Odd carriage feed hiccup

[kb58]

I'm very happy with my TSL-800 and have used it a fair bit. The only repair has been replacing the very worn cross slide feed screw and threaded bronze block, and that really improved things. That, however, isn't the problem.

While using the longitudinal feed, twice now, the carriage has "hesitated" briefly, in I think the same spot. I can't quite get my head around how that can be happening, as the threaded feed rod is in very good condition. If the problem is the half-nut assembly, I'd expect the problem to be occurring randomly along the rod's entire length, not in the same spot. So far this hasn't caused me major grief, though it certainly could if it happened while threading something important. I haven't disassembled the carriage gearbox yet because it's a little intimidating, so I can't say what the condition of the half-nut assembly is, but it seems like that's about all it can be. Comments?

 

[benmychree]

When it has happened, have you observed that the lead screw is turning normally? A good indication of half nut wear would be to close the half nuts while the machine is turned off and manipulate the carriage handwheel back and forth to see how much wear there is. I can't imagine why it would happen in one spot if the screw is not excessively worn. If the screw momentarily stops while the half nuts are engaged and the lathe is running, I;d look for a sheared key or pin, also look for proper mesh of the feed gears.

 

[MrWhoopee]

Is this during threading or turning?

 

[kb58]

Turning. Like I said, it's probably the half nut slipping; it's just odd that it only slips one thread in that one carriage position, and I just have to put on my big-boy pants and pull off the 80+ pound carriage gearbox assembly and dig into it...

 

[MrWhoopee]

Turning. Like I said, it's probably the half nut slipping; it's just odd that it only slips one thread in that one carriage position, and I just have to put on my big-boy pants and pull off the 80+ pound carriage gearbox assembly and dig into it...

Most lathes of any quality don't use the half-nut for turning, only for threading. Carriage feed is either driven by a keyway in the leadscrew or a separate feed shaft entirely. There is usually a clutch of some sort in the carriage feed drive. From this picture, I'm guessing a separate feed shaft.

 

[kb58]

I hardly recognized the lathe, it's so clean. I think you're right. It's only done it twice in more than a year and I'm probably mixed up. Easy enough to run it in both for a while and see what's what.

 

[kb58]

As the weather starts to cool, I'm getting an itch to get back in the garage, and this should probably be done first. I've had the carriage off previously (all ~80lbs of it!) as part of the cross slide shaft replacement, but didn't dig into the gearbox. Has anyone disassembled the carriage gearbox, meaning taken it apart, not just removing it from the lathe?

For those of you that have, are there any gotchas that I need to be aware of? Regarding the slipping carriage, if it's a clutch, how do you fix the worn friction surface, since parts are nonexistent? Also, I want to fix the nonfunctional hand oil pump and hope that it's just a dried up O-ring, and not some oddball proprietary piston seal. Anything else to watch out for?

[edit] Removed the gearbox assembly and am wondering what has to come off from the front so that the front cover can be removed. How is the hand oil pump fastened? There is nothing around the knob, just a smooth featureless flange. Is it mounted on the back face and sealed to the front cover with an O-ring?

 

[kb58]

I've given up on this for the time being, both because it needs to happen a few more times to narrow down what's going on, and because no one's suggested what to look for (as all the gears in the carriage appeared to be in excellent shape).

 

[Winegrower]

I know this is an old thread, but I had this problem on my TSL800D. There is a clutch of some kind on the power feed which was slipping, very intermittently and on heavier cuts. Take the cover off the power feed actuation lever and note two nuts on the shaft the lever engages. Back off the outer nut, and tighten the inner a bit, then jam lock it with the outer nut. This dials up the clutch pressure and stops the slipping. It might take a cut or two to get it where you like it, I suppose.

 

[kb58]

Been away, building a 3D printer from scratch... Winegrower, thanks for the input, I'll look into this. I hope it's that simple, and makes sense based upon what's been happening.