Lathe Taper when boring/turning
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    Default Lathe Taper when boring/turning

    When Boring or turning I'm getting unwanted taper in 3 to 3.5" say tailstock end is .650 i.d. head end will be .648 so .002 in 3" but If I run in reverse there is no taper cutting on the backside

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    Holding the work in the chuck only, or between centers?

    Sent from my Pixel 2 using Tapatalk

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    5c collet or 3 or 4 jaw it doesn't matter kinda stumps me

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    Quote Originally Posted by Gerichchokes View Post
    5c collet or 3 or 4 jaw it doesn't matter kinda stumps me
    You didn’t provide much info, but all other factors aside, and just going on what you did include, it could be the following; poorly supported work, say 3/4 dia, just held in a collet or chuck sticking out 3.5”, no tailstock support, and the headstock misaligned away from the front (rotated counter-clockwise looking down at the lathe from above), say .001 in 3”




    Work deflects away from the tool, so that unsupported end would be larger by .001 with a “perfectly” aligned headetock, and it would be smaller by .001 at the chuck or collet. Add the mid-alignment, and it’s .002 on the front side cut, and it zeros out on the backside.

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    Had an oddie a while back when doing an interrupted cut. The compound slide hand crank on my big lathe is not well balanced. I caught it slowly rotating heavy-end-down after scratching my head over a slight taper. A continuous cut, even a heavy one, did not provoke the same behavior.

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    Appreciate your reply, its .812 diameter sticking out 1.750, if I take a spring cut it doesn't really take and more material

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    Quote Originally Posted by Gerichchokes View Post
    Appreciate your reply, its .812 diameter sticking out 1.750, if I take a spring cut it doesn't really take and more material
    What material and cutting tool? If you are cutting say 4140 pre-hard with a slightly dull insert you might get deflection on that stickout, and not get a chip on a spring pass, try it with a sharp hss tool and aluminum.

    Just some other thoughts (my apologies and don’t take offense if you already eliminated all this!), Is your backside cut done with the same tool and holder? Does your lathe have a taper attachment, and is everything tight? Is the cross slide nut in good shape and snug? Are you taking up backlash properly for both cuts?


    Obviously, a proper survey will sort this out, but just a few things to consider maybe.

    Oh, and what kinda iron are we talkin about here?

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    Clarify what you meant by:

    "but If I run in reverse there is no taper cutting on the backside"

    Do you have a rear toolpost and inverted tooling?

    Or did you only mean reversing the direction of FEED, spindle still rotating same direction?

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    Quote Originally Posted by pat_j0nes View Post
    Holding the work in the chuck only, or between centers?

    Sent from my Pixel 2 using Tapatalk
    Tell me, how in the hell can you bore a hole between centers?

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    Quote Originally Posted by Jim Kobe View Post
    Tell me, how in the hell can you bore a hole between centers?
    Trade secret? Or simply not well-known?

    But I happen to have a lathe as can DO exactly that and easily so.

    Rack operated, not screw, "capstan" tailstock ram. Hollow. Like a milling-machine's spindle. Has tapers fore AND aft as can mount a sort of "gun drill" rig inherently.

    Open center roller-bearing at the pointy-end, tube/"pipe" profile ELSE inverted cone to pick up on the work - depending on whether starting with tubular or solid - does the rest.

    Clever guy, Henri Rene Bruet.


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    Quote Originally Posted by thermite View Post
    Trade secret? Or simply not well-known?

    But I happen to have a lathe as can DO exactly that and easily so.

    Rack operated, not screw, "capstan" tailstock ram. Hollow. Like a milling-machine's spindle. Has tapers fore AND aft as can mount a sort of "gun drill" rig inherently.

    Open center roller-bearing at the pointy-end, tube/"pipe" profile ELSE inverted cone to pick up on the work - depending on whether starting with tubular or solid - does the rest.

    Clever guy, Henri Rene Bruet.

    And how common are these, how many members on this forum
    has one of these ?

    Thermite, show us a picture of yours, I’m curious.

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    Quote Originally Posted by vonleyser View Post
    And how common are these, how many members on this forum
    has one of these ?

    Thermite, show us a picture of yours, I’m curious.
    Several of us have them. Several more HAVE had.

