Using a movable steady rest on the MN-80 lathe
It shows how to cut an internal thread at the end of a long pipe using an increase in the caliper travel, steady rest, left cutters and reverse rotation of the spindle.
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Lathe MN-80. Modernization":
• Токарный станок МН-80. Модернизация
“Machine tools. Repair and improvements. Modernization":
• Станки. Ремонт и доработки. Модернизация
"Unusual work on machine tools": • Необычные работы на станках
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Address of this video:
• Токарный станок МН-80. Нарезание РЕЗЬ...
The problem was that the pipe for this MH-80 machine is very long - 330 mm. In the standard version of the machine, it was impossible to cut such a thread, because there was not enough caliper travel.
The caliper travel was increased by 30 mm due to the fact that I temporarily dismantled the lead screw reinforcement.
I took the smallest cartridge - 80 mm, because it has the smallest thickness, and it is advisable for me to fix my long pipe as far to the left as possible so that the long pipe fits on the machine.
Due to the fact that the thread must be cut with a cutter inside, at the end of not a bar, but a pipe, it is impossible to press the pipe with the center when cutting a thread, therefore it is necessary to use a steady rest when processing.
To increase the travel of the caliper, I dismantled the lead screw reinforcement. I rotate the steering wheel of the longitudinal feed of the caliper. The caliper moves to the right. The drive gear disengages from the rack. That's it, the steering wheel rotates freely.
I need to move the caliper further to the right so that I can work at the end of the pipe and inside the pipe. I put the uterine nut into engagement and rotate the lead screw by hand by the gear wheel. I rotate until the caliper protrudes from the bed by about 10 mm. For me this displacement of the caliper for threading is enough. The total displacement of the caliper after removing the lead screw reinforcement is approximately 30 mm.
I have a movable rest. A feature of the movable steady rest is the presence of two cams to stop the part. One is located on the top of the structure, the other on the side. The role of the third stop is performed by the cutter.
Therefore, the left incisors must be used. Then the cutting force will push the part away from us onto the steady cams. And the rotation of the spindle with the left cutters should be reversed.
He bore a hole for threading M30 × 1.5. Carved a groove for thread exit. Rather, for the entrance, since the thread is right-hand and the spindle rotation is reversed. And when threading, the cutter will come out of the pipe to the outside. I cut the internal thread M30 × 1.5 not with taps, but with a cutter
If the steady rest were stationary, then it would be possible to work with the right cutters with normal spindle rotation. And my steady rest is movable, so I had to make the left cutters and apply the reverse rotation of the spindle.
This is how I managed to cut an internal thread on a long pipe, applying an increase in the caliper travel, a steady rest, left cutters and reverse rotation of the spindle.
Maybe this technique will come in handy for someone.