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    Default Looking for very slender live center

    Hi,
    I've come to realize that I need a live center (MT4) that has a point that will allow work on OD's as small as approx 12mm.
    The static holders I use are std. 25 mm and I have failed to find live centers that have a sufficiently reduced OD point to allow access for typically threading.
    Considering buying a live center with replaceable inserts and making my own in case I can't find anything.
    I generally work with light parts with low tolerance requirements, so this live center "tip" does not need to take up great loads.
    I have looked into Royal (US) and Rohm (GER), but I suspect there probably is an out of the box product for me somewhere. Cost not a big factor, I only need to buy this once:-)

    03-skp_01.jpg

    Thanks in advance for all tips!

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    Quote Originally Posted by Schjell View Post
    Hi,
    I've come to realize that I need a live center (MT4) that has a point that will allow work on OD's as small as approx 12mm.
    The static holders I use are std. 25 mm and I have failed to find live centers that have a sufficiently reduced OD point to allow access for typically threading.
    Considering buying a live center with replaceable inserts and making my own in case I can't find anything.
    I generally work with light parts with low tolerance requirements, so this live center "tip" does not need to take up great loads.
    I have looked into Royal (US) and Rohm (GER), but I suspect there probably is an out of the box product for me somewhere. Cost not a big factor, I only need to buy this once:-)

    03-skp_01.jpg

    Thanks in advance for all tips!
    Riten can make what you need for any of their live centers, and to very, VERY high standard.

    Cheap live-center "sets" with replacable tip options usually have at least one really skinny one - nothing special nor costly needed for half-inch stock.

    Puzzled, though.

    So long as a centre tip comes to a point, it creates its own clear space, even if it 'eventually' tapers-up to a high multiple of the work's OD.

    What sort of tooling are you utilizing that cannot work within that 'natural' ration?

    And how hard would it be to work with a DIY dead-center, utilizing a hardened shop-fab point, straight-shank, held in a TS-mounted drill chuck or collet?

    Or a bearing-ball - already wedding-night-dick hard- held in a female cup tipped center?

    Might be faster and cheaper to use a different toolholder than to have a centre custom fabbed?

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    Hi,
    Thanks for Riten tip!
    I haven't found all dimensions on the skinny CNC live centers that I've found, such as the Rohms picture above.
    Threading is the most limiting one I think - it looks like when my holder is to start threading at typ. Z1.0(mm)then it will require about 26mm of space towards the tailstock/live center. If the live center tip was a bit longer before it tapered out to full OD then it would work (for sure).
    The threading holder that I use Vargus) has got an internal cooling channel so I have not yet tried grinding an angle on the holder to give me more space. I don't use the internal coolant for threading, but considering connecting it up. I'm also a bit concerned that I need the rigidity in the holder, but I'm guessing it's overkill as it is.
    Still learning every day, maybe it's everyday practice to take a holder to the grinder to get the job done.

    Below is a picture of current situation, which clearly would collide. Maybe a set with replaceable inserts is the best way to go.

    received_390164606084031.jpg

    EDIT NOTE:
    Just had a thought.
    If I drill and tap a hole in the stock, put a custom "bolt" in it, then I could offset the point where the live center engages. Just a thought. Might work if I keep loading very low. Disastrous if it fails as the hydraulic tailstock would slide forward

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    The common kind of live centre with a point unit projecting from a relatively large diameter bearing carrier doesn't play well with small shafts. Especially in large taper mount sizes where the bearing and its carrier is sized for the hefty jobs normally done on such machines. You end up with a silly long point unit to get tool access between the job and bearing unit with corresponding lack of rigidity and degradation of accuracy.

    Although the general range of interchangeable point kit types do appear to have sufficiently slender centre points quality seems to be something of a crap-shoot. As usual with such semi-professional (at best) the price / market demand curve won't accept high, guaranteed, fully inspected quality.

    Best design for this sort of thing is the inverted type where the centre itself is tubular with the bearings inside carried on a plain stub on the end of the taper mount. Load carrying capacity is less than the conventional type due to the smaller bearings but they can obviously be made very slender.

