Cutting heavy threads what size lathe
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  1. #1
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    Default Cutting heavy threads what size lathe

    I have been cutting a few cable tool taper threads on my old l&s and anything courser than about 7 threads per inch i start having issues. Im just doing my own work, swabbs subs thread adaptors stuff like that. There is a early 50s 20” monarch within a days drive and im wondering if that would be heavy enough to cut an api or an if thread without huge amounts of playing with the cutters. this is for personal use and will not be used in stuff that requires certs. And if not what size of lathe swing should i start looking for?

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    What model Monarch? I've owned just about every Model, The NN is the heaviest duty in the 50 vintage. Most 50's vintage lathes are very good! Monarch will probably be expensive, it has name recognition. Reid Prentice will be good too.
    What diameter are you threading?

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    Quote Originally Posted by idacal View Post
    I have been cutting a few cable tool taper threads on my old l&s and anything courser than about 7 threads per inch i start having issues. Im just doing my own work, swabbs subs thread adaptors stuff like that. There is a early 50s 20” monarch within a days drive and im wondering if that would be heavy enough to cut an api or an if thread without huge amounts of playing with the cutters. this is for personal use and will not be used in stuff that requires certs. And if not what size of lathe swing should i start looking for?

    I'm not sure "lathe swing" is a good indicator for your application.
    Yes often a larger lathe is better suited. But consider a larger swing adds length to all of the components potentially lowering overall torsional stiffness of the lathe.

    Swing can be an indicator. But machine weight/design is the real tell tail for rigidity. A machine of the same weight half the swing/length with be loads stiffer than a bean pole budget large swing lathe.
    With an API form cutter you have lots of cutter contact when cresting the thread, that required more pressure Argo a stiffer lathe to not chatter.

    Had a friend with a 26" swing 80 length 6" bore cnc lathe (flatbed style). Had lots of troubles cuttin API threads on short subs. Switched to a 3" bore 10" swing 18"z slant bed that weighted the same and it absolutely destroyed the other in performance.

    Not saying you need a fancy cnc, but it is a good example

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    All sorts of work-arounds - like Sub Head Stocks (6:1 reduction)

    The trick of course was SLOW

    Thumbnail from 1940 Hendey Manual

    One has to understand this was before folks assumed it was impossible to do anything without the exactly right insert they could "buy"

    In other words, part of the work around was doing one flank, and then the other - with whatever cutting tool(s) that worked well for this piecemeal approach
    Attached Thumbnails Attached Thumbnails page-57.jpg  

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    Quote Originally Posted by johnoder View Post
    All sorts of work-arounds - like Sub Head Stocks (6:1 reduction)
    Hi John,
    How common were Sub Head Stocks? I don't believe I've ever seen one, but I've never spent time in heavy-part shops.

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    I suppose fairly common

    Hendey, ATW, L&S, Monarch, P&W , etc. all sold them. Doubtless others also

    Thumbnail is P&W's additional equipment page showing their version

    Note on page 3 here that Monarch listed them as accessory equipment for Tool Room lathe

    http://vintagemachinery.org/pubs/2103/17533.pdf

    ATW's subhead covered on page 28 and 29 here

    http://pounceatron.dreamhosters.com/...-5-1937-si.pdf
    Attached Thumbnails Attached Thumbnails additional-equip-scan_3.jpg  
    Last edited by johnoder; 04-08-2019 at 04:59 PM.

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    im not sure what model yet i am trying to get the serial number, but its a 20" swing the biggest thing I would try to thread would be 8" stock maybe some hydraulic barrels bigger than that but those are a lot easier threading project.

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    Quote Originally Posted by johnoder View Post
    I suppose fairly common
    I discussed this in another thread. Maybe they were common I don't know, but it took me 3 years to find the one I've got and I had to buy a whole lathe along with it to get it. I wonder if they were often tossed out even the people who have one generally don't know what it is.

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    part of the work around was doing one flank, and then the other
    Yes, with large threads and acme I do this a lot, and have even used wear offsets to get around chatter on longer shafts in the CNC. It's the actual length of the cutting face that causes chatter (With other problems included) and moving the cutting edge in and out and side to side is one slow but sure answer, over cutting with the whole edge.

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    Quote Originally Posted by idacal View Post
    I have been cutting a few cable tool taper threads on my old l&s and anything courser than about 7 threads per inch i start having issues. Im just doing my own work, swabbs subs thread adaptors stuff like that. There is a early 50s 20” monarch within a days drive and im wondering if that would be heavy enough to cut an api or an if thread without huge amounts of playing with the cutters. this is for personal use and will not be used in stuff that requires certs. And if not what size of lathe swing should i start looking for?
    I have turned 4 TPI internal threads on antique 11x24 Kerry so with 20" Monarch it should be a piece of cake.

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    Here is a sturdy L&S Powerturn they are about giving away - you can get something long enough to really stay still with those big four jaws on both ends of spindle

    LATHE LODGE & SHIPLEY - tools - by owner - sale

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    I ended up buying it now I have to go pick it up and see if I bought a lemon, its a early 1950s 20 by 150 and Im trying to get a rough weight any ideas

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    Quote Originally Posted by idacal View Post
    I ended up buying it now I have to go pick it up and see if I bought a lemon, its a early 1950s 20 by 150 and Im trying to get a rough weight any ideas
    Could be an M, so 22 1/2 Actual. These are over 10K with 48" centers - length additions are 600 for each two feet

    http://vintagemachinery.org/pubs/2103/19752.pdf

    Could ALSO be 20" C - considerably less iron

    Here is an 18" C - which was 20 1/2" actual - 5700 for 48" centers and only 350 for each extra two feet of length

    http://vintagemachinery.org/pubs/2103/17534.pdf

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    it looks like a series 61 , pictures are kind of blurry, Im picking it up next week will get better pictures when i get it. found the broachur on it looks like about 13000
    according to vintage machinery thanks for that link johnoder
    may be a total waste of money and time but I will see.


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