The definition and processing points of "tapping" in CNC machining


Key points

1) The hole of the threaded bottom hole of the workpiece is chamfered, and both ends of the through hole thread are chamfered.

2) The position of the workpiece clamp should be correct. Try to make the center line of the threaded hole horizontal or vertical, so that the tapping is easy to judge whether the tap axis is perpendicular to the plane of the workpiece.

3) At the beginning of tapping, try to put the tap straight, then apply pressure to the tap and turn the twister. When cutting into 1-2 turns, carefully check and correct the position of the tap. Generally, when cutting 3-4 turns of thread, the tap position should be correct. In the future, it is only necessary to turn the gripper and not to apply pressure to the tap, otherwise the thread profile will be damaged.

4) When tapping, every time 1/2-1 turns of the twister is turned, about 1/2 turn should be reversed, so that the chips can be easily discharged after being broken, and the cutting edge can be reduced due to the chipping of the cutting edge.

5) When encountering a tapped hole, always exit the tap and remove the chips from the hole.

6) When tapping the screw hole of plastic material, lubricate the coolant. For steel materials, oil or a large concentration of emulsion is generally required, and higher edible vegetable oil or molybdenum disulfide is required. For stainless steel, oil No. 30 or vulcanized oil can be used.

7) When replacing a tap in the tapping process, first screw it into the tapped thread first, until it can no longer be screwed in, then use the twister to turn it. When the end cone is finished and exited, avoid turning the gripper quickly. It is best to unscrew it by hand to ensure that the quality of the tapped thread is not affected.

8) When the machine is attacked, the tap and the screw hole should be coaxial.

9) When the machine is attacked, the calibration part of the tap cannot be all in the head, otherwise it will cause disorder when the anti-vehicle exits the tap.

10) The cutting speed during machine attack is 6-15 m/min for general steel; 5-10 m/min for quenched and tempered steel or harder steel; 2-7 m/min for stainless steel; 8-for cast iron 10 m / min. In the same material, the diameter of the tap is smaller and the diameter of the tap is larger.

Rigid tapping

Also known as "synchronous feed tapping." The rigid tapping cycle synchronizes spindle rotation with feed to match specific thread pitch needs. Since the feed into the holes is synchronized, it is theoretically impossible to use an integral tap clamp with any tension compression.

However, the problem with this aspect in actual production is that the machine tool cannot be precisely matched to the specific tap pitch being used. There is always a slight difference between the thread processed by the machine and the actual pitch of the tap. If an integral tap clamp is used, this difference has a decisive influence on the tap life and the thread quality, since additional axial forces are applied to the tap.

If a tap clamp with tension compression is used, the tap life and thread quality will be greatly improved, as these additional axial forces on the tap are eliminated. A problem with conventional tension compression tap holders is that they cause large variations in tapping depth. As the tap becomes dull, the pressure required to activate the tap into the bore increases, and the compression stroke used in the tap drive is greater before the tap begins to cut. The result is a shallower tapping depth.

One of the main advantages of rigid tapping is the ability to precisely control depth in blind hole machining. In order to machine the workpiece accurately and consistently, it is necessary to use a tap clamp with sufficient compensation to achieve a higher tap life without causing any change in depth control.

Professional lubricants are also needed in tapping processing, which can effectively reduce the friction between the workpiece and the wire tapping, reduce wear, have a strong oil film, prevent surface scratches and wrinkles, and effectively improve work quality and work efficiency. At the same time, it suppresses the temperature rise, reduces the occurrence of sintering and card biting, prolongs the service life of the mold, protects the tool, inhibits the generation of black sludge, and does not corrode the workpiece; the cooling effect is outstanding.

It is important to select a suitable lubricant for tapping. In the case where cleaning is not required, a self-cleaning tapping lubricant is used. For difficult workpieces, pure oil-based tapping oil is required.