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  1. #46
    Join Date
    Jan 2016
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    Gosford
    Age
    57
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    91

    Default

    I wont take the camera around to the other benches then, lest you change your opinion of me.

  2. #47
    Join Date
    Oct 2001
    Location
    ACT
    Posts
    512

    Default

    looks like you have enough change gears to do most threads. I think it was meant to have two 20t gears in a full set but the thread charts I see online dont seem to need it? may even be able to use Myford gears.
    So a 21t (may need two) would probably let you cut metric threads.

  3. #48
    Join Date
    Jan 2016
    Location
    Gosford
    Age
    57
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    Default

    The spindle gear is a fixed 20 and I have 1 each of 20 to 65 in 5 increments. A 21 apparently makes metric exact possible but my early calculations say that it is possible to do low tolerance metric with what I have.
    Instead of 1.5 mm pitch I can get 1.501 mm. I'd be happy if the machine can do that.

  4. #49
    Join Date
    Jan 2016
    Location
    Gosford
    Age
    57
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    91

    Default

    Heavy gal lathe tray folded up using bush metalwork techniques. A hammer and a piece of RSJ.
    Folded edges to prevent more loss of blood. I used a bit as paint primer on it already.
    Steel bar lathe lift spacers roughed in.
    Attached Images Attached Images

  5. #50
    Join Date
    Jan 2016
    Location
    Gosford
    Age
    57
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    91

    Default

    I have a few photos to post later. The lathe tray is done and I was inspired by a youtuber's method of attaching a dial Indicator to the cross slide so I built one today.

    The question now is:
    Can a thread insert (if available) in the saddle for the cross-feed screw bring that feed back into any semblance of tolerance? With the dial indicator fitted, I have now been able to measure the cross-feed free play and I have 0.42mm or 0.0165" of slop. So that's 0.84mm or 0.033" in diameter.

    I can work with this by simply compensating with the hand wheel to take up the play in either direction, but doing this will become very tiresome on my poor old brain. It will feel like driving a boat with a loose tiller steer outboard engine. If I'm only winding in one direction it is fine but I now have to use my abuse hardened head to think about stuff that I shouldn't need to. Again, it would be really good to know how much slack there was when this was new.

    So I now need to work out if the cross-feed can be fixed and I need a new full nut for the lead screw, but at least that is a replaceable part. Mind you some of the old School lathes I have worked with were pretty ordinary too.

  6. #51
    Join Date
    Jul 2016
    Location
    Melbourne
    Age
    30
    Posts
    670

    Default

    If you have the changewheels for it just make a new cross slide and full nut, is the cross slide screw square just like the leadscrew?

  7. #52
    Join Date
    Jan 2016
    Location
    Gosford
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    57
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    Default

    Good point and good question. I've had it off but didn't really look. I think the cross feed screw is only about 3/8" diameter. If it's the threaded hole on the carriage casting that's worn though, it won't be quite so simple. That's where I thought of possibly using an insert. If it is the screw then it will be easier to fix. I'll investigate tomorrow to try to determine which part is worn.

    Also its a bit of Catch 22 there. Need good tolerance to make a good thread and need good thread to have good tolerance. I'll work something out even if it takes a few goes.

  8. #53
    Join Date
    Jul 2016
    Location
    Melbourne
    Age
    30
    Posts
    670

    Default

    If the nut is integral to the cross slide im happy to bore it out for you after you make the insert.

  9. #54
    Join Date
    Jan 2016
    Location
    Gosford
    Age
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    Default

    Thanks for that offer CW. I'll do some closer examination later today.

    Here are some more pics. As I posted earlier, I was inspired by a Youtuber's method of attaching a dial indicator and I happened to have a very odd shaped offcut of 10mm Ali plate left over from a mates anchor winch bow plate repair. Slow cuts on the Hafco bandsaw and some file work did the job. I now need to pretty it up but it is functional and I can move the cross-feed in increments of 0.005mm (or better). I took 6 photos of the dial zeroed and then 0.01mm increments but I wont post 6 photos. You get the picture.

    I had considered a scientific retort stand style assembly but went with this instead. The only drawback is that the gauge is single direction, whereas on a stand it may have been usable in different orientations.

