Craftsman 101 automatic feed problem

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grain914

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Hi -- I recently bought a Craftsman 101.21400 lathe. Even though the laead screw continues to turn, the cutting tool stops. The half-nuts and lead screw seem to be in good condition and clean. I have tried Robert D.'s advise to Alanv (Hobby Machinist 03-20-13) to adjust the lead screw by running the carriage to each end with the lead screw's mounting screws loose, closing the half-nuts on the screw, and tightening the mounting screws with no success. Robert D. also mentions a "detent spring and ball that operate on the M6-38 cam." For my detent ball to drop into my cam the half-nut lever must be at about 6 O'clock; but when the lead screw is in place this lever will only go to about 3 O'clock. Is the half-nut assembly assembled incorrectly. If not, how can I correct it? If so, any other advise to solve my problem?
Grain914
 
The detent should not be at 6 oclock. Check your half nut assembly.
 
After posting my original message I, again, removed the lead screw and checked the location of the detents. One was at approximately 12 O'Clock, another at 6 O'Clock, and still another at 8:30. Reasoning that someone had assembeled the half-nut lever up-side-down, I again took the half-nut assembly apart and reassembeled it with the nuts open at 6 O'Clock and closed at 8:30. This has NOT solved the problem: with the lead screw rotating, the cutting tool did not move. The half-nuts look to have very little wear. With the half-nuts removed from the assembly and useing my fingers to squeze them together over the lead screw produces a great deal of "purchase," In his advise to "Alanv," that I mentioned in my original post, "Robert D." suggested adjusting the half-nuts. I can find no adjustment. Any advise?
Grain914
 
I just took a look at the manual. Do the half nuts move when you rotate the lever? About the only things that can cause this is 1) a worn cam, 2) cam engage pins missing on the half nut, 3) worn half nuts.

If you don't already have one, here is a link to the manual. page 5.1 http://vintagemachinery.org/pubs/222/1924.pdf
 
Allan: thanks for the reference to the manual.
Yes. The half-nuts open and close when the half-nut-lever is moved.
When I posted that the two of the detents were at 6 O'Clock and 8:30 I was relying on my memory. Just for the recort they are at approximately 7:30 and 9 O'Clock.
All of the parts look good with very little wear. However with the half-nuts closed there is enough vertical "slop" the assembly so that I can slip the shank of a half-inch drill through them. Obviously this is bad since the lead screw mikes at almost exactly 0.500." The question is what to do about it. The pins look unworn as does the cam and the guide and the half-nuts seem to have very little wear.
Any ideas.
 
The only thing I can think of at this point is to ''assemble'' the whole mechanism in your hand and and see what position the cam is in when the pins are engaged and the half nuts are closed. It almost sounds like something is not made correctly, maybe those are aftermarket half nuts, or an aftermarket cam.

When in the closed position, the half nuts should be pretty much together.
 
Does the half nuts have a # on them if so make shure the are the right ones. And not for the larger ones for a 3/4" lead screw.
 
I'm puzzled why your handle wants to lock in at the six o'clock position. It's almost like something is out of sync by about 90 degrees. On my 618 I have full-open nuts with handle at about 1:30, and full-closed and locked onto the lead screw at 3:00. Here's a picture I took of mine from the back side before I pulled it apart one time. It might help to narrow down if whoever owned the machine before put things together in the proper orientation. At least you could take one thing out of the list of variables.

-frank

image.jpg image.jpg
 
Thanks kd4gij, JimDawson, and frankist for you help.
While looking for parts on eBay, I encountered a picture of a half-nut-cam, lever, and what appears to be a shim/washer. Checking the depth of the half-nut-cam lever recess in my carriage and the thickness of my half-nut-cam showed a 0.020 inch difference. All I could find in my scrap box was a 0.016 piece of brass from which I made a shim. The bottom half-nut is now rock solid and the top half-nut has significantly less "slop" tha before.
This shim is not shown in the Craftsman manual; but neither is the very short, headless screw that holds the detent ball and spring from falling out the bottom of the carriage.
I have not yet tested the lathe; but I believe the problem is solved.
Grain914
 
I ended up shimming mine too and seemed to solve the problem.

I know there is some wear in the nuts and the screw too but dimming it seemed to take the play out and tighten everything up.
 
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