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Thread: Zyto - Tyzack lathe refurbishment

  1. #1
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    Zyto - Tyzack lathe refurbishment

    I bought three of these Zyto lathes in quick succession late summer 2013.
    One was for the most part complete and in serviceable condition. The other two were some what incomplete and rather in need of attention, but complimented each other in terms of missing / damaged / worn parts.
    After a deal of vacillation, I decided to build one good machine from the two donors with a view to keeping that one and follow through with a refurbishment of the serviceable machine with a view to selling it on when complete. The third machine which will be very short of original parts that would make it useful as an operational Zyto lathe has not had its future determined yet. Depends on what it is like under all the surface rust and grime etc.
    Unfortunately I did not photographically record the first rebuild of one out of two donors. That was completed late Autumn 2013. It went well, if being a deal more work than I had bargained on, mostly due to the fact as I learned during the process, that these machines were essentially hand built and what you may expect to be standard parts were in fact not. There appears to have been quite a bit of selective assembly and specific fitting to make the components a working and viable machine tool.

    So what follows will be the breakdown and refurbishment of the mostly serviceable machine and the clean up and inspection of the remains of the very incomplete donor. If the donor bed checks out OK I might just CNC it. I have most of the gear necessary for that. See how it goes?

    So to start with....
    Some background on a Tyzack Zyto lathe.

    http://www.lathes.co.uk/zyto/index.html

    And a couple of pics of the mostly finished (are they ever really finished) machine doing something

    100_1646small.jpgR-ada2.jpgR-ada3.jpg


    And a couple of pics of the machine(s) to be refurbished


    100_1648small.jpg100_1649small.jpg

    It might be a week or two before I engage with doing something with them.

  2. #2
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    I dragged the donor frame out today, took off the headstock, rubbed the surface rust of the bed with a bit of steel wool, and dusted over the obvious high spots and dinks with a shard of FF India stone.

    Here are a few pics of various aspects depicting the general shape and construction. May be of interest to the "AA lathe design team"


    100_1709small.jpg100_1710small.jpg100_1711small.jpg100_1712small.jpg100_1713small.jpg100_1714small.jpg100_1715small.jpg100_1716small.jpg

    Here is a couple after a clean up


    100_1717small.jpg100_1718small.jpg
    100_1719small.jpg100_1720small.jpg

    Came up better than expected. There are quite a few minor dinks and some superficial rust pitting, but on the whole fairly good. Not pretty, but the straight edge and "Rizla paper" test suggested it is reasonable flat and true to less than 0.002".
    The acoustic test (tap with a copper mallet) gave a reassuring ring tone, so no major cracks. the original machining is clean and visible on the flanks of the bed, which is good. I rather suspect the top of the bed has been attacked by someone with a bit of sandpaper at some point in the past... No apparent real damage though
    So it looks like it has a useful future.
    It's gone for a rest in the shed for a few days until I have time to tinker with it again.

    If there any specific pics of the construction wanted, then best ask.

    Couple of quick stats
    Nominal section is about 3/8" for the most part except where it obviously is not.
    Weighs in at about 25lb according to my bathroom scales.

  3. #3
    Excellent Mr Greg! So that bed is only 25 pounds and yet it looks very robust. Were these lathes rigid?

    If a 25 pound casting can do all of that, I believe the Gen Gen II could have a much heavier bed. Say 50 pounds finished? That is easily poured once you add machining tolerances, gates, spruing and feeders.

    Thanks for the info and please keep the pictures coming!

    Regards,

    Justin

  4. #4
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    So that bed is only 25 pounds and yet it looks very robust. Were these lathes rigid?
    Well, now you're asking

    At a push, the lathe is capable of about a 0.050" depth of cut, with a good sharp tool in free machining mild steel. I wouldn't normally do a roughing cut of more than 0.025"
    I don't think the bed/frame is the limiting factor, if that answers it for you.
    I will try to cover some of the strengths and shortcomings in due time

  5. #5
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    Had a spare half hr so did a preliminary blue out of the bed vs saddle and saddle vs bed.
    The purpose being to verify what I saw with the straight edge and generally get a better feel for the state of them.
    First, blue up the saddle and see how it engages with the bed.


