# Tool Restorations >  Lathe restoration SN20

## TexBuxer

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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Paul Jones (May 31, 2018),

PJs (May 28, 2018),

Seedtick (May 27, 2018)

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## Toolmaker51

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.

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NortonDommi (May 29, 2018),

Paul Jones (May 31, 2018),

PJs (May 28, 2018),

TexBuxer (May 27, 2018)

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## TexBuxer

> 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.





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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Paul Jones (May 31, 2018),

PJs (May 28, 2018),

Toolmaker51 (May 27, 2018)

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## Toolmaker51

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



 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".

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NortonDommi (May 29, 2018),

Paul Jones (May 31, 2018)

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## Frank S

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.

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NortonDommi (May 29, 2018),

Paul Jones (May 31, 2018),

PJs (May 28, 2018),

TexBuxer (May 27, 2018),

Toolmaker51 (May 27, 2018)

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## TexBuxer

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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## The SA Blacksmith

> 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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PJs (May 28, 2018)

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## TexBuxer

I found manual from Manu?ly obr?b?c?ch stroj? a za??zen? | Stachura.cz

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PJs (May 28, 2018)

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## NortonDommi

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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## Frank S

> 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.

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## NortonDommi

That's very interesting. As said I'd never even heard of anything like this before, I suppose it could have been set up for turning standard tapers much quicker than a taper attachment. Was a pretty sizeable machine though, wouldn't have fitted in my shed : P From memory it could also cut just about every thread in existence and I suspect you needed a special license to operate.

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## thehomeengineer

Hi
I had a TOS lathe wish I never sold it but needed the money as I was buying a house. The clutch went on the lathe and in the UK the 600 Group offer spares for TOS lathes.600 Group PLC - manufacturer and distributor of machine tools, laser marking systems, precision engineered components and mechanical handling & waste management equipment The spares were expensive so had the bits need for the clutch lazer cut.

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## TexBuxer

Here are the pics, it's easier to use postimage.org

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## TexBuxer

How can I remove slide?

I have removed tapered lock piece.



Allen bolt was removed, but I couldn't remove the slide.


Start lever is broken, all shafts go through feeding box. 


If i could remove shafts rear bearing, I maybe could pull feeder mechanism out from back end.

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Seedtick (Dec 11, 2018)

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## Toolmaker51

Pics are a little small...but slide won't move off carriage until nut from cross screw is detached. To withdraw screw, the bearing supporting handle end also has to be freed from housing, it might go to backside, rare on engine lathes. With 'tapered lock piece' [the gib] some side to side clearance should be present. Unless everything is disconnected it'll shake but nothing else.

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## Frank S

Note on the cross slide feed screw handle there appears to be a tapered pin holding it on.
On some models of lathes this handle must be removed then a spacer than a spanner nut then the index dial can be removed. This is where you will probably find 2 allen screws holding the next assembly in place or there will be another pair of nuts on the feed screw and the back dial will be threaded. requiring it to be unscrewed. LeBlond is famous for that little trick. If you have the 2 allen screws remove them and slip the feed handle back in place so you can turn the feed screw just unscrew it out out of the cross slide then the cross slide can be removed I say this as on some lathes the feed nut mounted to the cross slide can only be removed from below Gromatic did this.
Moving on to your trying to remove the side carriage ( gear box) and or the lead screw and feed shaft as well as the start stop shaft You will find spanner nuts on the end of the lead screw behind them will be a thrust bearing. these must be removed to get the bearing housing off of the body of the lathe bed. Additionally on the other end of these shafts on many lathe models there are tapered pins holding them in place Sometimes these pins may have a 1/4 20 nut on them to hold them in place. These pins are dead soft and easily damaged. You can sometimes loosen the nut a couple of turns if there is still any threads sticking out of the nut add a second nut to the stud then tap the pin a few times to loosen it then remove the nuts and remove the pins. then you can remove the various shafts,
If you damage the tapered pins all is not lost as they were used on so many lathes new one can be purchased from a Machine supply store they will need to know the taper the largest diameter and the length of the pin.
If you have these tapered pins and have to drill them out to remove them do so only from the threaded or the small end and take great care not to drill off center.
Once the pins are removed the shafts will slid out.
Good luck with your project repairing these old lathes without a break down sheet is sometimes a challenge in itself just to figure out how they were put together.
Clausing, Lodge & SHiply, Homach, Monarh, Southbend, LeBlond, Atlas Harrison, Gromatic to name just a very few I have worked on all had a few things in common while at the same time all were very different.

