It is well known that high hardness tapping has always been a challenging problem in all taps using taps.

The reason is very simple, fee knife! A tap with hundreds of thousands of costs will probably fail to be processed by only a few or dozens of threaded holes. This undoubtedly greatly increases the cost of taps.

So, is there a better way to solve or improve the condition of the tapping knife for high hardness materials?

The answer, of course, is affirmative. Under the existing conditions, how to optimize the high hardness alloy material by the common taps is optimized.

1. using domestic common M8 to tap processing standard, in the tapping process often appears not to attack the screw, or tap off phenomenon. Subsequently, the replacement of imported high hardness tap tap, the results still broken, affecting the normal production workshop.

2. Explore the reasons for breaking the tap 

There are many factors that cause the taps to break, but the main factor is that the cutting resistance is too large. The cutting resistance of the cutting is mainly influenced by the cutting load of the taps. The cutting load is mainly influenced by the cutting thickness of the cutter teeth of the taps, the material material and the heat treatment. The relationship between the structural parameters of the taps and the cutting thickness has the following relation:

Ac=P. TanKr/Z

In the formula, Ac is the cutting thickness for each tooth of the taps; P is the pitch of the taps; Kr is the guiding cone angle; Z is the number of taps.

Analysis of the type that can be cut by changing the structure parameters of the tap itself to change the tap force, thereby changing the cutting resistance. For domestic common taps, the slots of the taps are fixed on the premise of the screw pitch of the taps. Furthermore, we can reduce the steering cone angle of the taps to reduce the cutting torque.

In the actual production process, use the standard to tap ordinary carbon alloy steel material, tap the hardness is 59 ~ 62HRC, larger than the hardness of the workpiece was a real attack thread, is due to the long tap point and hinge bar afterburner distance is too long, the moment, when tapping tap the unbalanced stress cone, wire twisting (not smooth rotation around the axis), which cannot be tapped. Therefore, the cutting force distance of the taps can be improved by reducing the length of the taper shank.

3. common taps

Through comparative analysis and comprehensive data, we can see that a more reasonable cutting thickness should be controlled at 0.03 ~ 0.06mm, and the reasonable taper steering cone angle should be controlled at 6 to 12 degrees. It can be divided into 3 angle stages, plus fourth standard taps, for short, 4 cones, while improving the design of taps under the premise of ensuring the strength of the cutter body and preventing chip extrusion.

First of all, by grinding domestic ordinary tap, screw tap cutting guide cone angle grinding is 7 degrees, fully tap the threaded part reserved for 3 buckle silk, make point extends to the cone shank taps, shortening the force torque, enhance the cutting torque of tap, while the length of the handle from the tap 50mm grinding to 30mm, further enhance the cutting torque tap (pictured above), in order to eliminate the increase of chip, can appropriately increase the groove length.

Then, the cutting guide cone angle grinding taps second to 9 degrees (see below), fully tap thread part reserved for the 7 button wire, so that the force also extends to the taper shank. The cutting guide cone corner third taps grinding is 12 degrees (see below), fully tap thread portion reserved for 9 buckle silk, force is also appropriate to extend fourth to 4 standard tap tap, tap root force, the cutting force is uniformly dispersed in 4 on tap.

Second, grinding the rear angle of the taps. For materials with higher hardness, in order to reduce the friction between taps and workpieces, the improved taps were grinded with flake grinder or tool grinder, and the thread corners of grinding taps were grinded to 4 degrees to 6 degrees. The order of tapping is: using 12 degrees taps to attack the thread, using the 9 degree taps to attack the thread, and using the 7 degree taps to attack the thread, and to use the common taps to attack the thread.

In the tapping process, prone to tap for fracture according to different hardness materials, increasing workpiece bottom diameter properly, easy to eliminate metal cutting chip.

4. tapping method

For the machining of the thread of the workpiece, the 3 reformed taps can be added with 1 standard taps, with the hinged bar, and the taps are lubricated, and the thread is completed in turn. In the process of tapping, we should pay attention to that the taps and workpiece are kept perpendicular to the processing holes, and the clockwise rotation of the hinges should be done moderately. In order to avoid the tap breaking, it is necessary to increase the number of rotary rings of the taps and discharge the deep holes in time.

Based on the standard thread diameter (tolerance range), increasing the diameter of the inner threaded hole, the cutting resistance decreasing tap, improve the cutting conditions, to prevent the tap off prolong the life of tap.

5. conclusion

The strength of the taps is obviously enhanced when the improved taps are used to attack the thread. In 5 years, 44HRC high hardness alloy parts processing and heat treatment hardness of 38 ~, there has never been a real thread tap and tap off phenomenon (tap taper can be used to modify the use of the old tap).

In the process of daily tapping, if the workpiece is hard again, the number of taps can also be increased. The surface quality of the machined inner threaded holes is good, thus ensuring the quality of the product.

Hangzhou GSR-Threads Tools Co.,Ltd

Address：No.381,Tianjiali,Tianfeng Village,Yiqiao Town,Xiaoshan,Hangzhou,311258,China

Tel：     +86-571-826 883 63

Phone：+86 182 584 02850

Fax：    +86-571-838 647 37

E-mail：info@gsrthreads.com