    Nary a mystery to it. Just look it up. The patented TS with nice drawings and explanation.

    Or the fotos on Tony's site - same model as my one is on the lead page, my tracer long-lost.

    Cazeneuve HBX360 Lathe

    Or the very lathe itself, fotos still hanging on Milacron's not updated website:

    Procyon Machine

    Or threads on PM, two capstans Milacorn compared at some length - the HBX-360-BC with one of his uber-Schaublins, "Right here, on PM", and over a period of about two years. He came down on the side of the Schaublin for ease of conventional use. I saw merit in the hollow-tube TS of the HBX for UNconventional use.

    Those PM threads were a major part of what SOLD it to me in the first place!




    How common?

    Well... Cazeneuve built 40 or 50 thousand of the all-manual "HB" lathes, factories in France, Spain, Brazil and Japan, before switching-over to the present-day "teach in " manual/CNC hybrid with the Seimens brains.

    How many had the optional capstan tailstock? Surely not ALL of them. Cheap it was never.

    But neither are they super rare.

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    Recently I adjusted raper out of my Nardini headstock. I used the jackbolts under the headstock to move it until I had zero taper in 8". If your headstock does not set on the V way of the bed look for jackscrews to adjust the headstock. If the headstock sets on a V way of the bed the initial alignment was created when the headstock was scraped to the bed an there is no provision for adjustment.

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    Quote Originally Posted by Illinoyance View Post
    Recently I adjusted raper out of my Nardini headstock.
    Good of yah. But did ICE deport the sick bastard back to Brazil? The raper. Not the Nardini.

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    What I meant by running in reverse is cutting on the backside of the part, o.d. or i.d. the material is 12l14 so it's pretty soft

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    One effect few consider is that the saddle can rotate on the bed ,the point of rotation generally being some location frictionally opposite to the saddle drive (rack) pinion...In a new lathe ,the V ways /guides of the saddle are always relieved in the centre part and bear on the bed at the ends ......when this bearing wears away with use ,the entire length of the saddle v then runs on the bed,all the time the extreme ends of the vee s are wearing at the sides ,so the saddle can rotate within these limits ......as more wear is caused by feeding towards the chuck ,the rearward direction stays relatively true for a much longer time......This kind of wear is difficult to grind away because so much needs to be taken off.....which is where the plastics like Turcite are needed.

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    Quote Originally Posted by Gerichchokes View Post
    What I meant by running in reverse is cutting on the backside of the part, o.d. or i.d. the material is 12l14 so it's pretty soft
    Aright.. "avoided, so far" is "on WHAT lathe?" ...and perhap because you must, but .. significant taper on a mere .810" part with only 1.75" projecting in steel cheese, AKA 12L?

    That only happens with TP operator side of CL and does NOT happen with TP far side of CL?

    Tells me you are likely running a clapped-out 1920's Niles.. or an Asian "LSO" shipped from the factory already in "simulated" wore-out condition 'coz there ain't No Fine Way it will live a hundred hard years to earn genuine battle scars on its own merit. Or lack-thereof.



    - Get you an ignorant Cee-clamp that can reach topslide to saddle bridge underside.

    - Set up for a modest, but "real", cut, not a "spring" pass.

    - CLAMP the Mike Foxtrot topslide so it cannot move.

    - Same again with the compound, smaller clamp. or tighten the gib to froze-stiff.

    - Run your pass. "front" side. "Normal" - everything nailed-down but the long-axis travel.

    NOW see if it exhibits a taper. If so, your TP or compound may have rotated or the toolholder been forced below starting height.

    A photo of your TP engaging the work, chuck in the picture, would help, BTW.

    There are only a few "right"ways to set that up. But a much larger number of "wrong" ways.

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    Running between centers means the work is held between centers, one in the headstock and one in the tailstock. Bsic terminology!

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    Quote Originally Posted by Jim Kobe View Post
    Running between centers means the work is held between centers, one in the headstock and one in the tailstock. Bsic terminology!
    And yet you can't spell "basic"

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    Quote Originally Posted by Jim Kobe View Post
    Running between centers means the work is held between centers, one in the headstock and one in the tailstock. Bsic terminology!
    Just answer the why, Azzhole.


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