From: baron@linuxmaniac.net   
      
   etpm@whidbey.com prodded the keyboard with:   
      
   >    Recently I added an air cylinder to a manual lathe that opens the   
   > half nut when threading by moving the proper lever.   
   >    For those who don't know a manual lathe that can cut threads has   
   >    a   
   > leadscrew that drives the carriage along the ways when a split   
   > nut-the half nut-is clamped around the leadscrew.   
   >    When the carriage has traveled the desired distance the half nut   
   > must be disengaged. The faster the carriage is moving the less time   
   > you have to disengage the half nut. Failure to disengage the half   
   > nut in time typically results in scrap parts or worse.   
   >    As I have gotten older my reflexes  have gotten worse so I can't   
   > thread as fast as I use to. So to move the lever I added an air   
   > cylinder that is actuated by a solenoid valve that is switched by an   
   > inductive proximity switch. It works very well.   
   >    But there is some drift after the half nut opens. I can set the   
   > carriage lock so that it drags some while threading and the lathe   
   > will stop repeatably within .004". But the faster the carriage moves   
   > the more overtravel I get. Plus I don't like having so much drag on   
   > the carriage.   
   >    So now I want to add another air cylinder that locks the carriage   
   > for half a second or so whenever the half nut is opened. A 555   
   > monostable timer seems to me to be the best option.   
   >    I have some questions though. Because of the way the proximity   
   > switch works the trigger pulse to the 555 will longer than the time   
   > I want the carriage lock to be actuated. This longer pulse won't be   
   > a problem will it? My plan is to use the proximity switch to pull   
   > the 555 reset low whenever the switch is off. Then the switch will   
   > detect the carriage, the reset will go high and the trigger pulse   
   > will happen. Will this work? Do I need to just pulse the reset? I   
   > could do this with another 555, or just use a 556 chip.   
   >    The whole reason for actuating the carriage lock for just a half   
   > second or so is that the thread being cut requires several passes   
   > and I want the carriage to stop and then be released so I can then   
   > wind the carriage back and prepare for the next pass. I don't want   
   > to fuss around with pressing reset buttons or anything. The way it   
   > is now threading is seamless and reflexive, the lathe is operated   
   > just like normal except I don't have to pull up on the lever to   
   > disengage the half nut. I want to keep it that way.   
   > Thanks,   
   > Eric   
      
   Why not simply thread away from the chuck with the lathe in reverse.   
   Of course you will have to put the threading tool behind the work.   
   Otherwise it is no different and there will be no risk of running into   
   the chuck.   
      
   I thread this way all the time. Fascinating to watch threads appearing   
   at 300 rpm !   
      
   --   
   Best Regards:   
                         Baron.   
      
   --- SoupGate-Win32 v1.05   
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