View Full Version : 14" rockwell diagnosis (back gear)
08-29-2007, 10:55 PM
i am stumped. what would cause a 14" rockwell lathe to have absolutely no torque with the back gear engaged. i can stop a 10" 4 jaw chuck with one finger while it is powered. the motor still turns. the two power transmission sheaves still turn. i can't remember if the lead screw stops turning when i stop the chuck but i am nearly positive.
i don't have the most experience with this particular tool but by no means a novice either.
just want to slow it down to cut some threads.
I know nothing about your lathe, but it sure sounds like a clutch slipping.
08-29-2007, 11:14 PM
IIRC that lathe uses two variable speed belts for a drive.If that is the case then most likely one or both of the belts are wornout and need replacing.
Another possibility is that the movable halves of the VS sheaves are stuck either from rust or dried grease.
There are other possibilities,oil on the belts,slack adjustment etc,but most common are the belts being worn.Those belts get narrower as they wear until they fall down to far in the pulleys to drive effectively.
08-29-2007, 11:22 PM
Something may be slipping in the drive, so trace it through. So far as I know (and I'm pretty sure), there is no drive train clutch between the Reeves drive and the spindle on the 14s.
If the back half of the spindle is still spinning when you stall the chuck, it may be that the back gear eccentric shaft is not rotating the back gear assembly into engagement. When back gear is engaged, the dog clutch is opened to disconnect the front and back halves of the spindle. That allows them to move at different rates, and thus gear down the rpms via the back gear. What you describe is similar to what happens when you turn the lathe on with it in "neutral", which is the same as back gear, only without swinging the back gear into engagement with the drive and bull gears. Make sense?
08-30-2007, 12:32 AM
BadDog pretty much nailed it.
To engage the backgear, turn the knob on the upper left of the headstock to the left 180 degrees. You might have to jiggle the chuck to get the spindle to release. Then, rotate the lever next to the oil sight glass CCW so it points up and pull out on the lever. This brings the backgears into contact with the spindle gears. Do this gently and jiggle the spindle to allow the back gears to engage. Then rotate the lever CW so it points down. This keeps the back gear from disengaging at an inoportune moment.
If this doesn't work or you are confused, take the heastock cover off and all will be revealed. It is a pretty simple mechanism. Just be careful about powering the spindle with the cover off, or you will get an oil bath.
Does your machine have the lever or handwheel for speed adjustment? The lever is a later model ( slightly different than the older ones) and the manual is available at the Yahoo Rockwell board. Let me know how you do and if you have more questions.