The lathe is aimed at the so-called plane thread, which is the thread machined on the end face of a cylinder or a disc. The trajectory of the turning tool relative to the workpiece is an Archimedes spiral, which is different from the commonly processed cylindrical thread. Turning plane threads on an ordinary lathe generally uses a smooth rod drive to rotate the middle carriage screw and drive the middle carriage of the lathe to move the tool horizontally to turn. This requires that for each revolution of the workpiece, the middle carriage moves one thread pitch on the workpiece laterally. When the workpiece thread pitch is not strict, the thread pitch of the workpiece plane thread can be divided by the multiple of the increased thread pitch of the lathe, and the obtained quotient is used to select the approximate horizontal feed amount, and the handle of the tool box is pulled as required, and then Turn the increase-pitch handle on the headstock to the increased pitch position, and turn the speed-change handle on the headstock to the required position. After installing the tool, you can turn the plane thread. When the workpiece pitch is strictly required, it is necessary to replace the hanging wheel box and hanging wheel. Before calculating the change gear, according to the above method, select an approximate amount of horizontal knife, and pull the knife into the box, increase the pitch and the shift handle, and carry out the horizontal knife. Then use the integer of the main axis to divide the distance moved by the horizontal carriage, which is the actual pitch. Under normal circumstances, the pitch will not be equal to the required thread pitch of the workpiece, so it is necessary to calculate and replace the hanging wheel of the hanging wheel box.
When turning, it is best to use an elastic tool holder. The geometric parameters of the tool head are the same as those of cylindrical threads, but the secondary relief angle on the inner circle side of the tool head must be ground to prevent this part from getting in the way during turning. Adopt the spindle to turn the tool forward and backward and make the tool return. There are two ways to eat a knife: one is to use a small knife holder to eat and retract the knife, and the small thousand-centimeter hoop is used to count; the other is to install a magnetic meter stand and a dial indicator on the large guide rail in front of the large carriage to control the large drag. The position of the board and the amount of knives, and use a large carriage to grab and retract the knives.
In the process of turning plane threads, in addition to square threads, turning threads of other tooth shapes also needs to “drive” like turning cylindrical threads to fine-turn the two sides of the tooth shape.
There are also two methods for “driving the knife”: one is to use a large carriage to eat and retract the knife, rotate the small knife holder 90° counterclockwise and fix it, and shake the handle of the small knife holder when “driving the knife”; the other is to use When the large carriage or small tool holder eats and retracts the tool, when you want to “catch the tool”, put the tool head outside the workpiece, and stop the spindle during the tool movement, but there must be no reverse rotation. At this time, the worm handle will fall off. , Rotate the handle of the middle carriage to the value required to “catch the knife”, and then lift off the worm handle. To use this method to “drive the knife”, you must eliminate the gap in the transmission chain, that is, which direction you need to “drive the knife”, and the carriage in the lathe must move the knife in the same direction.