Metal Lathe

Discussion in 'Workshop Tips and Secrets / Tools' started by ToddK, Nov 30, 2019.

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  1. Dec 5, 2019 #61

    Topaz

    Topaz

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    My own lathe is, quite literally, from the '20's, and I don't mean next year. I forget the make and model; it's been in storage for a long time since I can't fit it in the shop. Weighs a solid "ton" for the size, but is worn and sloppy as heck. I can still get good parts from it, if I'm willing to take my time and cut-measure-cut. Someday I'll try and get it tuned up, but that's not likely to be any time soon.

    A small CNC mill would be nice.
     
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  2. Dec 7, 2019 #62

    Aviacs

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    For "airplane parts" the only issue with many/most pre-ww2 lathes is the slow speeds. Many top out in the range from 600 - 800 rpm. Not a lot of fun if most of the parts will be "small" and aluminum or other free-cutting materials.

    If the bearings are good, smooth, and tight, they can be run faster (change of motor sheaves, or over-drive with a VFD) with good light weight spindle oil, but not by much.

    OTOH, If you chuck up something huge in difficult material, they can be a delight with HSS positive rake (not carbide) tools. Ideal if you want to turn out full size repro steel cases and barrels for that replica rotary engine. :)

    smt
     
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  3. Dec 9, 2019 #63

    Jeff Higgins

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    I have two lathes which are my bread and butter as a gunsmith. One is a combo Smithy and the other a Bolton. I prefer the Bolton because of its 36” between centers but use the Smithy when I need the larger spindle bore.
     

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  4. Dec 9, 2019 #64

    ScaleBirdsScott

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    What kind of gunsmithing type tasks do you end up doing with those types of tools? Barrel threading and so-on?
     
  5. Dec 9, 2019 #65

    Jeff Higgins

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    Everything and anything from complete barrel tapering and contouring, threading, cutting tenons to making custom parts. The Smithy has a rear spider I made so that I can indicate barrels concentric and true before chambering and reaming them.
     
  6. Dec 9, 2019 #66

    Hot Wings

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    This works with a good ridged lathe.
    For The average hobby grade lathe this generally means that the last cuts do nothing and the part ends up oversized. This is where experience with a particular machine becomes important. Often it works well to cut to within (just random numbers) .010" of the final, take one more cut of about a third, measure one last time. Compare the last measured cut to the calculated cut - for example it may be .002 larger than desired/calculated/expected.......... and then take a healthy final cut, .002" more than is needed per measurement.

    .0005" on a hobby machine!? Most hobby type owners can't even measure that well.
     
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  7. Dec 9, 2019 #67

    blane.c

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    Your depth of cut on last cut will depend on your experience with your lathe and the material you are working with. Nothing is absolutely rigid there is always some kind of springing going on especially the farther away from the support you go.

    For older or vintage lathes some people on some lathes that will allow it without a lot of other undue modification have simply moved the headstock and shimmed it true farther down the bed-ways. Since the full length of the lathe is seldom utilized it works well for many as the carriage and tailstock are now in a less used and therefor a truer area of the lathe ways. There is that length of lathe bed sticking out to explain to friends and family … just blame it on commies, socialist's, space aliens, you know the usual suspects.
     
  8. Dec 9, 2019 #68

    BBerson

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    I can't measure that either. But each progressive smaller cut makes a smoother finish by just taking the ridges.
    It's like sandpaper grit, start with 40 grit, then 80, then 220, 400, 800, etc, to whatever finish you want. No need to measure it unless you need a press fit.
     
  9. Dec 9, 2019 #69

    stanislavz

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    Nope. Its not lile that. Cutting do have minimum deph, which is about 3-5 radiuses of tool-tip. Anything less - is impredicable.
     
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  10. Dec 9, 2019 #70

    BBerson

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  11. Dec 9, 2019 #71

    Jeff Higgins

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    It’s easy to hit a final dimension if you know your lathe and tools. I typically use carbide inserts which only leave a nice finish once you take a heavy enough cut to reach the chip breaker which is usually indicated with the inserts. If I have a final dimension I need to hit, but say I still have .045 to remove, I’ll split that up into two passes (.0225) to hit my final dimension every time. If I were to take .040 off and then go back for the final .005, the finish will look like hell and my dimension won’t be precise.
     
  12. Dec 9, 2019 #72

    blane.c

    blane.c

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    Carbides are like that.

    So home shop'rs often like HSS or M2 - AL ( http://cdcotools.com/ ). You can put a keen edge on either and sneak up on a finish. We don't use the lathe frequently enough to know exactly how much is going to work on what with the carbides.

    Of course for something hard and finicky I'll sharpen a carbide like a HSS and use cutting oil and sneak up on a finish anyway, if careful the edge won't crumble till I'm done.
     
  13. Dec 9, 2019 #73

    Jeff Higgins

    Jeff Higgins

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    Very true that most people prefer HSS when it can be used. I’m mostly a fan of carbide inserts because working with firearms is mostly hardened steel or I have to hog off some material, like when turning a barrel blank to a contour.
     
  14. Dec 10, 2019 #74

    blane.c

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    I am going to try some of the M2-AL it is supposed to be like cobalt but cost just slightly more than HSS. Not that it will replace carbide but it will cut stuff that is a bit harder or normal stuff a bit faster.
     
  15. Dec 10, 2019 #75

    thjakits

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    Someone mentioned mill OR lathe...

    Well, maybe you can have both - of course depends on what you want to do with either...