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Toolmaker51 (Dec 12, 2018)

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## Frank S

> Pics are a little small...but slide won't move off carriage until nut from cross screw is detached. To withdraw screw, the bearing supporting handle end also has to be freed from housing, it might go to backside, rare on engine lathes. With 'tapered lock piece' [the gib] some side to side clearance should be present. Unless everything is disconnected it'll shake but nothing else.



by clicking on his pictures a couple of times the grow very well.

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## TexBuxer

I got the shaft bearing separated.


bedways are rather worn. I don't know if this restoration is any good.


Is this somekind of thread freeplay adjustment, how should I adjust it?


What material scraper is, how to replace

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## Toolmaker51

TexBuxer;
A lot of the parts have orientation - front/ back, right/ left, up/ down...Use a paint marker. Nice little dots, what you can identify some time later.
Typical cross slide screws have a few adjustments. Get the screw adjustments understood before the slide and gib.
Clean everything first, with solvents, hand cleaner, even old oil; you're dissolving years of build up. Crevices, corners, oil galleries, threads, holes, bearings, seats...Then flush properly for fitting/ assembly.
1] The brass nut might have a split lengthwise and a screw to close the diameter. Do not use it first. 
2] Screw have might bearings at each end. At handle end a ball bearing in a housing, and a thrust arrangement. Minimize screw endplay [thrust] with the 2 jam nuts; not snug - .001 to .0015. Now run full length of screw feeling for tight spots, very common at extent of range, and looser at first 1/3 of travel. Because parts reduce diameter from outside - unless lathe was boring more than turning. Sketch or note references where binding occurs. 

I prefer the screw/ nut combination is now out of the way, to work on slide. Use a paint marker, fingernail polish, to reveal adjustments made; simplifies returning it as close to test phase.

3] Oil slide and bed it runs on. Put the slide on carriage. Likely the gib has a notch for a screw head, or is pushed by a screw at each end. Oil gib and slip into place; the taper controls the side play only. Work the screws a little at a time to find best sliding action. When you are closing on the ideal fit, screw adjustments become VERY small. Lets say the screws are 16 threads per inch, one rotation = .062 travel, half turn = .032, quarter turn = .015. Consider one turn is 360°, half is 180° and so on, a few [even one] degrees attain movement. There, figuratively speaking, is just one setting that allows full travel and no side play. Again, oil is important part of this equation and process; there are not less than 4 paired surfaces in contact. They'll account for ~ .002-.004 [total] of oil on their own.

Let us know how you've progressed. No pressure; only 16,802 readers here at HMT.net.

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## Toolmaker51

> What material scraper is, how to replace



First off this machine hasn't issues of many, many I've run across. 
So #1. it's not Chineseium. 
#2. it probably doesn't have plastic gears. 
#3. It does have separate feed and threading shafts. 
#4. The chip pan is sure to catch coolant. I had to run [gag] a Chineseium while back and the gutters not only leaked, didn't even project beyond certain edges to stop plain drips. I'm not elitist or machine snob, but who hasn't watched rain on surfaces???
I will point out avatar to left. It's ~60 years old, 9800 pounds and I've swung 20" missile rings. My second capital purchase, I probably investigated 100 lathes with capabilities desired; sifting about a dozen when this came to auction. Shot to A list immediately.

Your SN20 carriage bridges a pair of ways; front and back and across side to side, a great surface area increase. The gap shown by your straight edge may or may not have significance. It'll be common up adjacent to headstock; if that gap is at far right side that's serious wear. I'll bet that's not the case. And definitely not beyond repair. At this instant though, it's not within scope of a couple forum posts.

Scrapers have been made in a variety of material. These can be made of solid brass, felt, shim stock, oilproof rubber, engineered plastics...or a combination. The best scrapers are composite, ie felt oilers and metal covers to protect felt and displace build up of chips. Whole idea is eliminating their access into sliding surface. 100% is nice, but hard to achieve.

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## TexBuxer

I made folder to google pics, I have problems with postimage.org https://photos.app.goo.gl/HEhxoY152FhQqShB9
Wormgear has made room for itself in casting. 
I found what is wrong in feed lever, guide piece was worn, I welded and grinded to original shape.

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Frank S (Dec 16, 2018),

Toolmaker51 (Dec 16, 2018)

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## Toolmaker51

Well, it's not cut and dry easy; just worthwhile. It's a stout machine, visible in proportions of headstock. TOS isn't common here, I've run their mills and they are astounding. 
You are learning [and doing] things millions have no clue exist. It's OK with thousands of us looking over your shoulder.

