12x36 Help! What'd I break/damage/overlook?

[Smudgemo]

I hate to end the weekend on a sour note, but the carriage on my 12x36 won't run further than 8-10" from the headstock, and nothing obvious seems to be wrong. I was using the fine feed to trim down an old bolt to make a lead screw for a boring head, and while running it away from the headstock I failed to notice it had gotten to the point where the tool would hit the dead center before completing the cut. That ended up pushing the tail stock out of position a quarter of an inch or so before I noticed and shut things down. The half-nuts would not disengage (as would be expected) until I slid the tail stock out of the way, and everything seemed fine until I later tried to move the carriage out of the way for some other operation and noted that it would not go past what I think is that point. Nothing else problematic happened and it was working just fine, so it must be that one event that caused a problem.

With all levers and nuts disengaged, the carriage moves freely as it ever has, but stops at that spot less than a foot from the headstock. Everything else seems to work normally, and I'm not inclined to force anything.

Before I dive into this problem and start taking things apart, could someone offer me some help so I don't make anything worse? I don't pay attention to model numbers, so the photo is to reference which type of machine I've got.

Thanks,
Ryan

 

[Dave Smith]

Ryan--I'm a logan and sb user but I have a question---when it gets to the end of its travel does it have a clunking sound like it is hitting on something or does it just tighten up and stop?---Dave

 

[Smudgemo]

Ryan--I'm a logan and sb user but I have a question---when it gets to the end of its travel does it have a clunking sound like it is hitting on something or does it just tighten up and stop?---Dave

Almost seems like both. I forgot to mention that the lead screw seems to be preventing it from moving because it moves slightly to the right and has a bit of a clunk at that spot. But it also feels like something else is binding at the same time, as if the gibs are suddenly too tight. The manual mentions the lead screw bearing being a sacrificial part, but nothing appears to be wrong with it from casual observation.

Thanks,
Ryan

 

[CluelessNewB]

Check the bearing / bracket that supports the far end of the lead screw.

<<-- never mind that it looks like you already checked that. (My post got interrupted by dogs wanting to go out so I didn't see your last post).

 

[Smudgemo]

I checked on the way out this morning. Something is definitely is binding at the lead screw. It won't turn by hand at that spot.


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[pdentrem]

Pull the miter gear off the lead screw and check the drive key and the key way slot in that area. That is my guess.
Pierre

 

[stevecmo]

Hi Ryan,

Bummer!

I'm a Logan guy too, so not familiar with your machine but they all work about the same. Your lathe has a QC gearbox so I assume it has power feed in the x and y, but you mentioned that you couldn't disengage the half nuts. Were you using the half nuts to power the carriage away from the headstock? If so, were you using the reverse lever or did you run the lathe (motor) in reverse?

If you were using the half nuts you may have damaged them. They may have shucked a chunk and it's stuck in the lead screw. Can you move the carriage freely with the hand wheel - using the rack and pinion? You said when you tried to move the carriage out of the way for another operation but it snagged at the crash point. Again, were you moving it with the half nuts or power feed or hand wheel?

You may have to take the carriage off to find the problem.

Steve

 

[Smudgemo]

What I meant to say is that the screw turns freely by hand w/ nothing engaged until the carriage hits that spot. Then the screw won't turn at all. I can't move the carriage left far enough to see anything, so I guess I'll need to pull the lead screw to see what's going on.


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[iron man]

Are you sure you did not damage the rack in that one area??? look for damaged teeth nice looking lathe BTW. Ray

 

[Smudgemo]

Well, I think I got things working. I had the opportunity to pull the lead screw, which is a piece 'o cake on this lathe. It looks to be in excellent shape, and doesn't seem bent, broken or jammed with anything. The carriage moved quite well when it was out - even all the way to the left. I had assumed there was some wear of the ways that made it more difficult to get the carriage all the way left. Maybe not. I replaced the lead screw and found it binding in the same spot, but was able to move past it. The carriage moved freely before "the spot" and after. So I looked at the ways and noticed a nick in the corner I had never noticed before. It seemed like something to address, so I carefully stoned it to knock the damage down. I'm not sure this was an issue, but it didn't hurt to be taken care of. It was also under the cross feed screw (more or less) where things bound up.

Having put it all back together, I find that it all works perfectly except that the carriage travel past that same spot is a little tight. The travel closest to the headstock is more easily traversed, but I should go back and readjust the gib screws to make sure they are properly set (forgot to do that earlier.) The rack looks fine, but I didn't disassemble the apron to check the components.

I'd like to make sure things are 100%, so I'm open to any suggestions regarding what to do next.

Thanks for the help and compliments on the machine.

-Ryan