    No idea if they can still be bought commercially.

    Believe the one I had dealings with was intended for small electric motor rebuild duties but it was certainly adequately accurate for light machining. That one had a simple ball in the centre at the front end of the spigot to take thrust loads and a basic magneto style bearing at the back to hold it all in-line. On an MT2 taper and around the same OD as the lathe tailstock barrel.

    If they are still made, and intended for machining work, I imagine the bearing arrangements would be more solid.

    I've several times contemplated making one on the bi-annual or so occasions when it would make a "why did I agree to do this?" type job easier.

    Decent quality needle roller with inner and outer races sitting on a plain end MT taper to carry the side loads with the same sort of single ball up front for thrust. Use a radius centre drill rather than the normal variety to form the bearing seats. Hardening the ball seats isn't really practical but if reasonably obdurate steel is chosen and lubrication ample it shouldn't wear out on my watch. For practical assembly reasons the bore in the rotating centre "tube" body for the needle bearing outer race needs to be a bit over-long. Hence it will self adjust slide a little to take up minor wear.

    For best accuracy it would seem wise to arrange some form of zero side thrust locking arrangement so that the unit can be mounted in the lathe headstock so the actual centre point can be formed in situ. My provisional plan was to loctite an alloy sleeve on to join the centre to the body. The sleeve could easily be turned off, after making the centre point true, before removing the unit from the lathe headstock.

    Clive

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    Quote Originally Posted by Schjell View Post
    Hi,
    Thanks for Riten tip!
    I haven't found all dimensions on the skinny CNC live centers that I've found, such as the Rohms picture above.
    Threading is the most limiting one I think - it looks like when my holder is to start threading at typ. Z1.0(mm)then it will require about 26mm of space towards the tailstock/live center. If the live center tip was a bit longer before it tapered out to full OD then it would work (for sure).
    The threading holder that I use Vargus) has got an internal cooling channel so I have not yet tried grinding an angle on the holder to give me more space. I don't use the internal coolant for threading, but considering connecting it up. I'm also a bit concerned that I need the rigidity in the holder, but I'm guessing it's overkill as it is.
    Still learning every day, maybe it's everyday practice to take a holder to the grinder to get the job done.

    Below is a picture of current situation, which clearly would collide. Maybe a set with replaceable inserts is the best way to go.

    received_390164606084031.jpg
    Meahh.. making a problem out of a solution?

    First-off, I'd have the stock you show in a collet, and with the shoulder near-as-dammit flush to the face of it.

    Now I do not need a centre at all.

    Second: I'd be doing the usual.. threading AWAY from any obstruction, up OUT of a blind bore, AND NOT towards any feature or barrier as was to be preserved .. that I had to sweat running past or into.

    To the right, in this case.

    So I didn't have to care when it ran off the end, either.

    IF.. I wasn't using HSS/Cobalt or Tantung-G .... where I can shape the tool any which way I needed to shape it?

    That method also no longer gives a damn how wide the tooling is ... to the open-air end ... where the center USED to be ... at the right side.

    CNC, so that should be a power workholder, not a manual chuck?
    "Win-Win" if all you do is shorten your stick-out, even if only for this op.
    Then you can shed the centre.

    Even better if you can use a die - or in the CNC case- a die head - instead of single-pointing at all. Faster that way.

    Lazy, Iyam.

    Cheap bastid, too.

    Riten don't do their magic for free.

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    An easy alternative is to switch to sandvik for threading.

    Their insert location system allows them to make a holder that has no back edge. Use in combination with a standard extended/double angle point centre.


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    Yeah, I clearly see what you mean!
    As for my current situation, I don't really have the luxury of replacing the chuck with a collet type. I make three different parts in a day typically, typically between 1 and 15 in a series. So I went with the straight collet shank solution that I grip with the soft jaws. It's ER32, so I can only take up to 22mm stock.

    I also get the point of doing stuff close to the chuck to avoid deflection and trouble. I was hoping to have a do-it-all-in-one-go with parting at the end of the cycle, but I see that this is not really feasible without a skinny live center. As it happens, I ended up doing what you suggest. Dividing it in to two ops where I move the set point (G54) after threading to avoid req. for tailstock support.

