and 95°, especially 91°, 93° and 95°. The principal declination close to 90° causes the cutting force to follow the axis of the workpiece, and does not apply a vertical force to the workpiece to avoid vibration and deformation (thin-wall machining is especially important). The lead angle is generally guaranteed on the arbor.
Second, determine the angle of the tool tip, select the shape of the tool in general, the commonly used blade forms are:
Round insert (starting with R), 90 degree square insert (starting with S), 80 diamond insert (starting with C), 80 degree convex triangular insert (starting with W), 60 degree triangular insert (starting with T), 55 degree diamond insert (starting with D) ), 35 degree diamond blade (starting with V).
These tool shapes cover more than 90% of conventional turning inserts. These blades are arranged in terms of tool strength: R, S, C (W), D, V. The R blade has the highest strength and the lowest V. However, the higher the strength, the greater the resistance caused, and the greater the risk of vibration. Therefore, we often use R, S, C (W) for roughing. For finishing, we will choose D, V. The profiling ability required for finishing is also V-optimal and R is the worst.
Third, determine the tool front angle back angle.
The negative rake angle tool has good rigidity and is not easy to be chipped, which is suitable for rough machining, while the positive rake angle cutting blade is light and more suitable for finishing. There is a matching relationship between the back angle and the front corner. Generally, the negative rake angle blades are basically 0 degree back angle. The positive rake inserts are available in 5° (B), 7° (C), and 11° (P) corners (only for turning).
CC/CP (C-type positive rake blade 7°/11° back angle), DC (D-type positive rake blade 7° back angle), VC/VB (V-type positive rake blade 7°/5° relief angle) ), WB/WC (W-type positive rake blade 5°/7° back angle), these combinations are also the shape of the blade used for conventional finishing (the corner angles of the front and rear corners are determined)
The combination of the three results, the form of conventional finishing tools are as follows:
95° lead angle cutter + CC blade
93° lead angle cutter + WB/WC/DC/VC/VB blade
91° lead angle cutter + DC/VC/VB blade
Among them, the 93° lead angle cutter + DC is the best recommended finishing scheme (only for turning radial). This scheme is equipped with suitable cutting parameters, and the machining effect should be one of the best in current turning. I have tried 1.6 roughness of several different materials. The 0.8 roughness of the other steel is limited by the inner hole and the diameter of the arbor. Only the 95° main angle arbor + CC blade can be used.
Of course, the above choice is not unique. Under the condition that the medium and large diameter solid materials can reach high line speed, the blade with 0° back angle (ISO code N) can also drive better roughness, but the roughness at this time is more by thick oxidation. Aluminum CVD coated blades are "grinded" at high line speeds. This roughness is almost the same as the roughness of the tool selected above. In other words, with the CN blade can drive to 1.6, I can use the DC blade to drive to 0.8.
The commonly used inserts in the inner hole finishing machine are also TC/TP (T-type positive rake insert 7°/11° back angle), the corresponding cutter rod combination 91° main declination cutter rod + TC/TP insert, inner hole diameter More than 16 fine cars, you can basically use DC blades, but DC has 07 and 11, 07 blades can process 16 ~ 20 inner holes, 25 and above can use DC11 blades. For fine cars with inner holes of 10 to 16 or so, CC blades or TC/TP blades can be used. If the inner hole is less than 10, generally only the CC blade is suitable, and the Japanese has a CC blade capable of 5.5 to 6 mm.