Ultimate Manual Lathe - threading - Page 2
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  1. #21
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    There is also the additional thread chasing attachment as fitted to Hardinge and other notable lathes signifying serious threading intention.




    For an idea of scale: The carriage hand wheel is six inch in diameter and the bed is about fourteen inches high.

  2. #22
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    Trevor, dont forget that I have an A20 right near you in Cherry Grove.
    traversing yhe carriage, spins the ball nut on the ball screw.
    The master screw interlocking clutch within the apron is made with a single tooth clutch.

  3. #23
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    Becuase the HLV-Hs half nut is never disengaged when cutting threads the spindle doesn't care what the thread pitch being cut is. When the carraige hits the stop or the operator kicks it out himself the leadscrew stops turning while the spindle keeps running pull the quick retract lever and throw the leadscre engagement lever into reverse and the leadscrew reverses to bring the tool out for another pass. It works on any pitch in the gear box or any of the possible pitch's with the change gears. I fully intend to build something similiar into my bench lathe when I get the chance. Sometimes there is an advantage to not having a QCGB for threading and feeds. The other side of the coin to the HLV-Hs leadscrew drive is its variable speed feed motor for cross and longitudinal feeds. The drawing below shows one way to do it. The pale green shaft and gear is the input from the gearing, it turns the first layshaft which truns the second layshaft which drives the reverse leadscrew gear. The dog clutch in red has slides on the leadscrew and drives it through a key (a slpine would work too). The leadscrew reversing gear runs on a bushing so that it can run in the opposite direction as the leadscrew when threading towards the headstock. The dog cluth and gears have clutchs cut in them that can engage at only one point. The dog clutch would be conected to a hand operating lever for shifting purposes and also linked into a stop rod to allow automatic drop out of the leadscrew when threading to a shoulder and relief groove.

    http://img.photobucket.com/albums/v1...ingSystem5.jpg

    [ 10-29-2007, 11:40 PM: Message edited by: Spin Doctor ]

  4. #24
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    Spin, you need to reduce that image or change it to a link..way too large...causes folks with lower resolution settings to have to scroll horizontally just to read every post in this thread.

    Doug N., those semi auto chaser threaders are quite a PITA to set up and only useful for either production situations, or home shop "I'm desperate and I happen to have the right lead and chaser lying aroun" situations. Which, with CNC means they are not useful at all anymore for production and a bit silly for home/small shop use.

  5. #25
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    A disadvantage to the HLVH is that you can't thread with the spindle running in reverse(as is internal threads running the tool out of the bore). The manual states not to do it so I assume it has something to do with the stops.

  6. #26
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    The Monarch EE uses the DC spindle motor dynamic braking to safely thread leaving the half nuts locked in.
    Works very well if a problem does not develop in the drive.
    Its well known the Hardinge cuts nice threads. In the Monarch manual it states, for extreme precision threads, the half nuts are left engaged.
    What can happen engaging the half nuts is an error can occur where the nuts may not exactly settle in the same each time.
    This problem shows up most often on a finish pass, when the tool takes an unexpected heavy cut messing up your threads. The carriage can be a little ahead or behind from the camming in of the half nuts. That is, if the nuts are left engaged, they settle in. Thats how the Hardinge cuts nice threads every time.

  7. #27
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    One reason for a manual Lathe with 2 leadscrews vs CNC, NO ELECTRONICS/Software/Steppers/Servos to be obsolete in 10~15 years..

    I have thought it strange that 2 leadscrew machines are so rare...

    Simple to keep seperate half nuts from both being engaged by only having 1 handle that pops off one half nut engage shaft, and pops on other ( with a tail piece on handle that ensures other shaft is in open position)

    This simple setup should not add too much extra cost, and would be the most flexable system with 2
    thread dials. Not an elegant solution, but a Practical Machinist one [img]smile.gif[/img]

  8. #28
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    Doug931,

    One of these days, we're gonna have to meet!

    Did you snatch the Ikegai that was on Crown Asssets a couple years back?

    That was the one that came from our shop (the one on CA, that is).
    I never saw it pass through, but I was busy with a couple other things at the time.

    I know we handed a pile of stuff off to the CA people, to be included with the lathe, but I have no idea if the stuff made it to the end purchaser. Books, and gears mostly, like all the spares, in the storage box.

    Hey, are you the Brit bike guy?