    Threading the other way you suggested is an annoyingly good suggestion! I will try this - as mentioned I'm still learning. 1,5 years and going - always something new to ponder upon - never gets boring!

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    Quote Originally Posted by Schjell View Post
    Yeah, I clearly see what you mean!
    As for my current situation, I don't really have the luxury of replacing the chuck with a collet type. I make three different parts in a day typically, typically between 1 and 15 in a series. So I went with the straight collet shank solution that I grip with the soft jaws. It's ER32, so I can only take up to 22mm stock.

    I also get the point of doing stuff close to the chuck to avoid deflection and trouble. I was hoping to have a do-it-all-in-one-go with parting at the end of the cycle, but I see that this is not really feasible without a skinny live center.
    It could be.. if you can waste metal more cheaply than time or tooling budget.

    Leave a sub-minor-diameter teat long enough to clear your fat tool-tip.
    Part THAT teat off first once threading is done.
    As it happens, I ended up doing what you suggest. Dividing it in to two ops where I move the set point (G54) after threading to avoid req. for tailstock support.
    Minimum overhang - work OR tooling - is sacred religion. Ever and always.


    Threading the other way you suggested is an annoyingly good suggestion! I will try this - as mentioned I'm still learning. 1,5 years and going - always something new to ponder upon - never gets boring!
    Threading "away from" WAS common..

    It is not ALWAYS in either of reverse, nor upside-down, given both LH & RH threads exist and either one may be internal OR external.

    "WAS" ..standard.. wherever... the dagone lathe was large and the work was heavy.

    All we chikn's had no other realistic option.

    1960's for me, but some of my mentors were already past 80 years of age, most were past fifty, and the Germans and Austrians had been in the trade since apprenticed at age fourteen.

    No "servo" spindles y'see. You just don't stop a large cone-head lathe and heavy work easily, rapidly, nor predictably!!!



    By threading "away from"?

    We did not have to, either!

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    How DARE you fat shame our standard live centers...you should be ashamed of yourself.

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    Quote Originally Posted by plastikdreams View Post
    How DARE you fat shame our standard live centers...you should be ashamed of yourself.
    Lighten up.

    "plastikdreams", is it?

    It ain't a d**k .... or a dildo...... or so we hope..

    Next thing yah know you'll be defying conventions as to short stick-out.. decide it looks so good out you can leave it out...

    Could get arrested for dirty-walking? Or get all hot and bothered over ball mills?

    More than one kind of trolling on the internet.

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    Quote Originally Posted by plastikdreams View Post
    How DARE you fat shame our standard live centers...you should be ashamed of yourself.
    Haha! Apologies, just annoys me everytime I'm working on stock anything less than an inch😂

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    Quote Originally Posted by Schjell View Post
    Haha! Apologies, just annoys me everytime I'm working on stock anything less than an inch��
    Hah!

    Wait 'til you get old ....and need a search party to prep for a piss!



    Speaking of "search party".. Google finds a high-grade version of one I have a REALLY CHEAP (Chinese?..) version of:

    CNC Precision Long Spindle Live Center ZLC S06006-MT3

    .. easily enough:

    CARBIDE POINT CNC High Speed Live Center | 60o Extended Small Slim - RTJ Tool Company

    Left foto. Dorian Tool. More of them on their own website:

    https://www.doriantool.com/wp-conten...NTERS_2016.pdf

    How's that for Mosquito-shagging slender?

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    NAKANE has some options. I have 3 of the standard LS models as they're the only ones I ever found available in North America.
    An MT2 in a MT2-MT4 sleeve might be an option. Small live centers need less pressure to spin too on small parts with a tiny center drill.

    NAKANE LIVE CENTER


    Other option may be a Long Point spring loaded center, some of them are fairly small but I haven't tried one yet.
    Spring-loaded, “Concentric” Live Centers | Riten.com

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    Check out Gepy, they have several options and will do customs.

    GEPY, fabricant de pointes tournantes et de quills | Gepy Papaux

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    Good that we are talking about quality name brand lives.
    When I was an apprentice old-timer told me that a center will take off the TIR from one side and leave it on the other side.

