Need help with understanding old MAS SN20A lathe
Close
Login to Your Account
Results 1 to 10 of 10
  1. #1
    Join Date
    Jan 2018
    Country
    ICELAND
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default Need help with understanding old MAS SN20A lathe

    Hi.

    I just recently bought an old Lathe Mas SN20A and i am having problems setting the lathe for thread cutting.

    the problem is that i have never worked on a old lathe only modern ones and it seems that i need to chance
    gearing for desired TPI or MM/thread.

    Can someone help me understand this chart, the manual is in Czech and is not helping very much.

    Shared album - Elfar logason - Google Photos

  2. #2
    Join Date
    Dec 2012
    Country
    AUSTRALIA
    Posts
    378
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    82

    Default

    The manual may be in Czech,but it appears the leadscrew is in what we call Imperial,but in east europe is called Whitworth.....ie TPI.......for metric you need conversion gear of 127 teeth,a dead giveaway......anyhoo....change gears are indicated,and if you dont have a set of these,its not good......the basic for imp threads is 60/90/60 on the quadrant......for metric threads you need many different gears (see thread chart) and the said 127 tooth metric translation gear..........simply ..yes,you need change gears....

  3. #3
    Join Date
    Jan 2018
    Country
    ICELAND
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default

    Thanx for the answer John,

    I went and looked at this a bit more and i found all the gears in a tray under the lathe, and then it started to make sens
    it seems that i can thread most of whitwort threads with the basic gears but when to thread MM i will have to change gears for every pitch that i want

    One thing more i am having problem getting the backplate off from the spindle it seems to be threaded one but it is quite stuck, do you have any advise on how to get
    it off ?

    Thanx

  4. #4
    Join Date
    Jul 2004
    Location
    Houston, TX USA
    Posts
    27,210
    Post Thanks / Like

    Default

    Spindle nose (shown in link) is "L" or long taper type. Left of chuck (or back plate) should be a notched (for hook spanner) ring nut - this is screwed onto chuck

    To get it off, the top of the ring nut is turned AWAY from you (your position assumed to be normal operator position)

    When the nut is off the chuck the chuck may need some mild blows with a dead blow hammer to get it off the keyed taper

  5. #5
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    10,377
    Post Thanks / Like
    Likes (Given)
    5843
    Likes (Received)
    4579

    Default

    Quote Originally Posted by Elfarloga View Post
    Hi.

    I just recently bought an old Lathe Mas SN20A and i am having problems setting the lathe for thread cutting.

    the problem is that i have never worked on a old lathe only modern ones and it seems that i need to chance
    gearing for desired TPI or MM/thread.

    Can someone help me understand this chart, the manual is in Czech and is not helping very much.

    Shared album - Elfar logason - Google Photos
    Seems a right decent lathe. Metric is bound to be a factor in Iceland.

    Suggest you cheat. Avoid single-pointing Metric threads altogether.

    A) Rig a holder than can keep a common hand die true, gently use lathe's power to run it. Work nor lathe won't care if Metric, US, or Elte Englisch. Taps, are, easier, of course. So is measurement - you'll get "standard" sizes as an automagical byproduct.

    B) When that just CANNOT work, take the part to someone who has an all-Metric lathe for threading. At least the distance of any such trip is likely to be short in Iceland.


  6. #6
    Join Date
    Dec 2012
    Country
    AUSTRALIA
    Posts
    378
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    82

    Default

    If you must cut metric threads with a tool,note that you cannot use the "thread dial" mounted to the saddle.......this dial only works with inch threads because the leadscrew is also an "inch "thread......probably 2TPI or 4TPI........to cut metric threads the halfnut must be left alone and the lathe reversed,after backing out the tool,of course.......so it is obvious that your machine is made for the English market,where a great number of TOS machines were sold.

  7. #7
    Join Date
    Jan 2018
    Country
    ICELAND
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default


    B) When that just CANNOT work, take the part to someone who has an all-Metric lathe for threading. At least the distance of any such trip is likely to be short in Iceland.

    You would be surprised how much distances are here in Iceland you cannot skip having a car here

    Thank you for all of your input, great advice´s here

    I must have a special or older version because mine has a threaded back plate and no nut to release the plate

    I have a picture but a bad one will take better tonight
    Shared album - Elfar logason - Google Photos

  8. #8
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    10,377
    Post Thanks / Like
    Likes (Given)
    5843
    Likes (Received)
    4579

    Default

    Quote Originally Posted by Elfarloga View Post
    You would be surprised how much distances are here in Iceland you cannot skip having a car here
    Only because you have a rather slender public trans system. I HAVE driven rather a lot of "Island", and more than once. Usually based Hotel Esja, but rented the cars at the airport.

    Point being the "other" manual, metric, lathes will probably be right in Reykjavik and near the (remains of) the fishing fleet doing repair work. Or mayhap out at that aluminium production facility (still there? I have a couple items of "Look!" cookware left) also doing repair work.

  9. #9
    Join Date
    Jan 2018
    Country
    ICELAND
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default

    Well distances aren´t the problem, just that i don´t like to have a tool that does not work so i fix it. but if i would have to chose, driving 60km vs changing a gear set
    changing a gear set would be the winner any time.

    and i have access to other lathes at work that is no problem.

    yes the aluminum plant is still running, so are the silicon plants. i am working as a engineer at one of those plants.


    but back to the back plate !

    here is a better picture, is there no special trick to get it off ?

    Shared album - Elfar logason - Google Photos

  10. #10
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    10,377
    Post Thanks / Like
    Likes (Given)
    5843
    Likes (Received)
    4579

    Default

    Quote Originally Posted by Elfarloga View Post
    Well distances aren´t the problem, just that i don´t like to have a tool that does not work so i fix it. but if i would have to chose, driving 60km vs changing a gear set changing a gear set would be the winner any time.
    My "fix" to a 10EE being inch-only was to add an HBX-360-BC. AND NOT plan to use its "Witworth" AKA "Inch" threading anyway.

    I'd rather have ALL of lathe hold to a single measurement-system "race", cross-feed dials, compound, still-functional thread-dial (or the Cazaneuve divergence therefrom).


    but back to the back plate !

    here is a better picture, is there no special trick to get it off ?
    LOOKS to be a simple thread-on style.

    "Trick" was to use salvaged belting or a strip of rubber and common rope twisted to a tournequet to restrict spindle rotation without damaging gearing, then.. place a length of Oak in/across the jaws and give it a sharp downward-at-operator's side (counterclockwise, IOW) whack with a hammer.

    If No Joy?

    See if you can separate chuck from backplate in situ.

    Unlikely, but not impossible, that there are DIN/Sov Block equivalent of an "A" short-taper facebolts under it.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •