The profile angle of metric trapezoidal thread is 30°, and the pitch is 1.5 to 8mm. In theory, standard carbide trapezoidal thread inserts can be purchased and turned.
For large-pitch trapezoidal threads with a pitch exceeding 8 mm, since there is no standard carbide trapezoidal thread insert, forming tools are still used so far. The surface quality of the car will also not be very good. Since the cutting linear speed cannot be too high, the processing efficiency will not be high.
There is a principle for using CNC lathe tools: standard turning tools including standard blades should be used as much as possible. Don't use forming tools unless absolutely necessary.
I choose a standard ordinary turning insert with an included angle of 35 degrees, and the thread angle of the metric trapezoidal thread is 30 degrees. On the surface, it seems unusable, but in reality it is not. Please see how I handle it.
1. An example of a trapezoidal thread with a pitch of 10mm
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2. Standard cutter body and standard blade used
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3. Three knives are installed on the knife holder
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4. Use the T1 cutting edge to advance at 17.5 degrees and divide it into 20 rough turnings.
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5. Use T2 tool to finish turning the left wall and bottom surface of the groove
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6. Use T3 tool to finish turning the right wall and right bottom of the groove
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7. Main program in processing program
O520
#101=100; (#1 represents the outer diameter of the trapezoidal thread)
#102=100; (#2 represents the length of the trapezoidal thread, 150 is used for processing)
#103=10; (#3 represents the trapezoidal thread pitch P)
#104=0.5; (#4 represents the top clearance of the trapezoidal thread, which can be found in the standard)
#105=25; (#5 represents the length of the speed-up section when turning this thread, which can be increased/decreased)
#106=0.4; (#6 represents the tool nose radius used when finishing this thread, P2~P5 uses 0.2, P6~P12 uses 0.4, P14~P44 uses 0.8)
#107=20; (#7 represents the number of rough turning tools with a 35-degree centering tool, which can be increased/decreased)
#108=0.15; (#8 means using a 35-degree centering knife to tilt left and right to finely turn the left and right wall X to the depth of each knife, which can be increased/decreased)
#109=0202; (#9 represents the tool position and tool compensation number of the tool used for the left wall and left half bottom surface of finishing turning, which should be followed by the actual command)
#111=0303; (#11 represents the tool position and tool compensation number of the tool for finishing the right wall and right half bottom surface, which should be followed by the actual command)
#113=5; (#13 represents the number of cutting tools for the left half bottom surface and the right half bottom surface of finishing turning, which can be increased/decreased)
G54 S300 M03; (S360 for processing, can increase/decrease; M03 for right-hand thread/M04 for left-hand thread)
T0101; (The tool position number and tool compensation number of the centering tool for rough turning should be determined by the actual command)
G00 X145 Z100; (The X command value and Z command value of the starting position are determined according to the size of the machine tool and workpiece)
G65 P530 A#101 B#102 C#103 I#104 J#5 K#6 D#7 E#8 F#9 H#11 M#13; (Call the O530 subroutine and assign values to 11 variables in it )
G00 X145 Z100 M05; (The X command value and Z command value of the return position are determined according to the size of the machine tool and workpiece)
M30;
Note: As long as the 11 variables in the main program are correctly assigned, processing can be performed.
8. Advantages of using standard ordinary cylindrical turning tools to turn trapezoidal threads
A. For metric trapezoidal threads with pitch P exceeding 8mm
1) There is no need to make forming turning tools made of high-speed steel or carbide;
2) If a forming turning tool is used, the accuracy of the profile contour depends on the accuracy of the forming turning tool (during processing
cannot be adjusted), and the contour turned with a standard ordinary cylindrical turning tool is "walked", so
With high cross-section contour accuracy;
3) If you use a forming turning tool, due to the large contact surface, the surface quality of the thread will not be very good.
When using standard ordinary cylindrical turning tools, the contact surface of each tool is very small, and the linear speed can be increased.
Therefore, the surface quality of the car is good;
4) Using standard ordinary cylindrical turning tools to turn trapezoidal threads requires relatively low skill requirements for operators.
B. For metric trapezoidal threads with pitch P not exceeding 8mm
1) If you use a standard metric trapezoidal thread insert for turning, you must first purchase this insert and the corresponding cutter body;
2) If a standard metric trapezoidal thread insert is used, since it is still a forming knife in essence, the thread
The surface quality of the grain is also not easy to control;
3) If you make your own forming turning tool, the situation is the same as described in "A" above.
