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| Swingup external threading tool |
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| andyf:
--- Quote ---Berndt: when I reverse the machine the chuck will start to turn and at about a 1/4 of a turn of the chuck the lead screw will finally start to turn. Then after the chuck has made almost a full revolution backwards the carriage will finally start to move. Have I made this clear enough to understand? That is one reason I think this tooling will not work in "my" machine. --- End quote --- To my way of thinking, Berndt, it won't matter if the chuck starts turning (in reverse) before the carriage starts moving. The flank of the part-cut thread will rub on the side of the tool, and move it up out of the way. I can see that if your chuck turned more than 1800 before the carriage moved, and you were cutting a small pitch thread, the tool might rise up the flank of the thread and then drop back down the other side of it, but all that would happen is that the thread flank would push the tool up again once the chuck had gone round 3600, with no detriment to the tip of the tool. A simple test could be arranged :smart:: Instead of a tool, grip a bit of thin slightly springy metal with a 600 point on the end in the toolpost at centre height, with lots of overhang so it can spring up and down. Engage its point in the thread of a bolt held in the chuck. Then, with the change gears set up for the same thread as the bolt, try running the carriage to and fro. My bet is that the tip of the "tool" will rise and fall as required. If the tip gets mangled, I'm wrong :bang:. Andy |
| Bernd:
Andy, That sounds like a good test. Will have to try that. Won't be right now though. Thanks. Bernd |
| bogstandard:
Bernd, When Stew called around the other day, and we cut that very large thread, we encountered a major problem when the tool was deep in, about 4mm (0.160"). On retracting out of the runout, the side of the cutting tool jammed on the side of the thread. It was caused by the swing part of the tool not being able to rise enough to clear. All I did was a quickie hack out of the main tool holder on the top overhang. Once that was done, and the tool could lift as far as it wanted, it just climbed as high as it needed to go, and dropped back into the cutting position when it reached the end, as shown in the short vid. So even if it was riding on the very top of the tips of the threads already cut, once it had dropped off the end, and if you left enough runup to the job to get all gears back into synch, I don't think you would have any problems at all. John |
| Ned Ludd:
Hi Mr Standard, I think that is what your "detractors" were worried about, the not being able to rise up enough. Sounds like your fix (could you call it the Viagra modification, getting more of a rise. :lol: sorry 'bout the bad joke could not resist) has done the trick. Ned Ludd |
| andyf:
--- Quote ---Bogs: So even if it was riding on the very top of the tips of the threads already cut, once it had dropped off the end, and if you left enough runup to the job to get all gears back into synch, I don't think you would have any problems at all. --- End quote --- Not sure that gear sync would be an issue, Bogs, because the drive from spindle to saddle will be engaged throughout. Won't the tool just need a moment to drop down again before starting the next cut? Unless you are working at lightning speed, that will happen while you are stopping, changing the spindle from reverse to forward, and starting off again. Incidentally, Mike Cox has viewed this thread and says "I am amazed that my simple idea could generate so much interest and discussion. I only wish I had the skill and equipment that Bogs has. It is very satisfying that in the hands of a skilled worker the idea was taken to perfection." Andy |
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