    Cheers
    Trevor Jones

  9. #29
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    Trevor, nope I didnt get the one on base. I bid on it, looked at it, didnt get it. It was bare bones, no acessories, no books. I suspect it was an inside deal with whoever got it already had the spares.
    the one I have came from New York state with most of the acessories. I bought the manuals over the!
    web.
    Yep, I am the Brit bike guy.

    it would be nice if you could come over and see my shop. I need some advice on repairing the tail stock on the A20.
    Doug Jones 594-2295

  10. #30
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    Spin, your diagram shows a single tooth dog clutch, same as on the Hardinge, or Monarch, as well as many L&S, American, Hendey, LeBlond, and other lathes of this design. This is usualy referred to as a toolroom lathe. Any of these lathes can cut threads with no dial, as long as they have reverse to leadscrew and a single tooth dog clutch. All the above mentioned lathes also have stops to kick out the leadscrew in both directions, and the L&S models had a ball micrometer stop which allows three turns of retract, inside or outside, and then return to a dead stop. Depth of cut is set with the compound and the result is nearly effortless threading. These features went up to and over 24" swing on some models.

    As Matt says, I really doubt you can use the clutch on a metric thread if you have an imperial leadscrew. Although the relationship of the spindle to the leadscrew remains constant, the effect is the same as closing the halfnuts on the same mark every time. That's still not going to work with a metric thread on an imperial leadscrew. You'll have to leave the half nuts engaged and reverse the spindle, which is super easy and super fast, but the same way I have to cut them on my crappy Jet. Some of the big old lathes had a reverse in the clutch, which would accomplish the same thing without reversing the motor.

  11. #31
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    On the HLVH, the lever which operates the dog clutch reverses the leadscrew, not the spindle. It works fine on metric, and doesn't even have a thread dial. Been that way since about 1917. Same with the retractable compound. On the 10EE, I think you have to have the ELSR option to do this (not sure though). Unlike the electronic CNC threading(which is probably the "ultimate"since it can do any pitch without gears), this will still probably be working in another 80 years.

    regards,

    Jon P.

  12. #32
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    Don, I dropped the image link and substituted a a link that doesn't import the picture directly. Those overly large pictures in threads annoy me too.

  13. #33
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    Milacron, Yes chaser threaders are a right royal PITA and the sign on a used machine that the carriage “may” have spent its life repeatedly on the same area of bed.

    It is interesting that Hardinge, Schaublin, and Holbrook among others, were exponents of such devices. It is worthy of note, that said manufacturers were also exponents of lever withdrawal mechanisms on the compound slide, for improved conventional threading.

    These manufacturers were at the forefront of design, all offering lathes with infinitely variable speed, independent motor driven sliding and surfacing. In the case of Holbrook, the motor was mounted inconspicuously in the headstock end of the bed. (Good design! Bad marketing move, if you’ve got it flaunt it, especially at machine tool exhibitions)

    The Schaublin 135, 160 threading anomaly is interesting, the Holbrook Minor also has a thread range anomaly, only 30 threads with the standard box, before resorting to change-wheels. The Hardinge has the gear-case size problem, (at least in the UK when we went metric). All problems corrected on later models or with larger existing models in the range in the case of Holbrook.
    An interesting and hitherto unmentioned irregularity, is the British Association thread, AKA “BA”, it is metric. With Swiss origins, I believe.

    Could it be, that for part of the market sector these machines were aimed at during the design phase, it was envisaged that chaser threaders would be preferred? Indeed they were already in use on earlier products from the same manufacturers? The range of specialist threads per market sector is small, and easily accommodated by the chaser. A metric lathe cutting an inch thread using a chaser is very plausible, considering lathes without even a leadscrew were using a chaser to cut threads.

    Obviously, what is thought at the design stage, and what is wanted in the real, fast changing world is usually slightly different.

    Apologies to 10EE aficionados, I was trying to work out if by inclusion of electric feeds at the conception phase, the designers eye was taken off the thread range issue. The possibility also exists, that in not wanting to lose market share in industrial sectors with an existing chaser user base, manufacturers also neglected the “extended range” threading issue.

  14. #34
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    point taken on semi-auto chasers. And of course in a real production situation cnc is the way to go for threading. But manual chasers are a bit more than just "silly" for small shop use especially where specialist items are made. I can't justify cnc for the items I make. But certainly prefer hardinge manual chase threading for making multiples of small-ish screws over cutting them on an engine lathe.

    They are a (formerly) "fast" method of screw & thread production whose day has passed, but the application lives on usefully in some niches.

    smt

  15. #35
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    But manual chasers are a bit more than just "silly" for small shop use especially where specialist items are made
    C'on ST, just accept them as silly and be embarassed all the way to the bank

  16. #36
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    I have a Pratt & Whitney Model B with the single tooth dog clutch, which according to the manual should not be used at top speed (which is a leisurely 540rpm)

    It works the same as SpinDoctor's solid model, and looking at it, I cannot see how you could operate it at Hardinge speeds, unless it had some sort of synchromesh. Does anyone know how they get it to survive? Admittedly the saddle and leadscrew on my machine weighs a lot more than a Hardinge's, but even so ...

    In my case, it's one of the things I'm going to have to rebuild, because the single tooth clutch is ****ed.

