Thread is on a cylinder or cone surface, along with the same profile which is formed by the spiral tooth type continuous bump and groove and regulations.Among various kinds of machinery products, widely used with threaded parts.It is mainly used for connecting parts and fastening parts, transmission parts and components which are used for measuring and so on.In the numerical control lathe machining thread is one of the more commonly used processing methods.On CNC lathe processing thread with high machining precision and good product uniformity, wide range of processing advantages occupies more and more important status in the mechanical processing.This article embarks from the practical application, this paper expounds on the CNC lathe processing thread, because of equipment, tool or operator, in the process of cutting are prone to failure, as well as the solution.Along with the development of science and technology, numerical control lathe, the popularity on the nc lathe turning thread is used by more and more in the mechanical processing.Numerical control lathe in machining high precision, good product identity, range, convenient debugging (especially it can precision machining in the car difficult to machining parts) on the surface of some of the special advantages of occupies more and more important status in the mechanical processing.Thread on nc lathe turning common failures and solutions are: 1. 1 knife.1 the main reason (1) the tool rake Angle is too big, the X axis screw machine tool clearance;(2) the tool installation too high or too low;(3) the workpiece clamping rickety;(4) the cutting tool wear is too large;(5) the cutting dosage is too large.1.2 solution (1) reduce the tool rake Angle, the maintenance of machine tool adjustment screw clearance of X axis, the screw clearance self-compensation function of CNC lathe machine X axis screw clearance compensation;(2) tool installed too high or too low, too, are turning to a certain depth, knife surface to resist the workpiece after turning tool, increase the friction, even the workpiece bending, Mr. Knife phenomenon;Too low, the chip is not easy to discharge, turning the direction of the radial force is the workpiece center, plus a cross into the gap of lead screw and nut is too big, the depth of the turning automatically tend to deepen constantly, thus the workpiece is raised, a knife.At this point, should timely adjust the height of cutting tool, the blade and the axis of the workpiece contour (can use a tailstock to top knife).In coarse car and half car, point position is about 1% higher than the center of the workpiece D processed workpiece diameter (D).(3) the workpiece clamping not firm, the rigidity of workpiece itself cannot bear cutting when the cutting force, and thus produce excessive deflection, change the tool and workpiece center height (workpiece be inflated), forming cutting depth jump, a knife, at this time should be the workpiece clamping and firm, can use the tailstock top, etc., in order to increase rigidity workpiece.(4) the cutting tool wear is too big: caused by cutting force increases, the peak of bending workpiece, a knife.At this time should be grinding tool.(5) cutting dosage (mainly back turning and cutting speed) is too large, according to the workpiece size 5 lead and workpiece rigid choice of rational cutting parameter.2.Withholding 2.1 fault phenomenon when the screw turn a turn, artifacts not turned integer instead.2.2 main reasons for the machine tool spindle encoder synchronous drive belt wear, undetectable spindle synchronization real speed;Enter the host program is not correct;X or Y axis screw rod wear.2.Solution 3 (1) the main shaft encoder synchronous belt wear: due to the nc lathe turning thread, the movement of the tool and spindle relationship is by the machine tool host issued instructions to control the information processing center, thread cutting, the spindle speed is constant, X or Y axis can be according to the workpiece size and spindle speed lead to adjust speed, so the center must be detected real speed spindle synchronization, in order to make the right command control X or Y axis move correctly.If the system can’t detect the real speed of the spindle, the actual cutting off when different instructions to X or Y, then the spindle turn a turn, the cutting tool moving distance is not a lead, the second knife cutting thread will buckle.In this case, we only repair machine, replace the spindle synchronous belt.2) input of the program is not correct, when it in order to prevent disorderly thread cutting, must ensure that a knife after turning, its trajectory coincides with a knife before turning in the car we use reverse method to prevent disorderly buckle.On nc lathe, we use the program to prevent disorderly clasp, is when the machining program, we use the program control thread before turning a knife, the blade, make a knife after starting location with a knife before starting location overlap (equivalent to in the car turning thread, return to a previous knife the car out of the spiral groove), such a car out of the thread won’t buckle.Sometimes, due to program input lead incorrect (after a program with the lead a lead inconsistent), also can appear when turning disorderly phenomena.