    100_1721small.jpg100_1722small.jpg100_1723small.jpg

    More or less what I was expecting, the bed did seem a little low toward the center with the straight edge. The flanks of the bed seem to be engaging well with the saddle.
    I am not too concerned with the fact that I am only seeing mating toward the edges if the bed. If I was seeing contact mostly toward the center then the saddle would be inclined to rock some, which is not good.
    So. Not perfect , but still looking good

    Next, blue up the bed and take a look at the saddle contact areas



    100_1724small.jpg100_1725small.jpg100_1726small.jpg100_1727small.jpg

    The inside faces that engage with the top of the bed seem fairly flat and parallel, so no obvious sign of twist / warp. (might still be bent on axis with the bed) The fixed side face is showing good contact at both ends of the saddle with minimal contact toward the centre, which is good.

    There is apparent evidence of some wear on the bed toward the centre of the bed where the saddle would normally engage. The fact that the blue is showing mostly contact toward the edges may suggest that the saddle is not original to that lathe. It was just a heap of partially assemble bits when I bought it so I have an open mind on this.
    The saddle gib strip is missing, so until I get the time and material to make a new one, I won't be doing much more with the bed / saddle checks.

  6. #6
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    It's not so much wear I am checking for as general neglect / abuse and manufacturing defects.



    Had a rummage through my stuff and much to my joy I found this. Quite forgot I had it !

    100_1728small.jpg

    It is an unopened package of 3/16" gauge plate, with a date stamp 12 May 1977. I prob acquired it sometime late '70s and squirreled it away. It has waited a good time for a purpose.
    Well now it has one, a gib strip.

    Pic of spotting through of adjuster screw pockets.


    100_1730small.jpg


    With a gib strip in place I can now do a little further assessment of the state of things.
    Next step was to determine if the bed was reasonably parallel. This simply done by adjusting up the screws and feeling the saddle up and down the length of the bed for tight or loose spots.
    Again not too bad, a little loose here and a little snug there. Mostly felt OK around the headstock end.

    Repeated the process with some blue. As before fairly generous, as this is still preliminary.


    100_1731small.jpg100_1732small.jpg100_1733small.jpg


    The area near the headstock end with more blue is the snuggy feeling bit. The lightly blued area near the tail end is a little more on the loose side.

    Lastly a further quick and dirty blue out using a mini surface plate over the top of the bed.

    100_1737small.jpg

    So generally looks like it is all agreeing and worth spending a little more time on.

    Closer inspection of the saddle showed that the original machining was a little on the crap side. the mating faces that engage with the top of the bed are a little proud at the edges. This would account for the blue trace at the edges of the bed.
    I put thisfault down to the dovetail cutter being on the blunt side at the edges and thus leaving more material on than should be. This is a bit of an arse, as it is difficult to get to flatten out what with it being right inside the angle.
    The "beady" eyed observers will also have noticed that the gib locking screws aren't not exactly neat and orderly either.
    Anyways, with a little stock removal here and there, it can be made better.

    So much for doing things like they did in the "Good old days! "

  7. #7
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    Yes, dovetails are interesting.
    Usually at 60deg they are a truncated equilateral triangle. Anything you do to one face affects the plane and dimensions of the other two faces.
    More work up front, but are, for the most part, self guiding in two planes under load.

    Spent a bit of time relieving the outer (inner ) edges of the saddle to correct the excess material problem and also relieved the gib a bit where the screws apply pressure. not much , just a couple of 10ths with a stone & needle file.
    Using a lot less blue now.


    100_1740small.jpg

    Note the blue patten off the surface plate, just spots.

    Now the same again, but bluing off the flank of the dovetail bed.

    100_1742small.jpg


    Now a couple of pics of the saddle with the relieved edges and some flattening - fitting wrt to the top of the bed.

    100_1746small.jpg100_1747small.jpg

    Ref pic of the bed blued prior to getting a blue trace on the saddle. Now working with a thin coat of blue.


    100_1748small.jpg


    This was quite an iterative process of blue up the bed and take some material off the saddle, then blue up the saddle and take some material off the bed. Material off in small measures with needle files and stones.

    Now the top of the bed and mating face of the saddle are in a more respectable state, I will turn attention back to the flanks

  8. #8
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    A few more pics of the of the process.
    A bit of work on the flanks of the bed to flatten out some of the high & tight spots, then a bit more off the top with a large india flat stone.



