Threaded parts are widely used in mechanical products. The CNC machining technology of thread includes CNC turning, CNC milling and tapping machining and so on.
CNC turning thread is actually CNC lathe machining thread.
How to Machining Thread with CNC Lathe?
There are generally 4 methods for machining threads on CNC lathes: straight-forward method, oblique method, left and right cutting method and rough grooving method with grooving knife.
So next, let’s take a look at the specific operations of these four methods of machining threads on CNC lathes.
Straight forward method
The straight-feed method refers to the intermittent feeding of the thread cutter into the depth of the tooth. When using this method to process trapezoidal threads, the three sides of the thread turning tool are involved in cutting, resulting in difficulty in chip removal, increased cutting force and cutting heat, severe tool tip wear, and excessive tool feed may also cause knife sticking. Obviously, it is not advisable to process large-pitch trapezoidal threads and worms.
The thread turning tool is fed obliquely and intermittently to the depth of the tooth along the direction of the tooth profile angle. When using this method to process trapezoidal threads, only one side of the thread turning tool is always involved in cutting, so that the chip removal is smoother, the force and heat of the tool tip are improved, and it is not easy to cause knife sticking during turning.
left and right cutting method
The thread turning tool is fed to the depth of the tooth in a staggered gap along the direction of the tooth profile angle. This method is the same as the oblique method, and it is realized by macro program programming on the CNC lathe.
Grooving knife rough grooving method
This method first uses a grooving knife to cut the groove roughly, and then uses a trapezoidal thread turning tool to process both sides of the thread. This method is difficult to achieve in CNC lathes.
In addition to several common thread processing methods, we also introduce the characteristics and processing methods of worm and large-pitch trapezoidal threads:
Turning worm and large lead thread, no matter using oblique method or left and right cutting method, the cutting resistance is very large. In the past, high-speed steel turning tools could only be used for low-speed turning, and the production efficiency was very low. In order to process with cemented carbide tools, it is necessary to try to reduce the cutting depth of the blade, so the “layered cutting” method is used for processing.
Divide the tooth groove of thread or worm into several layers, and convert it into several shallow trapezoidal grooves for cutting. The cutting of each layer adopts the turning method of going straight first and then turning to the left. Since the groove depth does not change when cutting left, the tool only needs to move to the left! Feed along the direction of the guide rail. In this way, the left and right cutting method and the oblique cutting method are organically combined. Since there is only one cutting edge for cutting, the cutting allowance can be effectively controlled, so that the surface quality and the service life of the tool can be well guaranteed.
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