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Thread: Lathe restoration SN20

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    TexBuxer's Avatar
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    Lathe restoration SN20

    I bought old lathe. brand is MAS/TOS, type SN20. Made in Czech Republic. Age is about 50 years, and it's been unused for last 20. It needs major rebuild and cleaning. Nothing is really broken, some wear and heavy dirt. I've been looking for manuals and pictures, but I have found only old manual copied with camera, in original language so not very useful. I need tables for levers, because oil has dissolved markings. If anyone could help, that would be great.

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    Right off, I'd google for images of that model. Is the machine graduated metric or imperial? Equipment seemingly not so prevalent on one continent can be prominent elsewhere.
    1] Count gear teeth outside the headstock, pitch of lead screw, and mark them with a paint pen.
    2] Overall, you'll be more interested in feed and threading plaques than RPM. Feeds can be measured by a protractor and travel indicator, provided you can rotate spindle manually.
    3] There I'd open an excel spreadsheet and place info recorded in cells. Calculations will be just division and multiplication.
    4] Speeds can be determined numerous ways. Depending on electrical supply, Hz and voltage in particular, you can determine via motor tag at your power available.

    I helped generate plaques once in this very process. With all info compiled, spreadsheet was artwork for brass plates to be photo acid etched; fonts, decimals, arrows and all. Brass plates can be thickness of shim stock on up. Surprisingly low cost compared to engraving, and realistic standing figures, vs those in relief. Either can backfill with paint highlighting. There are companies that will cast from a pattern, costly and lesser distinct detailing.
    Sincerely,
    Toolmaker51
    ...we'll learn more by wandering than searching...

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    Quote Originally Posted by Toolmaker51 View Post
    Right off, I'd google for images of that model. Is the machine graduated metric or imperial? Equipment seemingly not so prevalent on one continent can be prominent elsewhere.
    1] Count gear teeth outside the headstock, pitch of lead screw, and mark them with a paint pen.
    2] Overall, you'll be more interested in feed and threading plaques than RPM. Feeds can be measured by a protractor and travel indicator, provided you can rotate spindle manually.
    3] There I'd open an excel spreadsheet and place info recorded in cells. Calculations will be just division and multiplication.
    4] Speeds can be determined numerous ways. Depending on electrical supply, Hz and voltage in particular, you can determine via motor tag at your power available.

    I helped generate plaques once in this very process. With all info compiled, spreadsheet was artwork for brass plates to be photo acid etched; fonts, decimals, arrows and all. Brass plates can be thickness of shim stock on up. Surprisingly low cost compared to engraving, and realistic standing figures, vs those in relief. Either can backfill with paint highlighting. There are companies that will cast from a pattern, costly and lesser distinct detailing.
    Lathe restoration SN20-pict9054.jpg

    I found this, other smaller plates still missing. I'm not going to make full restoration, only functional. I need lathe in my hobbies.

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    Quote Originally Posted by TexBuxer View Post
    I found this, other smaller plates still missing. I'm not going to make full restoration, only functional. I need lathe in my hobbies.
    Click image for larger version. 

Name:	PICT9054.jpg 
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    Call yourself Long John Silver; this is equivalent of a treasure map! Saves you HOURS of counting and calculations.
    What other plates are missing [i.e. where located]?
    Next stop Lathes + Machine Tool Archive a near boundless reference. For other materials, there are many Central Europe contributors on this site, certainly familiar with MAS/TOS and Czech language, etc. Just do internet version of raise your hand.

    With a 1.8" spindle bore, +15" Ø capacity and that RPM range, you have a powerful, serious lathe. Whatever center distance, those specs tell me "shaft lathe". If you have the tailstock, anything else like steady rests are not hard to fabricate. Restoration isn't always very productive, thorough cleaning is. You can go to town on her; a heap of rags, small brushes, light abrasive pads, citrus based hand cleaners , and some Stoddard or kerosene solvent. Lube a gearhead pal or two with a big sub sandwich and bottled elbow grease IYKWIM.

    I haven't run their lathes, but really piled chips with TOS mills in 50 NMTB. I'd say performed well as any better known brands, for lots less moola. Compared to filmy chinesium impressionist abstract machine tools, the eastern bloc built the real deal. Didn't scrimp on iron, fittings or important features, added distinctive attributes, like shifters with positive detents, and best of all real man-sized controls. One of my go-to rants there, ergonomics.

    Another, the lecture why this ain't "just a hobby".
    Last edited by Toolmaker51; 05-27-2018 at 12:38 PM. Reason: duplicate statements [aka copy/paste w/o delete]
    Sincerely,
    Toolmaker51
    ...we'll learn more by wandering than searching...

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    Finding that diagram is like finding the holey grail. TM51 is correct that is a serious machine.
    Full on restorations are always more involved in redoing older machines that it appears at first. In some cases it can be akin to building almost from scratch.
    If none of the gears have been crashed or are not worn too badly just use them as they are after a good clean up replacing bearings would be among the most important part of a rejuvenation replacing detent balls and or springs any worn keys if the ways are badly worn then this will also mean the carriage will be worn as well sometimes a good scraping of the ways will help tremendously but to do it proper the underside of the carriage should be trued then the ways trued This can involve having to completely strip the machine and have the bed trued to match but if only a few .ooo"s then removing the tail stock and truing the ways to be parallel to the spindle bore will be sufficient some tail stocks can be shimmed back to height.
    Many very high precision parts have been made on machines that were nearly completely worn out by by most peoples standards the machinist learns where the discrepancies in his machines are and compensates by altering his machining processes and set ups.
    I've seen machines so loose and worn they rattled or had horrible whining noises but the parts coming off of them would be comparator indication quality.
    Never try to tell me it can't be done
    When I have to paint I use http://kbs.justoldtrucks.com/

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    Lathe is almost 3 meters long, I think span is 2 m. I have tailstock, center support and 3 chucks. No tools yet, or they are in bad condition. I have not tried it yet, power cable is missing and I have car engine swap on progress. I'll get pictures later.

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    Mas SN 20 Lathe

    Quote Originally Posted by TexBuxer View Post
    I bought old lathe. brand is MAS/TOS, type SN20. Made in Czech Republic. Age is about 50 years, and it's been unused for last 20. It needs major rebuild and cleaning. Nothing is really broken, some wear and heavy dirt. I've been looking for manuals and pictures, but I have found only old manual copied with camera, in original language so not very useful. I need tables for levers, because oil has dissolved markings. If anyone could help, that would be great.
    I have also found a MAS SN 20 Lathe in South Africa also needs a rebuild stood outside for 6 months and had the motor and tail stock stolen
    Could possible help with some info
    Regards
    Jonathan

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    Serious stuff, the TOS machines I've seen have been virtually bombproof. One interesting thing I saw on one about ten years ago was that both longitudinal and cross feed could be set at different feeds and both engaged alone or together. I've never seen or heard of anything like this before or after. Owner said it used to be used in making tank parts. I don't know whether this was a special or an option but I thought it was a great idea.

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    Quote Originally Posted by NortonDommi View Post
    Serious stuff, the TOS machines I've seen have been virtually bombproof. One interesting thing I saw on one about ten years ago was that both longitudinal and cross feed could be set at different feeds and both engaged alone or together. I've never seen or heard of anything like this before or after. Owner said it used to be used in making tank parts. I don't know whether this was a special or an option but I thought it was a great idea.
    I used to own a gromematic Dutch built lathe that could run both the cross and the longitudinal feeds Simultaneously by engaging both the lead screw and the feed shaft but not independently adjustable.
    Never try to tell me it can't be done
    When I have to paint I use http://kbs.justoldtrucks.com/

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