    100_1749small.jpg100_1750small.jpg100_1751small.jpg

    Another rizla paper test on one of the lower spots. Initially this spot was indicating clearance of one paper, but nipping on two, so circa 0.0015". Now firmly nipping one paper so less than 0.001"

    100_1752small.jpg


    A couple more of the top getting better.

    100_1753small.jpg100_1755.jpg

    The final blue outs.

    100_1757small.jpg100_1756small.jpg100_1758small.jpg


    I did do a little more with the saddle here and there, also took a little material from the centre of the guide side inner flank, as most of the wear will occur at the sides.

    That's pretty much where I'll leave it. I have good contact area on the whole, and the low spots are likely within a couple of 10ths. The saddle is slightly snuggy toward the headstock end and in the mostly used working section a couple of inches past where the chuck will be holding something.

    A couple of pics of the bed & saddle cleaned up. this gives an idea of how much material has been removed form the point where I started.

    100_1764small.jpg100_1765small.jpg100_1767small.jpg100_1768small.jpg100_1769small.jpg

    Lastly a little critique

    100_1766small.jpg

    The dovetail bed and frame are fairly robust and proportionate. Probably one of the best features (IMOH) if this little lathe.

    The saddle could do with (IMHO) a little more meat around the flanks. Especially on the gib side, which takes all the horizontal cutting force. I'm sure it would help, and would not have caused other problems.

    Having said that it does do well and works OK for what it is. A small model makers lathe.

    I'll probably tackle the Tailstock next while I ponder what to do with it. It is rather incomplete
    Last edited by MrGreg; 04-30-2014 at 09:59 PM. Reason: typos

  9. #9
    Same here, I like to see the working lathe parts and all the fitting pieces. It's interesting that you are using a flat stone it really leaves a nice finish, good luck.

  10. #10
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    As per my Orig post, I will be moving on to the almost complete lathe after a little further work on what is left of this donor machine. I have the tailstock to do, repair a leadscrew with the end broken and the headstock and spindle assembly. I will leave the headstock assembly until last as I have various options on how it will be driven and am a little undecided on which? I have no further parts of this one, so it may take on a new non std life. TBD

    The mostly complete one is in excellent working condition apart from the main spindle has excessive play and the leadscrew half nuts are missing. ( or rather I only have one ). There is very little wear & tear. So all its working parts can be seen during the strip down and re assembly.
    BTW The mostly complete one will be up for sale when finished.

    Re the fitting & bluing thing. The tricky part is not getting blue all over everything you touch, including the wife, cat etc
    It's very pervasive stuff!

    Perhaps more of a discipline than an art. As you say, not to be hurried. And yes you have to be clear from the start what the end game is. Easy to loose sight of what you are doing and chase your tail.
    It is not an easy process to describe either.
    I usually use a tooth brush to apply it, Would generally be looking to put a film down (in this instance) which will have a thickness of 0.0001" to 0.001" using a scrubbing action (as if you were trying to clean something) without any blobs. So the film needs to be even and translucent. IE you can see the metal through the blue film. Obviously the contact points will take the blue. Perhaps less obviously the blue may be smeared (almost) completely away where full contact has been made and the wiping action has removed it. This can be seen to some extent in the previous pics.

    Best to try it out and experiment really. A mini surface plate can be made from an offcut of Thick glass (shop front?) 3/8 - 1/2" thick by, say 6 x 6" ish not much more, glass is bendier than you might think
    It will prob be flat to circa 0.0001"

    Rizla is a brand of hand rolling tobacco cigarette paper. Their quality control is excellent. The paper is (Green type) a consistent 0.0012" thick (Blue type 0.001"). For a guide measurement and nip test it is ideal. It has a unique blend of strength and fragility such that it will tear if you pull it too hard when nipped. This makes it a much more sensitive test than a feeler gauge. Feeler gauges can easily act as wedges and are somewhat unforgiving.


    Nope! Not used a planer blade for either purpose. I would want to check it first for flat/straightness rather than assume. An old file can find a new life as a scraper.

    As mentioned, you may find that blue gets applied to many types of machines and engines all by itself.
    Last edited by MrGreg; 05-03-2014 at 04:10 PM. Reason: Error + additional info

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