Correct sequence for thin walled parts

  1. earthman Member

    Messages:
    1,163
    Question for the trained machinists, what's the correct sequence for say holding and making or modifying a thin walled part on a lathe?
    From my own experience, I know that a 3 jaw chuck is far from ideal for say holding a some what thin hollow tube, chances of that not deforming are slim,....I don't yet have a collet chuck for my lathe, if I did, what thickness of material could you get down to/get away with shall we say??

    I've just made this sleeve/adapter part from a scrap piece of solid bar, drilled/bored the hole first then cut the internal thread, turned the outer diameter down to size before parting off. The final walled dimension is just over 1.5mm so maybe not that thin/risky when it comes to steel? Could I have drilled/tapped right the way through without fear of the part deforming?? What if it were say delrin, any tips/guides on what you could go down to size wise with which material without it screwing up?

    adapter.jpg
     
  2. Wedg1e

    Wedg1e They call me Mr. Bodge-angles

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    6,194
    Location:
    Teesside, England
    I tend to do the internal work first, then shave down to size - bearing in mind you then take lighter cuts from the OD than you would/could if it was solid.
    Also, with an internal thread, that's the tricky bit, so if you spend time on the OD and then ruin the thread it's time wasted. Start by ruining the thread :D
     
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  3. Hopefuldave Intergalactic pot-mender

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    1,151
    Location:
    The Shed of Danger, surrey, England
    Poor man's collet helps, piece of thick-walled tube with a suitable bore, slit down one side if you're holding something that's already thin walled. Not perfect, but usually good enough

    Dave H. (the other one)
     
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  4. Bill Edwards Member

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    4,898
    Location:
    Scarborough, North Yorkshire
    This is worth watching:

     
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  5. Pete.

    Pete. Member

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    Kent, UK
    I rough the inside, rough the outside then finish the inside and finally finish the outside. Be sure to cool down before finish turning. When I was learning I was taught an important lesson when I turned a piece in stainless then drilled it through only to find the OD had grown.
     
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  6. earthman Member

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    1,163
    Thanks all, great tips there, never even thought of the poor man's collet. Lol

    The correct sequence of doing things kinda becomes obvious when you put some thought into it and have screwed up a part or two hey. Lol
     
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  7. Bill Edwards Member

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    4,898
    Location:
    Scarborough, North Yorkshire
    Messing up a part teaches you pretty quickly!
    Rather annoying sometimes though.
     
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