    The tray finished and painted in Gun Metal Hammer tone over etch primer.
    Tray.jpg


    Rough shaping the dial indicator clamp body.
    Cut 1.jpg

    Test fitting to the back of the carriage.
    Fit.jpg

    Testing assembly.
    Test Top.jpgTest Side.jpg

  10. #55
    Join Date
    Jan 2016
    Location
    Gosford
    Age
    57
    Posts
    91

    Default

    More pics

    Drilled, thread tapped and attached.
    Drilled & Tapped.jpg

    Angle on.
    Angle on.jpg

    Dial indicator on. The holes are 10mm spacing to allow for 10mm limit of gauge capacity. I may turn this into a slot.
    Dial On Side.jpg

    And working.
    Zero.jpgZero +5.jpg

  11. #56
    Join Date
    Jan 2016
    Location
    Gosford
    Age
    57
    Posts
    91

    Default The wheelbarrow joke.

    Quote Originally Posted by caskwarrior View Post
    If the nut is integral to the cross slide im happy to bore it out for you after you make the insert.
    The nut is integral as you put it, being just a threaded hole through the casting. There is insufficient metal above it to even think of boring it out to either rethread in a different thread or use an insert. It is what it is. The fit of the screw in it is as loose as blazes and it literally flops around.

    However, I was able to reduce the measurable free play down to 0.25mm by simply tightening up the handwheel on the shaft to the point where it's just able to turn with minimal resistance. I can reduce it slightly more but any tighter and it is no good so there is a little slop in that connection that is unavoidable but not really significant. I could always nip it up for more precise control and loosen it again when not required.

    What I did find though, is possibly an easy fix. The screw is standard 3/8" X 16 Whitworth thread form and it is 0.008" undersize. Not much I know. I found a full diameter 3/8" Whitworth bolt and it is better fit but still a little loose as well, so it is possible that both nut and screw are worn or they were never a good fit. Possibly cutting a new screw that is the full 3/8" (or even slightly OS) is all it will require to improve it even more. Not too difficult to achieve and definitely worth a shot. I can't say if it is the parts being worn down or if that's how it was from original. Again the free play is consistent along the full length so it doesn't definitely indicate only wear and tear.

    It looks like a custom thread screw might be in order.

    Edit. I used to drive trucks part-time for my FIL's transport company and deliver wheelbarrows among other things. There was the often repeated, amusing the first time you heard it, joke about the boss who sent his apprentice to get a wheelbarrow and then questioned why he returned with two. The apprentice answered his boss with , "Did you expect me to carry it?"
    So the reason for the joke is, if I need a bigger lathe to fix my little lathe, how did they make the biggest lathe?
    I've started work on a new cross-feed screw and it's progressing well. The good news is that the dial indicator setup is working great. I'm thinking that I might put a 16 TPI Whitworth thread pattern on a 10mm diameter screw to see if it reduces the flop.
    Last edited by glivo; 6th Jul 2018 at 07:08 PM. Reason: Additional information

  12. #57
    Join Date
    Jan 2016
    Location
    Gosford
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    57
    Posts
    91

    Default Screw Dimesnions

    Addressed to BaronJ. Thanks for the suggestion. I had considered using a precision threaded bar and may still resort to that if I test a piece and it is a good fit in the existing nut. A new nut isn't an option as it is just a threaded hole through the carriage casting and I'm not interested in mucking about chopping bits out and affixing new parts. This is why I'm attempting to machine a custom part to counter the wear (or existing original loose fit) already in place. Using threaded bar would involve the attachment of a small 1/8" thick retaining collar, probably by brazing, and it would also mean that the shaft that goes into the handwheel would be threaded instead of solid cylindrical. With good steel, this would probably be OK. I'll post a rough drawing of the required part after dinner.

    As far as the part I'm making now goes, exactly 10mm diameter with 16 TPI is too big. The 3/8" diameter (under by 0.008") of the original part is too loose. So the solution is in between. It's now a matter of little by little, cutting and test fitting. I'll just ever so gradually reduce the diameter, recalibrate and chase the thread. Pain but necessary.

    Here is a crude whiteboard drawing of the part I need. It could be fabricated and it certainly could be made very easily on a lathe with better facility than the one requiring the replacement part. A bit like driving to the tyre guy on flats.
    CF screw.jpg

    Here's what I have at this point. Dia 10mm with 16 TPI is too big. The shaft that fits into the handwheel is held in the chuck. I need to reduce it bit by bit and re-chase the thread until it is a good fit. I have no idea of the finished size required to match the nut (threaded hole) other than the fact that it lies somewhere in between the original part and what I have here.
    CF Screw 2.jpg

    Looking at that photo blown up, I'm seeing what my eyes didn't. I think the lead screw and nut might well be worn unevenly and giving me variation in the cut thread over the length. Might be wasting my time trying to drive on flats. The photo is out of focus and the cut finish is terrible but it looks to me like I still have flat top threads at the tailstock and V apex at the headstock. I'll magnifying glass inspect tomorrow.
    Last edited by glivo; 7th Jul 2018 at 08:21 PM. Reason: Drawing

  13. #58
    Join Date
    Sep 2012
    Location
    North Yorkshire UK
    Posts
    2,001

    Post Drunken thread...

