cast iron or steel - gears on an old lathe
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  1. #1
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    Default cast iron or steel - gears on an old lathe

    Hello,

    I am not at a shop for a long while but need to oversee replacing a couple gears on an old (very old) Southbend lathe.

    20200113_121221.jpg

    20200113_121147.jpg

    lathe.jpg

    I did a lot of looking around, and have some experience with spark tests, etc. - cast iron vs cast steel id - but I also am not sure anyone back at the shop is. That said, I guess there is a little uncertainty between these tests... I wouldn't say these gears "ring" when I hang them by a rope and hit them, but they also do not "thud".

    So rather than repeat all the good answers in the above link, I thought I would just ask if people knew for sure what material Southbend used for their gears, say before the late 40s - I really don't know its age because Grizzly could not find my lathe in their "catalog", the # stamped in the bed is 44560 - pretty small; catalog #: 394-H. From southbend's website;

    The earliest records show that lathes were numbered sequentially, beginning with 700, in July, 1910, and ending with 186,514 March, 1947.
    Thank you for any advice and hope it is appropriate to ask...

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    Based on the fracture of the broken teeth, the texture of the un-machined surface, and my old South Bend, I'd say they're cast.

    I'd also say it doesn't matter. What you need to match (other than the obvious tooth count) is pitch and pressure angle.

    There is a wealth of information in the South Bend sub-forum here and on Steve Wells' website The SBL Workshop

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    Okay, thank you for the links - I will look at them now. By the way, yes, they are 14.5 PA, 10DP, 64 & 66 T. I already have them drawn up for bids from several small volume manufacturers... it's just that many are pushing steel and I'm worried about the existing gears on the lathe that will mesh up to the new gears. Did you mean cast ductile iron?

    Thanks!

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    Ductile iron was patented in 1949. It was first developed in 1943 but the process to make it reliably was patented in 1949. Not in an old Southbend

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    You could make them out of steel, cast iron or ductile iron and any of the three would be ok in that application.

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    Thank you for those! I did see many places where I could get similar gears, but for the same price I can get them made to the same face width (~1.13), ID and keyways. I know its not a big deal, but it will be hard enough to know that they aren't original I'm keeping the old ones for when I get the courage, or money, to repair them. But thanks again!

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    Well, the gears that these interface with are more "complicated", in that they seem to have a machined, extended hub. Not a big deal, but definitely more money and/or time to work on than these simple spur gears. That's why I wanted to match the material.

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    Quote Originally Posted by Dan from Oakland View Post
    You could make them out of steel, cast iron or ductile iron and any of the three would be ok in that application.
    You could make them out of bronze and it'd be okay

    That's probably why people are suggesting steel - just cut the blanks out of a plate or maybe they have some big round bar. Easier than making a hole in the sandbox and melting up some iron to pour in. Agree with Dan steel will work fine.

    But bronze would look nicer

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    I cast grey iron camelback straight edges on average once a week. From the grain pattern of the break, the vintage of the machine and the general appearance of the gear castings, I think they are almost certainly grey cast iron. If you decide to cast blanks, have your foundry pour ductile iron. It won’t fracture like grey does.

    Denis

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    If you used Aluminum gears they would be consumed and preserve the original gears. Bronze would be slightly better but the cost is not worth it.

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    And so you will know, 394H is an 18" Series O from 1934 - quite a hefty beast for a SB

    Catalog 94 on Mr. Wells web page, page 4

    Most assuredly gray cast iron, maybe class 30, per ASTM A 48 - not that the lathe would care after 86 years

    Hope you have the "banjo" missing in the photos

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    [QUOTE=b.rett;3475722]Hello,
    I am not at a shop for a long while but need to oversee replacing a couple gears on an old (very old) Southbend lathe.

    Not for nothing, but those gears can be easily repaired by slotting the areas under the missing teeth, silver soldering in
    1018 steel blanks, and then using an involute cutter to profile the blanks. A repair like that has the advantages that
    a) will be stronger than the original tooth, and b) retains the majority of the original part. Back in the day repairs were
    often done with pins pressed in:






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    And to follow on Jims'



    ph

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    Quote Originally Posted by b.rett View Post
    Thank you for those! I did see many places where I could get similar gears, but for the same price I can get them made to the same face width (~1.13), ID and keyways. I know its not a big deal, but it will be hard enough to know that they aren't original I'm keeping the old ones for when I get the courage, or money, to repair them. But thanks again!
    Make sure the ones you order to make are hobbed Otherwise you better buy it from one of those places
    Peter

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    I don't know where in Texas your are located in, Durabar Metal services (Formally Lokey Metal Services) in Ft Worth can provide you with either G-2 Gray Iron or 80-55-06 Ductile Iron slugs for making gears out of. Ken

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    malleable cast iron been around for about 2000 years
    .
    Malleable iron - Wikipedia

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    Quote Originally Posted by DMF_TomB View Post
    malleable cast iron been around for about 2000 years
    .
    Malleable iron - Wikipedia
    The difference between malleable iron and ductile iron: https://www.hunker.com/13401251/diff...malleable-iron

    "Properties


    Metal workers can draw out a 2-inch test sample of ductile iron by 18 to 30 percent more than its original length. By contrast, malleable iron elongates by only 10 percent. Ductile iron has a higher "yield strength" than malleable iron, meaning it can bear greater loads and higher temperatures. However, according to the Kirkpatrick foundry, malleable iron is the best choice when you want to cast thin sections or plates."

    Denis




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    malleable iron is heat treated cast iron. Chinese had it easily 2000 years ago.
    .
    belt buckles, , pipe fittings, C clamps and many many other items were made from malleable iron long before ductile iron was invented discovered. even regular grey cast iron comes in different grades. the stronger it is the harder to machine.
    .
    lathe gears hard to say what made out off. i have seen zamak or zinc aluminum alloys too. even seen plastic gears on really cheap stuff. of course a high strength heat treated steel is sometimes used for gears too

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    We manufacture thousands of new change gears annually. Both as specials and sets for machines we build. For typical applications gray iron bar is ideal. If using steel, gears must have lubrication.


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