Half Nut Lever Not Working - Remove The Carriage?

[Cody Killgore]

Hey guys,

I know I've been posting a lot about my recent sheldon xl-56 purchase. The previous owner told me that the half nut lever was not working. He said he had someone come and look at it and they said it appeared to just need cleaning. It moves a little then just stops. I can see the half nut starting to close then it just gets to a point where it comes to an abrupt stop. I guess my question is, how do I go about that cleaning?

I'm thinking I might have to remove the whole carriage so I can get to the back of the apron (I think I'm using those terms right...). If that is the case, how do I go about removing it? I have no clue where to begin on that process.

Any guidance is greatly appreciated!

Here is a picture of it again.

 

[cathead]

More than likely, you will want to disassemble the apron some to find the problem. I have had
to do this several times. There is usually a cam kind of thing inside or maybe a dog that keeps
the half nuts open when running the feed. I would remove the screws on the top
of the carriage and also the bolts that hold the lead screw in position. They are on the right very
end of the lead screw. Then you can probably tip the top part of the apron out a bit and
look at the workings behind using a flashlight and a mirror. Usually you can see the problem
and remedy the situation. If the lathe has had a lot of use, it might be a good time for a
disassemble and clean procedure. It is really not all that difficult to accomplish so worth
considering. Also I have seen where jiggling the X and Y feed controls and taking off the pressure on
the clutches will free up the half nut lever if they happen to be stuck. It's all pretty straight forward
so just rip into it. I would be happy to help along if you like so feel free to send me a PM. It's good
take it apart get a better understanding of the inner workings. I see you have an Enco mill. I have
one that looks just like yours and have been very happy with it. Mine is a step pulley 9x42.

 

[wa5cab]

Cody,

I don't know anything specific about the Sheldon but just to make sure, are you trying to engage the half nuts with the lead screw turning or with it stopped? When stopped, I would guess that there is about a 1 in 8 chance that they will close without having to rock the carriage. With the lead screw turning, they should engage at least any time a line on the threading dial lines up with the witness mark.

I can't tell from your photograph whether the carriage apron is a separate part or whether it and the saddle were cast as one piece. If the latter, your only choice is probably to remove the carriage from the bed.

 

[hermetic]

Hi Cody, I am not familiar with the lathe at all, but on many lathes the apron controls are interlocked so that the half nuts cannot be engaged at the same time as the feed for surfacing and sliding are engaged. try the halfnuts again after you have changed position of all the apron controls, and try each seperate position of each control (if you see what I mean) Does the half nut lever move at all, or does it appear to be completely frozen? can you take off the screwcutting dial indicator and see the half nut mechanism. the half nuts are usually opened and closed by two pins sliding in two semi circular slots, it is possible that one of the pins is bent, or has come loose and jammed the machanism.
Phil
UK

 

[hermetic]

Try with the centre yellow lever in the middle position, that should be "neutral"

 

[Cody Killgore]

Okay guys. I went to check it out.

@cathead I really appreciate the offer to help! I may hit you up about it. It appears that I won't be taking it apart right now, but I still want to do so in the near future to clean it out really good.

@wa5cab @hermetic
Thanks guys! I started playing around with the levers. Hermetic, you were right about putting the feed change lever in the neutral position. I had no idea I needed to do that. I just assumed since the previous owner told me it did not work, that it did not work. I had not thought that he may not have known how to use it either, lol.

That fixed it though!! Thanks so much! Saved me some serious hassle. Turned my first threads yesterday and they turned out great!!

 

[hermetic]

GET IN!! glad to help!These controls have to be interlocked, just imagine what would happen if they weren't and you selected both feed and screwcutting at the same time, OUCH1
Phil
UK