Why Does The Stock Work Loose On Sherline Lathe Chuck?

Discussion in 'Horological Tools' started by Dave D, Apr 23, 2020.

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  1. Dave D

    Dave D Registered User
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    Apr 5, 2006
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    Is this a common problem with Sherline chucks? This is the second 3 jaw chuck that is giving me problems like this. Has this happened to others? Am I damaging the chuck by overtightening or something? So frustrated!
    Dave D
     
  2. gmorse

    gmorse Registered User
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    Jan 7, 2011
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    Hi Dave,

    What type of stock is it, how are you mounting it, and what operation are you trying to do on it?

    Regards,

    Graham
     
  3. Jim DuBois

    Jim DuBois Registered User
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    Jun 14, 2008
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    Well, some possibilities;
    • too heavy of a cut
    • dull cutting tools
    • wrong angles on the cutting tools
    • tenacious metal, ie tool steel in a semi-hard state or unannealed vs free machining steel
    • intermittent cuts on something other than round stock (vibration)
     
  4. Kevin W.

    Kevin W. Registered User
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    Jim answered you very well.Never run a 3 or 4 jaw chuck with nothing in the chuck, it can also damage it.
     
  5. Dave D

    Dave D Registered User
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    Apr 5, 2006
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    I have been turning round stock like brass and mild steel. I generally take light cuts, too. This is the second Sherline chuck that has given me this problem.
     
  6. glenhead

    glenhead Registered User
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    Nov 15, 2009
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    A three-jaw scroll chuck can sometimes get the stock ju-u-u-ust not quite centered in the jaws. If the stock is a bit catty-wampus it will pop into the correct position as soon as it is exposed to cutting pressure and loosen in the chuck.

    Mount the stock in the chuck, snug the chuck down, and tap on the stock a few times while hand-rotating the chuck. Then tighten the jaws again. It can also help if you wiggle-wiggle-wiggle the stock in the chuck as you're snugging the jaws.

    Give that a try, see if it helps.

    Glen
     
    Daniel Keen likes this.
  7. etmb61

    etmb61 Registered User
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    I've had that problem too with my Sherline 3 jaw chuck. Mostly with softer materials. My solution was to get a 4 jaw independent chuck.

    I still use the three jaw a lot, but it doesn't really hold well as I would like it to. One thing I've learned about it is you have to keep it clean. I bit of debris in the scroll can prevent it from holding properly. Also soft materials can stick to the jaws if they get pulled loose so you need to look at those too.

    Eric
     
  8. MARK A. BUTTERWORTH

    MARK A. BUTTERWORTH Registered User
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    Jul 4, 2009
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    If the stock is small enough to put into a collet you will get much better results, especially with the ER-16 collets in the Sherline

    B2F4E277-FE98-4877-B151-4B4875DFB3E9.jpeg
     
  9. Jim DuBois

    Jim DuBois Registered User
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    I suspect another issue with the Sherline 3 jaw has to do with tightening it up with the pair of Tommy bars. I think I don't get as much clamping force using them as I apply to a conventional chuck using a geared key. I have a couple of the Sherline 3 jaws I use, more on my mill than anything else.
     
  10. wefalck

    wefalck Registered User

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    I have been using Sherline-chucks now for some 20 years on my LS&Co. WW lathe without any trouble, mainly for coarser work. As with any stock material that is not perfectly round, you need to tighten the chuck by hand and then try whether the material comes loose, when you try to turn it by hand. Then re-tighten in the new position. If the material then is not gripped securely with the aid of the tommy-bars, you should not use it in a three-jaw-chuck.

    NB. ER collets only hold securely, when the material goes all the way through them, due to being double-slotted. You can damage the collets when clamping shorter material, as this forces the collet deeper into the conus by bending it over the edge of the clamped material. ER collets were actually designed for tool-holding.
     
  11. Jerry Kieffer

    Jerry Kieffer Registered User
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    Dave
    At the School in Columbia where Sherline equipment is used, this will occasionally come up in class.

    For small Lathes, there are two types of chucks that are commonly available. First there is the common tommy bar versions that have the issue you mention for a small number of people, and the keyed versions that are generally larger, thicker and less versatile. Sherline only provides the Tommy bar version, but Bison provides a keyed version of equal quality at a higher price.

    While others have compiled a list causes with all chucks, the early Sherline chucks did have an issue. They only had a few tommy bar holes and tightening was limited to two hands at awkward positioning making proper tightening difficult for some. In class where the issue can be diagnosed, most of the time, the chuck is not tightened properly for whatever reason. The other most common cause already mentioned, is stock extended to far in front of the jaws without support.
    While most people do not have an issue tightening or opening a Sherline chuck, for those that do including myself from time to time, my advise is as follows.

    The way to tell if a sherline chuck is properly tightened is when the question is, how do I get it open.
    At any rate, for many people, tightening any tommy bar chuck with two hands can be less than sufficient under heavier loads. The current Sherline Chucks have many more holes than early versions allowing for positioning of the tommy bars per the first photo when tightening. This allows one to squeeze the two bars together with one hand typically providing a much tighter condition than with two hands. Next question, how do I get it open when tight. In this case, if the bars can again be positioned per the second photo, an object like a hammer handle can be inserted as illustrated and rotated easily opening the chuck. If none of this seems execeptable, the larger Sherline OD chucks give greater leverage requiring less effort to properly tighten and loosen.

    Jerry Kieffer

    fullsizeoutput_578.jpeg fullsizeoutput_579.jpeg
     
  12. measuretwice

    measuretwice Registered User

    Jul 28, 2019
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    What Graham said, we need complete info on what and how you're cutting it. Works loose how? starts pull out, push in, flops around, falls out? There are always lots of different things going and we have minimal info.

    you can damage a chuck by over tightening. You could deform the scroll, but you're really going to have to apply alot of force to do so, i.e. putting a bar on the chuck key sort of thing. A good chuck should be able to stand all the force a man can put to it through its intended tightening mechanism.
     

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