Messed Up My SB Lathe
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  1. #1
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    Default Messed Up My SB Lathe

    Hey All,


    New to your forum. I needs some help and advice. This morning I made the fatal error of moving gears while my lathe was still just moving... BANG! a few choice words after that, I knew I screwed up.
    Pulled the cover off the left side and found I had sheared a few teeth off a gear. Not sure what this gear is called so I posted a couple of pictures.
    Is it possible to find this piece? It's Sunday so I will call SB tomorrow, I think it's a Government unit, S/N 105631. No letters, they will most likely tell me nothing.

    Dimension are; Center hole 1.1225". Outside Dia. 4.190. & .5" thick. The smaller gear was pressed in and not damaged.

    I sure would appreciate any help at all, I really enjoy this lathe. Owning it for well over 20 years I just can't believe I did what I did.

    Thanks guys,

    Chris Campbell
    Attached Thumbnails Attached Thumbnails img_3391.jpg   img_3390.jpg  

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    What model lathe? Gears were different for different lathes.

    Don't call South Bend, call Boston Gear - that gear was replaced years ago.

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    My best guess would be this gear on Amazon.

    You'll have to bore it to size and press the small gear in. They both should be pinned together and not rely on the press to hold them together.

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    I wish I knew the model, It has a 13" swing that is what makes me think it's government, that and the green color.

    Thanks so much for your help.

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    That looks really promising!! Pin for sure. Seriously you made my day.

    Thanks, Chris

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    You need to know the Diametral Pitch (DP) of your gear. DP is number of teeth + 2 divided by the outside diameter (OD).

    DP= (N+2)/OD

    If you recheck the OD of the gear and find it closer to 4.125", then your DP is 16, like that in the link.

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    Quote Originally Posted by SLK001 View Post
    You need to know the Diametral Pitch (DP) of your gear. DP is number of teeth + 2 divided by the outside diameter (OD).

    DP= (N+2)/OD

    If you recheck the OD of the gear and find it closer to 4.125", then your DP is 16, like that in the link.
    Just ran over to the shop it's a 4.25" outside diameter.

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    Dang it yes it is 1.125!! man this has been a crazy day.

    Thanks so much for your advice & Help.

    Chris

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    Quote Originally Posted by Chris Campbell View Post
    Dang it yes it is 1.125!! man this has been a crazy day.

    Thanks so much for your advice & Help.

    Chris
    I think you better check again. Perhaps you measured the wrong gear?

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    Quote Originally Posted by SLK001 View Post
    I think you better check again. Perhaps you measured the wrong gear?
    LOL Well yesterday was a bad day. yes it is 4.125" The last Gear they had I ordered.

    Chris

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    My old BG catalog confirms you did good

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    If the lathe is old, it will have gears with a 14.5deg pressure angle. Newer gears have 20deg pressure angles.

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    It's old, not sure how old but it works great. literally built all my suspension bushings for a formula ford now building parts for a land speed roadster. Really makes you feel good to build stuff on an old loose machine.
    Gear should be here tomorrow, I have a friend with a 10" SB. He has a large chuck that we can bore the center out.


    Chris

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    Bore it to a light press fit. Too much pressure will crack a cast iron gear. Then, drill a hole the size of your pin right on the line where the two gears meet and pin the two together.

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    Quote Originally Posted by SLK001 View Post
    Bore it to a light press fit. Too much pressure will crack a cast iron gear. Then, drill a hole the size of your pin right on the line where the two gears meet and pin the two together.
    img_3424.jpg

    Works perfect. I hung the old busted gear right above the lathe... Just a reminder :-)

    Thank you so much for all your advice and help,
    Chris

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    Quote Originally Posted by Chris Campbell View Post
    Works perfect. I hung the old busted gear right above the lathe... Just a reminder :-)

    Thank you so much for all your advice and help,
    Chris
    Good job getting things back in order. I don't see a pin. Is it a roll pin and I am only seeing edges?

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    Sure looks like a flathead set screw to me?

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    Quote Originally Posted by kitno455 View Post
    Sure looks like a flathead set screw to me?
    Good eyes! I see it now under uber magnification.

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    Bad things happen...Good having a machine that parts can be found...

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    Wall of shame reminder right at the tool is a good approach.

    I should take some bent valves and make a totem to hang from my son's BMW 5 series...

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