    I guess the lathe operator down at McMurdo base, where this machine spent the 50 years prior to my purchase, didn't have somewhere warm to curl up with the manual !

  17. #37
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    My ideal lathe (failing the digital threading - I'd be all over that if I had the $$$ and wasn't jinxed where fancy electronics are concerned) would have NO QC box, instead I'd go for a Martin Cleeve-style banjo with a single clamp lever and well thought out quick-set gears.

    I entirely agree with a previous poster that QC boxes can be limiting, particularly if you're cutting really strange pitches, either of the other 'language' from the leadscrew, or things like wormgear worms and hobs which can only ever be approximated. It also means you can't work dodges like correcting for slight pitch errors in your leadscrew, say for turning up a micrometer-style adjuster for a critical application.

    As MC pointed out, "locking up" a certain number of gear wheels in a QC box, as opposed to the flexibility of being able to arrange them on a banjo, (shades of "Deliverance !") drastically reduces the available ratios.

    A separate variable speed feed arrangement along Hardinge lines would complement this so compound gear trains were seldom required. When the majority of pitches are covered by simple gear trains, changewheel gearboxes are pretty quick and easy to change over.

    (If I was really gilding the lily I'd follow abarnsley's lead and opt for two leadscrews, which would keep the geartrains ultra simple)

    I'm in the process of setting up my small lathe along these lines, albeit with only one leadscrew. To toggle between screwcutting and feed, the banjo will swing at will from the tumbler cluster across to a gear keyed to the output of a geared DC motor, driven in proportion to the larger DC motor driving the spindle. The different simple trains which happen to be set up on the banjo, along with the need for different feeds per rev, will be accomodated by varying the voltage ratio between main and feed motors.

    Do Hardinge feeds automatically vary as the spindle speed is changed?

    Ideally I'd make a single tooth clutch (which Martin Cleeve also did, and details in his thought-provoking (posthumous ?) book "Screwcutting in the Lathe"), but I think having one of these in the family is quite enough (see post above)

  18. #38
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    The Holbrook Minor has the option of a stop rod system, operating micro-switches. In essence the carriage runs between two stops cutting the thread. The carriage trips a stop, the machine stops and the operator withdraws the tool and allows the carriage to traverse back to the start position, and automatically stop. The procedure is repeated until the full depth of thread is attained.

    The system will operate on external or internal, threads, right or left hand threads, Inch or metric threads without disengaging the half-nuts. The manual does warn about not using “excessive speeds”, but as the machine is capable of 4,000 RPM I suppose that is fair enough.

    The machine is actually designed with all its motive elements in the base; a 2 inch Poly-V drives the spindle.

    Unfortunately the Holbrook Minor is a rare machine, and the stop rod system was presumably an expensive option on an already expensive lathe.

  19. #39
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    Doug

    I don't think it would cost much to add that feature to any lathe with half decent drive control gear, compared with the single tooth clutch.

    These were typically linked with a stop bar, along the lines you describe but mechanical, to trip the screw cutting traverse into neutral, thereby automatically and progressively cutting a relief groove. On a few of the fancier ones, the stop could be linked with the tool retraction mechanism, so a thread retraction runout was automatically produced --- nice !

    The single tooth clutch meant that the spindle could keep running at full speed in one direction throughout, while the tool ran back to the start at screwcutting speed

    If you tried to use carbide threading tips, the problem with the electrical option you describe where the lathe grinds to a halt under full cut, would be that -- unless the operator first turned a relief deeper than the finished thread -- I think you'd find the tip would need replacement between each pass !

    Even using HSS, I don't think the tooltip would survive long in threading, say, stainless steel. I can see it working OK in brass, provided the brake operated consistently.

  20. #40
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    The Holbrook Minor has a 3HP motor driving a Kopp Variator which in turn drives a two speed gearbox containing two fast acting electro-magnetic clutches and a brake. On stop, the motor and variator are disconnected from the gearbox by one of the electro magnetic clutches, and the brake is actuated. The only rotating mass is the output shaft of the gearbox the lathe spindle and threading mechanics.

    In reality it is very easy to just to use the standard controls, a joystick for forward/reverse and the tool-slide withdrawal lever. With the stop rod system, or just threading manually, you just flick the tool-slide withdrawal lever and the tool is clear of the threads. The lever works equally as well with internal or external threads.

    The other Holbrook models, earlier and contemporary had excellent threading mechanisms. Threading was one of things they were famous for, (in the UK). The old C10 had something like 60 inch threads and 90 metric threads attainable quickly. The very old B8 is a sad thing to see for sale, as it invariably means that someone has died. It is usually the only way the owner will part with it.

    With modern electronics available, I am actually very surprised that the Holbrook stop rod system is not available on even the low end import lathes

    [ 11-01-2007, 05:05 AM: Message edited by: Doug Neaves ]


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