    Hi Glivo,

    Looking closely at your photograph, it looks like the thread is not just badly worn but drunken to boot !
    That being the case I would seriously look at the nut part with a view to boring it out and making an insert threaded to suit a new screw. I would see this as an opportunity to fit a nicely calibrated dial in either metric or imperial. M10 X 1.0 might be good.
    Best Regards:
    BaronJ.

  14. #59
    Join Date
    Jan 2016
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    Gosford
    Age
    57
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    Default

    The photo is of the screw I've been roughing in, while still using the original one that looks a lot better but is very loose. The one in the photo is turned out of hot-rolled, who knows what, steel and it is still too big. I was planning to reduce it's diameter slowly in stages today, re-chase the thread each time, and see if I can get a good fit in the nut. As I say though, now after looking at the photo myself, I may abandon it. I'll have a closer magnified look at it today but I doubt I can produce an even thread, of the standard required, on this lathe if the lead screw and full nut are not providing smooth and regular progression of the carriage.

    I originally measured the free play in the lead screw as being of constant magnitude along the full length, but yesterday I found that the last 1 1/2" or so at the headstock end was noticeably tighter to turn the handwheel to move the carriage by hand. Common sense tells me that if the wear along the length of the lead screw is even, then it is possible to still produce an even thread. However, if the wear is uneven, then any thread produced from it will have the same defect transferred and I think that's what I'm seeing in the photo that my eyes, with spectacles, didn't see. Anyway, I'll put some magnification on it today and have a close up look and measure.

    I think it is a bit of a stretch to try to replace worn lathe parts on the same lathe that has worn parts. As anybody would expect, any error caused by the worn parts would replicate onto the new parts. I may need to investigate the threaded bar option. Replacing the nut is not going to be an easy task as there simply isn't any bulk of metal around it.

    Incidentally, there is another "Advance" lathe in "restoration" condition on Gumtree, listed yesterday in Meningie SA. It is another old one but the model with the half nut and reverse tumble gear. I paid a fair bit less than half of what he's asking for it ($650) and after my little punt on the day I bought mine, I came out of the day only $50 out of pocket, so in my mind that's what I paid for it.

  15. #60
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    Jan 2016
    Location
    Gosford
    Age
    57
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    91

    Default

    Update:
    The options for the cross-feed screw are narrowing and not looking great. I can't buy Whitworth threaded bar, only UNC, but 3/8" X 16 UNC High Tensile threaded rod is again under the 3/8" nominal diameter by a fair amount and along with the 60 degree thread form, instead of 55 degree, it is a very sloppy fit in the nut (threaded hole). It should be a tighter fit as it has a bigger minor diameter of 8mm instead of 7.9mm on the internal thread, but it's actually worse because the major diameter is undersized. It's worse than the existing screw so I'll be returning it for a refund. I've found a short length of Whitworth rod online that can be imported from the UK, but really it is a leap of faith that it would fix the problem anyway. There may be somewhere to buy Whitworth in Oz but everybody just stares blankly at me when I even mention it. Even though I explained the need for close tolerance fit they still think a different thread form will work anyhow. Clearly it doesn't.

    I did find that I have some 3/8" X 16 thread repair inserts left over from when I had to repair a bandsaw a few years back but it is not possible to use one anyway. There simply isn't enough metal on the carriage to allow drilling out and screwing the insert in. If it were attempted and didn't work the lathe is 100% useless.

    There are 3 conclusions which could be drawn from this. Either there is wear in the nut or it never fitted properly in the first place. This lathe by all other accounts does not appear to have seen much work so I'm leaning more to the latter. The third option is a bit of both.

    Either way, the only solution I can see to fix this is to produce a bastard screw by repeated trial and error until one is produced that gives the correct fit.

    The lead screw on the other hand is repairable but not by me, here at home. I would either need to have a new full nut made to match the existing screw (if possible and the screw isn't worn) or just replace both with a newly made matching set, which is probably the best option. Do I want to? Possibly not. It may be that the machine is just not up to any really fine work. Maybe it never was.

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