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## TexBuxer

I've been thinkin that I make diy grinder for bedways. There would be rigid frame that rolls over bearings in unworn grooves, and takes guidance from outside and underside surfaces. Frame would be 300-400 mm long, both ends on bearings. Side and under bearings slightly loaded so frame has no freeplay. Adjustable stand that carries small bench grinder with cup wheel. Stand can be mounted in each end of frame so bedways can be grinded fully. Also there could be stand for mm dial clock to monitor how much material is removed.

Ive been looking for pictures from ready devices but I could find. Some youtube videos has those. If you have suggestions, please tell.

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## Frank S

I for one am not in favor of grinding the bedways let alone trying to build some portable grinding device capable of maintaining all of the many flat angled and vertical surfaces in true precision parallelism and angularity. Before such a method is even considered other options should be investigated.
In all cases you will need a couple pairs of matched V blocks, 123 blocks long precision machinist straight edges and shorted ones , a set of parallels dial indicators depth gacues and other precision measuring equipment like a precision machinist protractor machinist squares verniers or digital calipers all of these are required to determine which surfaces are the ones worn most of all a good pencil and note pad and some marking agent such as dykem (Prussian blue).
You may find that using such devices as block sanding/ or scraping planes or a large machinist file, hand scrapers and or power scrapers will be the better choice for truing your ways. You may also find that just a good cleaning and oiling then adjusting the carriage will be good enough even if there is some slight deviation in tightness throught eh length of the travel you will need to check the concentric alignment of the spindle to the tail stock and run out.
But to try and DIY some form of grinder to do this for a 1 off would be quite an undertaking in itself. Even if the bedways were ground to shape the likehood that they will require scraping afterwards is high on the scale 
That's just my opinion

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## Toolmaker51

I agree with Frank S. Feeler gauges alone do not prove a lathe carriage cannot maintain a cylinder over available transit of ways.

The depth of tooling to just build a 100% accurate way grinder is steep. That said, portable way grinding isn't unheard of. The first issue is if SN20 ways are hardened. If so, that further complicates getting a proper sliding finish. That texture is called 'lay marks'. Like scraping, even though small, retain lubricant. A cup wheel has the wrong contact orientation. I'd question bench grinders have suitable concentricity of bearings and wheel mounting to generate flatness. Another issue of grinding in place is getting all of the length in plane head stock to tail of bed. There are not less than two measures of this flatness, not just end to end plane, but peaks demonstrated by a profilometer.
Most of the challenge hangs on attaining a guiding footprint on dependable surfaces that will re-establish continuity to worn areas. If I was there 'selling' to you, my task be illustrating carriage falls into a pair of depressed areas simultaneously. 
Lets say you are set on restoring the ways. Remove the carriage, rent a full length cast iron straight edge [or optics] determining how far out it really is. A simple google search will locate machinery rebuilders that will estimate or quote cost to accomplish what is needed.
That will either dissuade or initiate building a DIY way grinding machine.

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## TexBuxer

I have minimal budjet in this project. My car is very greedy  :Smile:  I know what it will cost if repair is done by professional, I could get decent lathe with that money. I paid this lathe with work, and I like to diy my stuff. Lathe is only supporting tool for my car projects.

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Toolmaker51 (Dec 23, 2018)

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## Frank S

> I have minimal budjet in this project.I know what it will cost if repair is done by professional, I could get decent lathe with that money. I like to diy my stuff. Lathe is only supporting tool for my car projects.



All's more the reason to shy away from an attempt to build a grinder set up.

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Toolmaker51 (Dec 23, 2018)

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## TexBuxer

Bedways are now grinded with homemade grinder. Now I have to rise saddle to correct wear, I was thinking to get suitable metal rulers and tackweld them in to saddle bottom to rise it. Hope there isn't too much friction. Scrapers must be fixed too.

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## Frank S

How were you able to maintain flatness, parallel square straight and true to all surfaces using a grinder set up running on the ways themselves?
And why would you need to raise the saddle? if you took so much off that the rack and pinion no longer have proper mesh then shim the rack down to meet the pinion.
the Head stock and the tail stock alignment are the 2 most critical items. I can't see the height of the saddle being that critical unless you too lots of material off of the ways

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## TexBuxer

I had to grind so much that lead screw is not in correct line. Frame of the grinder is longer than saddle and it slides in surfaces that doesn't wear, I made frame so rigid that it won't vibrate and took small amount at a time. There is more pictures in shared gallery. https://photos.app.goo.gl/HEhxoY152FhQqShB9

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