Taper attachment binding at farthest ends
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  1. #1
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    Default Taper attachment binding at farthest ends

    I have a Sheldon with a telescopic taper attachment. Everything seems in good condition other than there is binding at the last 20% of both ends. This causes the carriage to "crab". There are two potential sources of this binding. One is the small rabbit that slides over the bar that's on the taper at attachment and the other is the large gib/dovetail that is fitted into the main casting which is bolted to the carriage. The rabbit gib I have adjusted and found it to not be the culprit. This leaves the dovetail and tapered gib under the main casting. Is there a way for me to check and or a repair the wear in these two (or more) areas?
    Thanks

  2. #2
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    Your taper attachment slides have wear in them. Worn in the middle and still new at the ends. My Sheldon had the same issue until I rescraped the slides to remove the tightness so the slide would move freely again.

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    Quote Originally Posted by 4GSR View Post
    Your taper attachment slides have wear in them. Worn in the middle and still new at the ends. My Sheldon had the same issue until I rescraped the slides to remove the tightness so the slide would move freely again.
    I thought this would be the general opinion.
    Can you tell me how big of a challenge it would be for someone that has never done any scraping to do this?
    BTW my carriage also needs some relief in the center 1/3 of the vee and flat ways. Did yours have this problem? These two places on the carriage originally had contact with the ways on the ends and, after time they wear and the entire length of the bearing surface rides on the ways. I'm sure you know that but I'm told that is another reason the carriages will "crab"???
    Thanks

  5. #4
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    To do the scraping, it takes tools made for doing so. You also have to have a decent straight edge and a good surface plate among other things.

    But after describing the problems with your carriage and bed ways, your lathe is very well worn out. At least the ways are very worn. Now you are talking about having to re-machine the ways flat and straight again, and all of this scraped and re-fitted. Not something for the average person to take on unless you have the equipment to do so. Even I don't have the equipment to do major repair like re-machining slides. I have a few sources that have the equipment to do most of the machining when I have a need for it. Then I do the rest of the process myself.

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    Perhaps but I don't think the lathe is worn out. In the past I have been able to turn tapers without an issue. Just recently I started having a problem. I am going to start another thread about an issue that arrose today as I was trying to turn a morse taper test piece.
    In previous taper turning sessions I was able to overcome the wear in the lathe by making sure I traversed the carriage well past the point that any slop would effect a cut. Today I had other problems. You can see the description in the other thread I'll be starting.
    Thanks

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    This is an old update about this taper attachment. I though I had things working well and I actually did IF I used the attachment to cut large to small travelling from headstock to tailstock.

    Yesterday I started turning another taper and ran into problems. I was turning 12L14 round bar and had a piece in an 8" four jaw. I had the piece buried to the face of the chuck and 4 inches protruding. It was indicated to less than two tenths. I had the TA situated properly and was feeding the tool toward the headstock. I began by using the hand wheel to move the apron and I could feel a lot of resistance once the cutter got into the work. I was only taking. 025" cut on the diameter.

    I looked at all the possible trouble spots and I finally determined that the problem is that the TA vee ways bind when the TA is being pulled on. I removed the shoe from the TA bar and, with only the bar still on the TA, I could pull the TA toward the machine and it would cause the apron/carriage to bind very badly. I was reaching over the lathe and pulling by hand while cranking the hand wheel. As soon as I started pulling the TA it would practically lock up. I then took the bar out of the TA and cleaned the male vee ways on the bottom of the bar and the female vee ways and gib in the casting. After assembling it was better but it got late and I had to quit before I had a chance to try it under power.

    If anyone has advice about what may cause binding in this one direction I'd appreciate it. Maybe I need to just use it travelling from headstock to tailstock?
    Thanks

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    It has been a while since I saw a Sheldon taper and I cant remember if the gib is held captive at both ends or has a single adjusting screw that fits in the gib slot.

    If it is the single screw and the gib is not held captive it * could* be camming in one direction.

    Just guessing.

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  11. #8
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    It is held with a screw head in the slot of the gib. I'm not big on this types of holding method but this particular one is a good fit and doesn't slide back and forth like many do. The slot and screw head are a very close fit.

    I've modified the compound and cross slide gib so they have a collar on a long Allen head set screw. The collar keeps the gib from moving in and a jam nut added at the end of the set screw holds it from moving out.
    The ks


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