SB Lathe Repair Needed (Help)
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    Default SB Lathe Repair Needed (Help)

    Hi,
    My 1941 13" SB Lathe counter-shaft is shot. The bearings are cast iron. There must be 0.030" slop and the shaft is badly scared. I'm thinking to over-bore the bearings, 4-step belt-sheave and V-belt sheave to 1-3/16" and make a new shaft. Another option would be to overbore the cast iron and press in bronze bushings.

    I don't have the tools to do this. So I'm looking for a machinist in SoCal to help. I like to find if anybody has any recommendations.

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    No need to overbore the cone pulley if you just step down the ID of the new bushings/bearings out at the ends.

    I’d go with rubber sealed bearings if the pivoting base plate casting ears have enough material to do so. You don’t want to be working down under there for lubrication very often.

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    The later models used radial bearings to support the shaft. I don't think there is enough metal to put a set in that could support the loads.
    I'm concerned if I bore enough to press bronze bushing it that the cast iron will be too thin.

    Thanks!
    Quote Originally Posted by thomasutley View Post
    No need to overbore the cone pulley if you just step down the ID of the new bushings/bearings out at the ends.

    I’d go with rubber sealed bearings if the pivoting base plate casting ears have enough material to do so. You don’t want to be working down under there for lubrication very often.

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    Valid concern; however, you’ll be surprised how many parts on our old SB lathes were made from 12L14 stock or something very similar to it.

    You may find a smaller OD in modern 4140 or 1144 material will get the job done without reinventing the wheel too much using total loss bronze bearing lube.

    Good luck getting her running. BTW, Halligan142 recently rebuilt a cast iron oil slinger type underdrive on his YouTube channel for his pre-war 13”. Some good content there.

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    One option, although the machine won't be original if that matters to you, is to fabricate a frame out of angle iron and mount some pillow block bearings on it with a new piece of cold roll and replace the whole assembly. This is actually what I did on my 15" SB about 40 years ago, because I had no other equipment to do anything else and no one with a machine shop to do the work for me. It's still working fine today, but again, the machine is not original. But, that matters very little to me. It's a nice lathe and does good work. That's what is important to me.

    You could even keep the original stuff and fix it later on. You'll have a running lathe to do so if you chose.

    YMMV,
    Ted

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    Tom, would know but it seems like if you have to do it a cylindrical needle bearing might be an excellent option...most 1.125" bore ones have an OD of 1.375"....

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    Like this-

    Koyo NRB - B-1812 - Motion Industries

    Common,cheap,and easily replaceable....pack em with grease and add lip seals, never touch them again...also available in narrower widths if that's too wide.

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    Quote Originally Posted by thomasutley View Post
    No need to overbore the cone pulley if you just step down the ID of the new bushings/bearings out at the ends.

    I’d go with rubber sealed bearings if the pivoting base plate casting ears have enough material to do so. You don’t want to be working down under there for lubrication very often.
    If the shaft has centers then turn between centers to the next sealed bearing size likely to last 60 years or more..
    bronze bushings also a good idea.

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    The needle-roller bearings seem like a good idea. I wonder if the stock oiling systems would work? That is a oil reserve and a loose ring/slinger riding on the shaft.
    Secondly - would the shaft need to be hardened to successful on the bearings?

    Replacing the bearings may be easy, but getting the assembly out of the lathe is difficult.

    Thanks.

    Quote Originally Posted by iwananew10K View Post
    Like this-

    Koyo NRB - B-1812 - Motion Industries

    Common,cheap,and easily replaceable....pack em with grease and add lip seals, never touch them again...also available in narrower widths if that's too wide.

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    I like your suggestion. I have no access other machinery to make the repairs. So I'd need to farm it out. I had to have a pinion shaft made for the gear box and that cost twice what I paid for the whole machine. If I cannot find someone to bore the bearings for me at cost within my budget then I'll give your recommendation a go. I especially like pillow block bearings they will last me forever with little maintenance.

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    Coming up with a plan it seems that a PM guy, a local hobby lathe guy, or even a machine shop could help you out.
    Anything in the ebay photos to help tell what you need?
    Lathe Countershaft | eBay

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    In case you do go the pillow block route, here are pictures of my ~40 year old fix. Works great. Made a angle iron frame for the pillow blocks, shaft and bottom cone pulley and a flat mounting plate for the motor. It's kind of hard getting good pictures down there though...

    Ted

    sb-1.jpg
    sb-2.jpg
    sb-3.jpg

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    Or,bail out for a later model? (They seem to have a couple 13s)...sell off old one and break even.
    South bend lathe - heavy equipment - by owner - sale

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    I have a early 50's SB 13" I'm parting out, and I'm in Sun Valley. PM me and we can get together...

    John

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    I started shopping for materials to fabricate a new underdrive. I was surprised to find pillow block bearings cost $100 ea.

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    The machine John is parting out likely has the ball bearing countershaft.

    No way I'd try to fab up a replacement when one can be had.

    That or I'd go and check out that rusty late model 13 in the link I put up.
    That's a hard bed,double tumbler,lever clutch,large dal machine...it's cheap and rust usually just wipes off and what doesn't can be pushed off with a razor blade.

    Play your cards right and you can break even easy by parting out your old one.

    Lot of options....

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    Quote Originally Posted by jvaliensi View Post
    I started shopping for materials to fabricate a new underdrive. I was surprised to find pillow block bearings cost $100 ea.
    You are looking in the wrong place: Surplus Center

    That said- I would buy the ball bearing underdrive unit from a later lathe before I would make one.

    allan

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    Hi,
    I've been think to ditch the counter-shaft and direct drive the lathe from the motor. I would use a VFD for speed control.

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    Quote Originally Posted by jvaliensi View Post
    Hi,
    I've been think to ditch the counter-shaft and direct drive the lathe from the motor. I would use a VFD for speed control.
    I recommend VFDs, but you will find that in direct drive they don't produce enough HP at low speeds to remove metal, unless you oversize the motor. You need to keep the mechanical reduction of the countershaft.

    comstockfriend posted in this thread that he has one for sale, which likely has replaceable ball bearings. BUY IT.

    allan

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    Yeah, you CAN ditch the countershaft BUT then you need to design a drive system from the ground up....it doesn't work out well to just "go direct"
    BTDT..

    It can be done, but takes substantial work to pull it off....and the motors suited are very expensive unless you find a real good deal.

    See if you can score the countershaft from the machine John is selling.


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