motor shaft repair

  1. johnser

    johnser Member

    Messages:
    2,113
    Location:
    North Cornwall
    Have a 5hp motor with the front shaft worn where the bearing sits. Has been chattering for long enough to wear from 40mm down to ~39.6 in places.

    I've welded a less valuable one and turned it down in the lathe but remember it not being easy. Aside from that, I can't remember how I approached it! Any tips? I guess I'll have to do opposing runs cooling the shaft between goes....

    Alternatively, seeing as it looks like it'll need to be lathed either way, I could turn the 38mm pulley shaft the next size down and machine a sleeve for the bearing to sit on or get an undersize bearing if one exists. Think I'd like to keep that as a plan B though as my machining is not all that hot.
     
  2. 8ob

    8ob Forum Supporter

    Messages:
    6,678
    Location:
    moscow on thames
    There is a corrugated shim material that crushes down to size, you may get away with a strip of that around the shaft where the bearing sits and press it back on.

    Bob.
     
    slim_boy_fat and johnser like this.
  3. Agroshield Member

    Messages:
    1,364
    The trick with motor shafts is to machine them down enough first before applying weld build up. Then when you remachine to size, you are not cutting a mixture of old and new metal.

    As you say, do not let it get too hot in one place. Balanced runs are good applied with patience.

    Set it up true (do both ends have centres in them?) and find a reference surface that is not going to distort with welding (you may have to use or modify the laminations for this). After welding, set up true again and recut welded-end centre.

    There is a product called a Speedi-sleeve that can be used in this application.

    https://www.skf.com/binaries/pub12/...1337_2-EN-SKF-Speedi-Sleeve_tcm_12-128020.pdf
     
    nickk, hunter27 and johnser like this.
  4. hobby_machinist Member

    Messages:
    56
    Location:
    Croatia
    What welding proces did you used, mig wires often has a lot of manganese in them so the weld gets harder as you machine it, the workshop where i sometimes work only uses 7018 electrodes when shafts needs to welded and machined
     
    johnser likes this.
  5. johnser

    johnser Member

    Messages:
    2,113
    Location:
    North Cornwall
    Excellent help thanks!

    Sounds interesting, you know what it's called/where to look at it?

    Good tip regarding machining down first, hadn't thought of that and makes a lot of sense.

    Unfortunately only a centre in the front end, but the rear can hopefully be carried somehow.

    Think the speedi sleeves are just for seal surfaces?

    Interesting thoughts on using 7018s. I was indeed tempted to use mig, just for convenience and to suit my (lack of) ability. Might be a toss up between a half decent weld or a half decent finished surface!
     
    slim_boy_fat likes this.
  6. hobby_machinist Member

    Messages:
    56
    Location:
    Croatia
    Its not a T joint or overhead weld so you have to worry about penetration and stuff as long as its not cold weld, just run a straight weld in line with axis of the shaft because that minimises the error that can come after the weld expand and shrink.
    Like others sugested machine the worn surface before welding.
    Clean between the pases with angle grinder and wire wheel to be sure you dont get any porosty
     
  7. 8ob

    8ob Forum Supporter

    Messages:
    6,678
    Location:
    moscow on thames
    Can't think of the brand name, it comes on a roll. Brammer (BSL) stock it. It squashes down to size and has quite a scope.

    Bob


    [​IMG]
     
    slim_boy_fat and nickk like this.
  8. jsf55

    jsf55 Forum Supporter

    Messages:
    698
    Location:
    Sunny Swansea
    Loctite bearing fit ? i've seen some pretty loose bearings work well with it
     
    Hopefuldave likes this.
  9. optima21 Forum Supporter

    Messages:
    3,083
    Location:
    halifax, England
    slim_boy_fat, 8ob and Agroshield like this.
  10. Pete.

    Pete. Member

    Messages:
    9,808
    Location:
    Kent, UK
    John Stevenson put up quite a few pics of motor shaft repairs on various forums. He just welded them up, then put a steady rest on the bearing race to get the rotor running true and re-cut the centre. Once he had the centre re-established it was a simple lathe turnng job to get the shaft back to size.
     
    phm87 likes this.
  11. Agroshield Member

    Messages:
    1,364
    Just wanted to say thanks for that link. Lots of useful technical info. there.

    I think it would be correct to say that the shaft still requires machining true before one of these can be used. Also, it might be important not to have a square-edged groove as it will be a stress riser.
     
    optima21 likes this.
  12. hermetic

    hermetic Member

    Messages:
    187
    Yorkshire UK
    You could get it metal sprayed, that was our go to repair system for motor shafts that were considered "beyond loctite"
     
    Hopefuldave, arther dailey and jsf55 like this.
  13. Agroshield Member

    Messages:
    1,364
    The OP's shaft is worn where the bearing itself sits so he needs an alternative place for the steady or cathead. JS used to repair boogered keyways and the like and I believe just used standard MIG wire.
     
  14. Pete.

    Pete. Member

    Messages:
    9,808
    Location:
    Kent, UK
    Oh, in that case use a speedi sleeve. Easy fix.
     
  15. brightspark

    brightspark Member

    Messages:
    31,668
    Location:
    yarm stockton on tees
    or make your own sleeve if u can be bothered depending on price
     
    mtt.tr likes this.
  16. arther dailey

    arther dailey Member

    Messages:
    4,120
    Location:
    England
    used to be metal spray on motor shafts back in the day , I think turning shaft down parallel before repair what ever you use is the way to go , weld and turn or those bits @8ob described and loctite would be sound.
     
    Hopefuldave, slim_boy_fat and 8ob like this.
  17. 8ob

    8ob Forum Supporter

    Messages:
    6,678
    Location:
    moscow on thames
    The tolerance rings work well, we have used them on shafts and inside knobbed bearing housings.

    Bob
     
  18. johnser

    johnser Member

    Messages:
    2,113
    Location:
    North Cornwall
    There's plenty of unworn shaft to dti/use as a reference for getting it true.

    Will phone up a supplier next week (can't find any online ones to do it today) and see of I can get something appropriate.

    If so, should be able to turn down the shaft to fit the ring and if it all goes wrong, can always try a weld repair.

    Should also check the housing too!

    This is all presuming I can wrangle it into the lathe.

    Thank for the help guys
     
  19. arther dailey

    arther dailey Member

    Messages:
    4,120
    Location:
    England
    dont forget while at the bearing shop to buy the various bearing fit etc loctites , as they are always handy to have at hand.
     
    Hopefuldave and slim_boy_fat like this.
  20. slim_boy_fat

    slim_boy_fat Forum Supporter

    This a great place, a number of viable solutions offered - never fail to learn something new to be filed away for future use, should I find myself struggling with a job or technique. :hug:
     
    Turbo, arther dailey, galooph and 3 others like this.
Advertisements