    I have always held the premise and have solved many tooling problems with demanding that a live center error should be less than half the part tolerance.

    You see unbranded live centers advertised too .005, in my opinion, is good for allowing .010 parts
    ->.0002 good for a half thow.

    I think it is best to buy a small point live center rather than a multi-point one.

    Good lives are rated .0001 and 50 millionths, and most often they run better than advertised.

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    Quote Originally Posted by SND View Post
    Extended "CNC" point or not, those ones are just nice all-around. Very nearly the same fit as a basic Dead Centre.

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    Quote Originally Posted by thermite View Post
    Hah!

    https://www.doriantool.com/wp-conten...NTERS_2016.pdf

    How's that for Mosquito-shagging slender?
    Haha! Thanks again - Love the Dorian brand, never thought of checking them for live centers! Will definitively get a quote there! I remember coming across a fancy dampened 16 thousand dollar Dorian Boring bar once! Had to read it twice to believe it. It had an incredible L/D ratio, but that price tag made me chuckle!

    The Sanyo link that another guy posted here is also very interesting. I'm spending the better part of a day finding this live center, but it's hopefully going to solve 99% of the jobs I do.

    Best part of running a business is buying tools, never get fed up with it, however my two colleagues in the office end of things might disagree

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    Quote Originally Posted by Schjell View Post
    Haha! Thanks again - Love the Dorian brand, never thought of checking them for live centers!
    .
    .
    .
    I'm spending the better part of a day finding this live center, but it's hopefully going to solve 99% of the jobs I do.
    Well.. Hem's sake. LOTS of folk carry "CNC" extended-nose extra-clearance LC's. But if it means that much, buy the $500 Dorian one. Riten's better one is probably HIGHER. See also "Stark". Good specs. Usually a tad less coin than Riten. Skoda is another value-for-money manufacturer. The Czechs usually ARE.. most anything mechanical.

    I don't operate so I NEED that stuff that often, if even ever [1].
    Cheap is good enough for "just in case". Dead-centers and pink slime do me OK as well.

    LONG NOSE N/C Live Center<br> Morse Taper # 3.


    One noxious troll even made an up Your-Tubes vid claiming he had NEVER seen work run 'tween centers on a Monarch 10EE in over forty years.

    Go figure anybody as ever got near a lathe had led such a sheltered life?




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    Quote Originally Posted by gregormarwick View Post
    An easy alternative is to switch to sandvik for threading.

    Their insert location system allows them to make a holder that has no back edge. Use in combination with a standard extended/double angle point centre.

    Hi Gregor!
    Tried to make my Vardex holder look more like the Sandvik one on your picture
    Not sure if it's strong enough anymore; worst case it's a 300 buck holder down the drain!
    Hopefully fine, there's still plenty of steel to support the insert (I think).

    img_20211018_160542.jpgimg_20211018_160536.jpg

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    Quote Originally Posted by Schjell View Post
    Hi Gregor!
    Tried to make my Vardex holder look more like the Sandvik one on your picture
    Not sure if it's strong enough anymore; worst case it's a 300 buck holder down the drain!
    Hopefully fine, there's still plenty of steel to support the insert (I think).

    img_20211018_160542.jpgimg_20211018_160536.jpg
    Pretty standard practice TBH, it will get you through as long as you're not cutting big threads, or marginal on helix clearance (which tries to pull the insert off-axis). I have a few older ISO holders that look like that

    Sandvik's system has locating grooves on the bottom of the insert so it only needs one shoulder for the insert to pull up against, and the groove locks it in position. The holders are more expensive than ISO and so are the inserts, but it's a better system that is worth the extra cost IMO.

    As far as centres go, there are plenty of well made live centres available. I mainly use Rohm, but I have a few Korean or Taiwanese ones that are just fine. Bison are fine too at a lower price point. Most of the US brands are a pain to source over here (Riten in particular, I have one of those spring loaded ones and I had to jump through hoops to get it). MSC carry some Royal ones, but just the basic range. No idea about Nakane.

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