    I'd look into a set-up that mimicks the white paper from Tormach (small CNC stuff).
    I attached the 1st paper that was available on that subject - subsequent versions are more into CNC related aspects, I think this one is most clear about the idea - relating to the manual/analog operation...

    Their research showed that most combination drill/mill/lathes are actually wrong.

    First - changing from one mode to the other takes way too long - and usually the mill ends up being too small.

    Their results show that - usually - you would turn stuff that has to fit inside milled stuff!!
    So - their biggest CNC mill has a lathe attachment (which also can work as a 5th axis) that fits onto the mill!

    IF you copy this into manual/analog set up - you would end up with fairly good mill/drill and table-top lathe, that would fit on the mill table! With a indexing and lock device you could now do fairly complex stuff!

    Of course a Top-Tormach set would be nicest, but if you do not have the big bucks - with craigslist, used and elbow grease one could get a nice set-up....

    https://www.tormach.com/our-story/

    NOTE: I have NO connection to Tormach at all - but they do have interesting documentation!
    thjakits
     

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  16. Dec 10, 2019 #76

    blane.c

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  17. Dec 11, 2019 #77

    thjakits

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    Well - I am still dreaming of a TOrmach - though I did stumble on a clip on youtube with a fellow that had an issue with Tormach and it cost him!! NOT exactly what I thought about Tormach....
    I think one would have to investigate thoroughly before plucking down the money!!

    thjakits
     
  18. Dec 11, 2019 #78

    ScaleBirdsScott

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    A bit unrelated but since we're bringing up Tormach thought I'd mention I've been looking into small CNC lathe/turning centers this week, as my other startup (that isn't airplanes) needs a lot of small lathe turned parts and, the cashflow points to financing a machine and doing the labor vs paying a shop (likely overseas) to do it. We're doing small batches, but need good consistency and control, but with the ability to tune things on the fly so it precludes really going and ordering 1,000 parts at a shot. We need to do like 10, 20, 100 at a shot. After some time and some experience with the products in the field, maybe we can lock in our design and go bigger but ultimately we're looking at needing to tune things for a year or two. So in-house seems like a good way to manage that.

    All that to say I found AutoMate CNC, which is a brand that looks like the CNC arm of the Smithy brand. All Chinese import stuff, but looks a good bit beefier than a Tormach and people have said that the owner is pretty stand-up even if they don't provide a lot of direct technical support. But is good about actual purchase and sales support and clear education on the product. So there's that. There's also Syil and a few other brands, that are basically importing machines all of the same designs. Same sort of deal with the Precision Matthews, Grizzly, Bolton, Jet, ShopFox, etc all importing variations on the same template of home shop stuff; but with price tags in the 10-40k range. Still they are machines that are actually designed to make parts with good quality at industrial scale.

    After all the research its very tempting, but we probably are not going to go that way; might just go with a Haas TL-1 or CL-1 for a small bit more money, as we're already working on getting a Haas mill and need these machines to be as plug-and-play as possible so can't afford to spend weeks working the bugs out of an import machine. Granted it's not the way I'm used to spending money, being the Yankee DIY type, who has built his own CNC machines, I like the idea of getting the most hardware for the buck and not paying someone else to tune it when I am within my means to do so. So I'd say for the budget minded home-shop that needs an actual production CNC (which isn't really in the scope of the homebuilder needing a manual lathe but still) these little AutoMate machines really seem to be a viable option if you're looking to step the game up.

    Something like this: https://automatecnc.com/products/lts5-lab-turn-cnc-lathe
    Or even like this: https://automatecnc.com/products/sl6-slant-bed-lathe-cnc-turning-center

    I think the niche Tormach is in has been getting squeezed lately as these sort of cheaper light-industrial import machines get better representation in the west, while the cheaper manual-to-CNC conversions are coming in at the bottom end and offering the true budget minded hobbyist a ground floor way to step into the game and go pretty far with it. Tormach needs to widen their range (which they have been with their MX series) but possibly look at also offering some of these larger more serious machines. And then they need to probably work on their customer support and service to compete with a Haas or similar.

    Of course this all is just ignoring that those who truly have the space and time on their hands can get used older CNC machines for a song as mentioned previously, and with a bit of elbow (and face/whole body) grease get one into decent shape from the looks of it. Some resellers even offer their own support and financing options.
     
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  19. Dec 11, 2019 #79

    Aviacs

    Aviacs

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    No arguments here, when the machine considered has a tool changer, bar feed, and parts catcher. :)

    OTOH, for families of small parts in runs under 100 pcs, it is not always clear that a simple old hand screw machine ("turret lathe") with a shop-rigged bar feed would not be about as fast & lots cheaper. OTOH, getting cnc conversant is invaluable in the modern age. Wish i had made time to catch up.

    For really good, cheap, cnc productivity on smallish parts, ignoring the prototyping options of a cnc engine style lathe, a gang tooled machine is fast and cheap. Essentially, the dedicated tooling is an extension of the program.

    Get past a few 1,000 pcs, and a multispindle screw machine will still walk all over a cnc lathe for productivity.
    Just for perspective. :)
    Then comes the argument: software is easier to change than hardware (tooling) though.

    smt
     
  20. Dec 12, 2019 #80

    stanislavz

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    For less than 100 parts with low complexity ie pulleys, spacers - use of template or copy attachement is ok. And more faster and precise then home-brew cnc. Just try to find an old Master. He will show you some tricks, how to do fast and nice in a kind of old days.
     
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