For precision screw cutting by tap processing, highly accurate lower holes are indispensable. It is necessary to open the lower hole that suits the tap of the tap (thickness). If the lower hole diameter of the tap is too small, the tap will break while the tap is processed. Conversely, if the lower hole diameter of the tap is too large, it will not stop firmly when the screw is inserted. Reviewing the previous process of the tap and eliminating the defect of the lower hole is the key to preventing tapping and improving the screw accuracy. In this article, we will explain the lower holes of the tap that realizes precise screws and the points of the lower hole processing by drill.
The following tasks generated by the lower hole processing of the tap include the following. The diameter of the lower hole is not appropriate, and the screw accuracy deteriorates If you open the lower hole with a drill, the effective length of the screw will be shorter The lower hole is bent and the tap is broken
.Lower hole processing by drill is an important process that affects the screw accuracy. If the lower hole diameter is small, the tool may cause a damage to the tool, and if the lower hole diameter is large, it will cause a defective processing, so it is necessary to make an appropriate lower hole according to the tap diameter and screw accuracy. The lower hole diameter is generally used with a "screw pitch" from the "screw -to -diameter". For example, for tap processing of M6 × L, [6-1 = 5] is [6-1 = 5], and φ5mm is a standard lower hole diameter. If the position of the lower hole is out of place, the tap may not be well tapped on the pitch of the tap, or the center of the tap may be shifted. At this time, the screw accuracy will deteriorate.
.If you process the hole (a hole that is not penetrated) with a general drill, you may not be able to tap to the bottom of the hole and the effective length of the screw may be shorter. Especially for thin meat work, etc., it is necessary to take measures as much as possible for the screws, so measures are required.
If the processing accuracy of the lower hole is poor, bending or deformation may increase the load on the tap and lead to the damage to the tool. In particular, the defect that the lower hole of the tap is too small, the position of the lower hole is shifted, the cutting torque is too large, and the tap is in contact with the bottom of the lower hole leads to a damage to tools. In addition, since the thickness of the powder discharged from the tap groove is not stable, it is necessary to pay attention to the entanglement of the cut powder and the damage to the tools due to the bite.
There are the following measures to improve defective tapping and prevent tapping damage.
In order to improve the diameter of the lower hole, the point is the processing process that takes into account the swing of the drill. Selecting tools and peripherals, such as carbide drills and tool holders, is also important.
If the circularity of the lower hole is low, the height of the screw will vary and the screw accuracy will worsen. High -precision carbide drills and re -man processing after drilling are effective for improving the circular degree.
.When making a deep lower hole, opening a center hole or guide hole (deep hole) before processing to improve the bite of the drill, preventing defective accuracy due to the swing of the tools and shifts.
Selecting a tool holder is important to minimize the swing of the drill during the lower hole processing. When the demanding accuracy of the lower hole is high, it is also necessary to examine the "grilled chuck" or "hydraulic chuck" with excellent mounting accuracy and rigidity.
There are three elements in the drilling of the drill: "rotation speed", "sending speed", and "sending amount". By adjusting the cutting conditions at each point, poor accuracy can be improved.
When drilling in the guide hole, the speed is reduced. By minimizing the swing due to rotation, the drill is ensured in the guide hole.
Note) Be sure to insert the drill in a rotated state. If inserted in a stopped state, in the unlikely event of an error, such as a program mistake or a setup mistakes, the machine may be damaged due to a tool and work collision*2) Processing while raising the rotation speed to the recommended cutting conditions After inserting into the guide hole, increase the number of revolutions to the recommended cutting conditions. In the case of a deep lower hole, a drill with an oil hole is discharged from the tip of the tool to discharge the cut powder. 3) Return to low speed when pulling out and pull out quickly After processing, return the rotation speed again and pull it out quickly. The load is large when the drill is removed, so be careful of the tool damage. In addition to these, performing center hole processing before drilling can improve the bite accuracy of the drill and prevent bends when entering the work.
The reason why the length of the screw cannot be secured is that the tap process cannot be processed to the tip corner of the hole drilled by the drill. It can be improved by reviewing the type and process of drills.
By using a flat drill with a flat tip, the bottom of the hole is finished flat.
When using a typical drill, the drill is processed with the drill and then sitting with the end mill. Although the processing process is increased compared to a flat drill, it is important to use it according to the type of machine tool equipped with machine tools.
In order to improve the bend of the lower hole, it is important to suppress the swing when the drill works. By processing the center hole in the previous process, the bite of the drill can be improved and the occurrence of swing can be suppressed.
In the lower hole processing, the selection of the drill type is also a point. By using a 3 -blade carbide drill with excellent cutting balance, and a coating drill with heat -resistant and lubricating properties, a high -circular hole is possible. In addition, it is necessary to pay attention to processing and curing when processing hard -cutting materials, such as processing the holes of stainless steel (SUS) with a carbide drill. If processed curing occurs, the lower hole surface will be harder than usual, and the after -step (Rima Tap) trouble and the wear of tools will be faster. Therefore, it is important to perform processing while checking the wear of the edge.
In this article, we explained the lower holes of the tap that realizes precise screws and the points of the lower hole processing by drill. Lower hole processing is important not only for taps but also for rima processing and middle tag. In order to avoid wasting the material, it is a shortcut to the effect rate whether the optimal lower hole according to the processing condition is opened.
