Crankshaft repair

  1. Maker

    Maker nEw mEmBeR

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    Dad's just got this old "Pank" pump, should look quite nice cleaned up but internally it's in quite a bad way, one of the conrods is missing, the other is very worn and the crankshaft has a little bit of pitting. :whistle:
    [​IMG]

    [​IMG]

    I think the conrods are just short enough to fit in the swing of my lathe, if not I'll need a boring head for the mill but I'd offered to make them before I saw the state of the crank. Chances are I'll just leave it as is, he's never gonna run it long enough to wear out a new conrod but it got me wondering if it could be repaired, how would you hold a part like that though? Obviously in a four jaw chuck and indicate on the journal but what do you do at the tailstock?

    Once I've got it held I can turn it back to good metal and either make new conrods to fit that or weld a sleeve on and turn it back to it's original size.

    Surprisingly, the crank end of the remaining conrod doesn't look too bad, the piston end on the other hand...
    118762856_755253085261108_4392583645960230896_n.jpg
    I assume the wrist pin is similarly pitted and I'll be making a new pair of those too. :laughing:
     
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  2. eLuSiVeMiTe

    eLuSiVeMiTe Member

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    Good question.

    Tack a bit of flat bar on the unsupported end and center drill the 3 centers?
     
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  3. barking mat

    barking mat Barking at Pigeons

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    Cor blimey governor!
     
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  4. Maker

    Maker nEw mEmBeR

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    I considered that but aligning it is the issue, unless you can somehow set it up unsupported at the tailstock, maybe with a fixed steady on the journal to be machined and then drill the center bang on where it needs to be, you'd never get your drilled bar lined up. I suppose it's not that critical, you could be about a 1/4" off where it should be and it would still work just fine. :whistle: I might go with this actually.

    The other idea I had would be to mount a four jaw chuck on a bearing on a morse taper to fit the tailstock, then dial it in just like you would at the headstock end. A bit like the boring head idea you deleted. :D Biggest problem here is I don't have another four jaw. :(
     
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  5. eLuSiVeMiTe

    eLuSiVeMiTe Member

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    Lol you saw that. Would need the other 4 jaw to rotate and could be driven by the spindle via the crank.

    Center spots is probably the easier option with a fixed steady to get it dialed in.
     
  6. Morrisman

    Morrisman Forum Supporter

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    Considering it was still running like it is, would it be possible to simply smooth out the journal with a flat file, emery strip etc? Or is it too lumpy and bumpy for that?
     
  7. Agroshield Member

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  8. Agroshield Member

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    One of these (revolving tailstock chuck adapter with Myford thread - also available with Boxford thread):

    https://www.ebay.co.uk/i/370603921920

    could be a good start. Major thing to think about is when used in T/S, the chuck will try to unscrew. Could be overcome by running in reverse with upside down tool.

    Look on YT for 'crankshaft grinding' as some typical setups there. E.g.


     
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  9. the snooper

    the snooper getting older by the day

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    If your making new conrods you may aswell find someone that can take the big ends back to a decent surface and make the conrods to suit
     
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  10. Maker

    Maker nEw mEmBeR

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    It's a rusty old pump he paid about thirty quid for, someone kitted up to do it properly would charge ten times what the thing is worth. For the use it's going to see when it's repaired, leaving the shaft as it is would honestly be fine, I'm really just doing it because I can (Or rather, considering doing it because I like to think I can :whistle:).
     
  11. eLuSiVeMiTe

    eLuSiVeMiTe Member

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    I spent ages making a fixed steady to repair a motor shaft. Probably wasn't economic but I enjoyed it and have a steady to use for other projects
     
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  12. Maker

    Maker nEw mEmBeR

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    It won't be much use if the lathe ever sells. :whistle:
     
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  13. eLuSiVeMiTe

    eLuSiVeMiTe Member

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    Aye. Easy come easy go.

    Made my office a much nicer place to be though and given everyone a lot more space
    IMG_20200902_182132.jpg
    Can't find any pics of how it used to look but that whole wall was covered by a big black kalex unit and stacked filing cabinets. Made the room feel dingy and tiny

    Easy to find another lathe when the time comes
     
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  14. pressbrake1

    pressbrake1 Forum Supporter

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    For cranks I use a block bored out to crank diameter then bolt it to a face plate and clock in
    Split block on tailstock end
    Minor faffage but works well
     
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  15. Maker

    Maker nEw mEmBeR

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    I'm more into listening to music than making it (I did have six months of guitar lessons when I was 10 :whistle:) but the gear looks very cool. I can't see me swapping my workshop for anything but a bigger workshop though. :laughing: The painting above the monitor caught my eye. ;)

    I was hoping you'd have some input. Can you elaborate on the tailstock end? Are you clocking the part in then drilling your spilt block for a live center?
     
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  16. pressbrake1

    pressbrake1 Forum Supporter

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    2,881
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    Correct, sounds hoochy but works well especially if you can cobble up a toolpost grinder
     
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  17. Seadog

    Seadog Forum Supporter

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    Why would that be? It's a right hand thread.
     
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  18. Maker

    Maker nEw mEmBeR

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    I'll give that a try then. :D Hopefully it's not been hardened, I've got a nice motor stashed away for a toolpost grinder but I'll be going back to uni in a couple of weeks so I doubt I'll have time for such a project.

    It's only just occurred to me the tool will have to be some long skinny boring bar type thing to fit down between the webs, now I really hope it's not hardened. :ashamed:
     
  19. eLuSiVeMiTe

    eLuSiVeMiTe Member

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    Old style tool holder maybe.

    images.jpeg
     
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  20. Maker

    Maker nEw mEmBeR

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    I've got a couple of those actually but no 1/4" HSS to fit them. I've got some big blanks I reckon will do it, must be 5/8 or 3/4". A parting blade might do the trick too
     
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