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  1. #1
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    Cool 3 start, 4 pitch stub thread info needed.

    I 'm looking to thread an internal 4 pitch, 3 start stub acme, 1 1/8 OD. What should be my minor dia?
    I also never came across a stub acme. Need info on my lathe set up.

    Jay

  2. #2
    Limy Sami is offline Diamond
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    There's quite a bit of it

    MHB 27 page # 1843

  3. #3
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    Quote Originally Posted by Limy Sami View Post
    There's quite a bit of it

    MHB 27 page # 1843

    That would be too easy

  4. #4
    Limy Sami is offline Diamond
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    Not quite sure what you meant there J,.. no MHB to hand?

    anyway;-

    Acme Thread-Inch En

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    Limy..you da man. Now how would I set it up for 3 starts. From the quick glance..it looks like the stub is just shorter? or is the form of the tool different from a standard acme?

    Jay

  6. #6
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    Hows about #23?


    -------

    Think Snow Eh!
    Ox

  7. #7
    Limy Sami is offline Diamond
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    Quote Originally Posted by JB @ C and L Machine View Post
    Limy..you da man. Now how would I set it up for 3 starts. From the quick glance..it looks like the stub is just shorter? or is the form of the tool different from a standard acme?

    Jay
    Think the setting up bone has been well chewed here.

    need help on double start threads

    Dunno about thread form etc IIRC I've never knowingly cut a stub acme.

  8. #8
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    Quote Originally Posted by Ox View Post
    Hows about #23?


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    Ox
    ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????

  9. #9
    429FORD is offline Aluminum
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    Formula for thread depth on a stub acme is 0.3 X pitch (in decimals)
    + 0.01. You must use a four pitch stub acme insert.

    Ford

  10. #10
    SND
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    4pitch, 3 start, so a lead of 1.33333~? if I get this right. Got a cnc? I doubt I'd have any fun trying to gear that one in an regular manual lathe Would also require a tool with a lot of front clearance as its a fast lead, not sure a regular insert could have enough clearance added to it.


    Or is it 3 start, with a lead of .25? using a 12tpi tool, but lathe set at 4tpi? should be easy enough to tell that one by eye if you have a sample/worn out one?

    I haven't cut multi starts in probably 7years, I kinda forget.

    Anyway, for picking the engagement points, I find it easiest to just set the compound at 90 aka parallel to the ways, advance the require amount for the next start. Which means you have to plunge cut with cross slide only. Leave the half nut nut engaged. Works better in some materials than others.

  11. #11
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    I don't have MHB #27, but I have #23.

    Just wonderin' if he would post that page too.



    And BTW - Thanks for buggering up the page!




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    Ox

  12. #12
    Gary E is offline Diamond
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    In MHB 16th EDITION.... Stub Acme's start on page 1173

    Anybody got an older edition??

  13. #13
    Limy Sami is offline Diamond
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    Quote Originally Posted by Gary E View Post
    In MHB 16th EDITION.... Stub Acme's start on page 1173

    Anybody got an older edition??
    See your 16th and raise you my 9th ......... but no mention of stub acme.

    Sorry OX haven't got #23

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    Quote Originally Posted by Ox View Post
    I don't have MHB #27, but I have #23.

    Just wonderin' if he would post that page too.



    And BTW - Thanks for buggering up the page!




    -------------

    Think Snow Eh!
    Ox

    What do u mean?????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ???

  15. #15
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    The print date is 1961..so somebody had to cut it manually. I dont see a 1 1/3 on my lil ole b-ham..so............

  16. #16
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    So, you are going to have to calculate a gear train to be added to the left side of your quick-change gearbox (QCGB) Not all lathes have provisions to do this, but many do. You usually have to buy some change gears from Boston Gear or Martin Sprocket.

    A complete tutorial of how to do this would be quite a job of writing - and I might add that I've never actually added any gears to the left of a QCGB.

    The place to start is to know the specifications of the gears on the left side of the headstock: Their diametral pitch, pressure angle, width, and what kind of bores they have, both size and description of keyways. (You cannot expect even the most experienced gearmaking firms to know the specs for every lathe.)

    Then you need to know the pitch of the leadscrew.

    Then you can research calculating a gear train. Believe me, it ain't that hard !!!

    Really odd pitches like this are the only time that a person might be grateful to have an old "loose change gear" lathe without a QCGB.

    And, for Pete's sake, go to eBay or AbeBooks.com or something and buy yourself a used copy of Machinery's Handbook (MH). You are talking about undertaking a rather advanced threading task. Persons doing such work need basic references like MH. There is so much information in an MH it's incredible - not just tables, but also general info about many tasks.

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