Lathe Drilling and Tapping Thread Processing Method and Tooling Design
May 27, 2020
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During lathe machining, the parts rotate continuously, which is more efficient than other machine tools. However, in the case of small parts and a large number of parts, repeated installation and removal of parts on the chuck will take a long time and the relative efficiency will decrease. In order to shorten the auxiliary time and improve the processing efficiency, the research and design installs the tool on the chuck and continuously rotates. The parts only perform the feed movement. When the part is replaced, the tool can continue to rotate, and the replacement part is simple and convenient, and the time is short.
A company processed a batch of hex nut parts, size M20, which required drilling and tapping. The drill or tap was installed on the chuck for cutting movement, and the part was installed on the tool holder for feed movement. Effect.
Nut structure analysis and processing characteristics
The nut material is 45 steel, the blank is cold forging blank, the inner hole has a processing allowance of 2mm, and the outer hexagonal outline size is basically uniform, without processing. When processing, it is necessary to remove the 2mm excess of the inner hole first, and then tap the thread with a tap to complete. Machining the nut screw with a lathe is to clamp a single nut on a three-jaw self-centering chuck, and then use a turning tool to process the inner hole and screw, or install the drill bit and tap on the tailstock of the lathe, use the drill bit to drill Tap screw thread. Using the above two methods, a single nut blank is installed on the chuck, the nut rotates, and the turning tool or drill bit (tap) is fed into the feed movement. The operation is repeated, which is time-consuming and labor-intensive, and the processing efficiency is low. In order to improve the processing speed, the research decided to design a simple tooling, install the drill bit or tap on the three-jaw self-centering chuck, and make the rotary motion, and the nut to be processed is installed on the tooling, and the feed motion constitutes the processing mode.
Design and use of drilling methods and tooling
According to the idea of the rotation of the drill or tap and the feed movement of the nut, install the drill or tap on the three-jaw self-centering chuck, design a simple tooling, install the nut to be processed in the tooling, install the tooling on the tool holder, by The tool post moves axially to realize the feed motion. The drilling method and tooling design are shown in Figure 1.
Figure 1 Sketch of drilling method and tooling design
Lathe chuck
Drill
Support bending plate
Tool holder
Connecting plate
Coupling bolt
Set bolt
Nut to be processed
Base plate
Front end plate
Drill sleeve
Upper cover plate
The tooling for installing the nut is composed of the supporting bending plate 3, the connecting plate 5, the connecting bolt 6, the positioning bolt 7, the drill sleeve 11, the upper cover plate 12, the front end plate 10 and the bottom plate 9, etc. The support bending plate 3 is installed on the lathe tool post, and long holes are machined on both sides of the connecting plate 5, and the connecting bolt 6 is connected to the supporting bending plate. Due to the existence of long holes, the coupling plate can move up and down on the supporting bending plate to determine the processing position. The set bolt 7 is installed on the upper cover plate 12, after the processing nut is installed in the tooling, tighten the bolt to lock it. The drill sleeve 11 is installed in the front end plate and is used to guide the drill bit or tap to ensure accurate processing. The drill sleeve is made of 45 steel material and quenched to ensure wear resistance. The upper cover plate 12, the front end plate 10, the bottom plate 9, and the connecting plate 5 are integrated by welding. Its width is equal to the maximum size of the hexagon of the nut to be processed.
Before processing, install the drill bit on the three-jaw self-centering chuck and lock it. Then install the support plate 3 on the lathe tool post and lock it. Install the tooling to the support plate, level it, and tighten the coupling bolts slightly.
The first piece is processed, put the nut to be processed into the tooling from the side, as long as it does not exceed the tooling width, tighten the tightening bolt 7 to fix the nut. Find it right. Move the connecting plate 5 up and down, and move the slide plate in the tool holder perpendicular to the axis of the lathe. Determine the position of the center of the drill sleeve and the turning center of the lathe. After confirming that the two coincide, tighten the connecting bolt 6 and lock the slide plate. At the beginning of the processing, the spindle drives the drill bit to rotate, and moves the small slide of the tool holder axially forward, and the drill bit guides the drilling operation through the guide of the drill sleeve. After the drill bit penetrates the hole on the coupling plate, it is determined that the drilling is completed. Move the small slide of the tool post backward, the drill bit leaves the tooling, loosen the set bolt 7, put the second nut from the side, the first nut is squeezed out. Tighten the set bolt 7 again and lock the nut. Move the small slide of the tool post, and the second processing starts. The drill bit keeps rotating throughout the processing process, and only the tool holder moves axially. Since the correction of the first piece has been completed, the subsequent processing does not require the correction process, which greatly improves the processing efficiency.
Design of tapping tooling
When tapping internal threads, in order to prevent the transmission error between the screw and the tap of the machine tool and cause the phenomenon of thread buckling, a special tapping tool chuck is designed, as shown in Figure 2.
Figure 2 Sketch of tapping tooling design
Tap
Drill sleeve
Set bolt
Clamp
Cylindrical pin
One end of the clamp 4 is installed on the three-jaw self-centering chuck, and the other end is installed with a drill sleeve in the inner hole. A long hole is axially penetrated and processed on the clamp for use with the cylindrical pin 5. The drill sleeve is used to hold the tap. The part is made of 45 steel and quenched. The cylindrical pin 5 has an interference fit with the drill sleeve to drive the rotation of the drill sleeve, and cooperates with the long hole on the clamp to enable the drill sleeve to have 4mm of axial movement to eliminate transmission errors and prevent buckling. . The set bolt 3 mainly serves to tighten the tap.
When tapping the thread buckle, first remove the drill bit, install the tapping tool chuck on the three-jaw self-centering chuck, and lock it. The position of the tooling installed on the tool holder remains unchanged, and the nut to be tapped is fed into the tooling, and the set bolt 7 in FIG. 1 is tightened to tap the thread. The spindle drives the tap to rotate, and the tool holder moves forward. After the cutting part of the tap passes through the nut, the spindle reverses and retracts the tool, and the tool holder moves backward. The first nut is tapped. Then feed the second nut and extrude the first nut at the same time, repeat the above operation, and so on.
Conclusion
The same lathe processing method, using simple tooling, changing the installation position of the tool and parts, realizes the cutting motion of the tool and the feed motion of the parts, speeds up the cutting speed, simplifies the operating procedure, saves time and labor, and greatly improves the processing efficiency .