Centering work in a 4-jaw chuck - Page 2
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  1. #21
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    I eyeball the chuck lines to near center with holding the part, then roll chuck watching that part roll to and from my my tool holder or the bit I happen to have mounted to see what ever, then with the part farthest away crank the closest jaw to error to take about half that amount, Then set an indicator, most often I am .015 or so off so the final adjustment is quick and easy.
    Roll and take half the error with watching the indicator.

    I have just eye balled a part to very close with far and take half a few times , then took a skim cut to see the hit on one side , then moved half what it took tho make half a score cut half round the part.When you make all around with perhaps a .001 feed that is very close...But with using an indicator is best.

    *Good to know you can break a jaw screw with over tightening and they cost high bucks.

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    Use a QC post tool holder as a reference for halving the air gap. Ordinary one with a parallel bar in it works OK but you may have issues with the sight-line.

    The drill holding block for the Dickson type is ideal for the job as its nicely made and perfectly rectilinear. Just drop it in parallel to the bed and have at it. Touch off using the dials or DRO will get you to a thou or so so who needs a DTI for ordinary work. With square or rectangular stock you can do it directly in two moves per axis by using the dials or DRO to measure the error between opposite sides then setting the slide so you only have to wind it up against the block.

    If you are one of those heathens who regularly work with the tool post at an angle touch the drill holding block off against the tailstock to align with the bed.

    Simples.

    Only took me about 15 years to twig that one of the "I'll never use them" drill holders that came in the package deals when working up past the mandatory minimum of 16 tool holders without taking out a mortgage for factory fresh could actually be useful. Things are about twice as hard as a woodpeckers' beak so re-machining into a more useful shape wasn't gonna happen.

    Clive

  3. #23
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    This is a very heavy duty Skinner 609 four jaw chuck in about 4 3/8" diameter. The chuck is intended to hold small round parts solidly in small lathes and cylindrical grinders. The jaws are the width of a standard 8" chuck, so they offer very little offset without the jaws touching, but makes truing a round part pretty quick.

  4. #24
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    Quote Originally Posted by thermite View Post
    Meah.. see Post #16.

    When the handles on two chuck keys wudda been wot? Four feet apart and more, plus 25 and more foot stroll around the lathe to get AT one of them?

    No gain!

    It was easier to use the "Jog" button and just one...

    I got pretty good at feathering a 1/2" drive impact wrench when dialing in parts on a 54" Boolard.

  5. #25
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    Quote Originally Posted by Curt Brown View Post
    Anybody who tries to center work in a 4 jaw without using two chuck keys and a dial indicator is wasting time. Quit iterating!
    I routinely dial in a 12" chuck in under (1) minute using only (1) chuck key.

    Your Left hand is moving the chuck around (out of gear, it moves very easily)

    ....and your feet should stay planted firmly on the floor.

  6. Likes Limy Sami, Demon73 liked this post
  7. #26
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    Quote Originally Posted by Curt Brown View Post
    Anybody who tries to center work in a 4 jaw without using two chuck keys and a dial indicator is wasting time. Quit iterating!
    I dunno. Ask Adam Booth and Keith Fenner, two of the fastest guys on 4-jaw chucks that I've ever seen. Neither
    of them use two keys. I've tried the two-key idea and I just find it awkward.

    It's pretty clear from the range of replies in this post that there's more than one way to skin this cat. In the end the
    best method is the one that works for you. As long as you get speedy, consistent results nothing else matters...

  8. Likes JCByrd24 liked this post
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    Thinking about dialing the part in is probably worse than just doing it by trial and error. With the indicator against the surface to be centered, roll the chuck one whole turn and watch for the maximum deflection. Lift on the indicator stem and observe which way the needle turns as you lift it, so that you know which direction 'maximum runout' is. Remember this for a few seconds, as you will keep refreshing your memory with each rotation of the chuck. Then apply some pressure to one of the jaw screws nearest the maximum runout and see if the needle moves in the opposite direction of 'maximum runout'. Don't bother thinking CW or CCW, just observe the rotation direction of the needle. If you are making it worse, then turn the screw the other way. Adjust the jaws in opposing pairs, using only small adjustments at a time if the part is wanting to fall out of the chuck. Keep halving the error. You will notice the runout on the other pair of jaws may be unequal, so then switch to adjusting those pairs until they get much closer to equal runout. Keep on hopping back and forth on jaw pair adjustments and pretty soon you will be into the fine adjustment phase. Keep halving the error until it becomes insignificant.

    I've only ever used the two wrench method with a 3 jaw combination chuck, as one can adjust the max runout jaw while keeping the scroll somewhat tight on the part so it doesn't fall out of the chuck.

    One handy dial indicator 'tip' is a wire ring. For example a piece of MIG wire Loctited into a hole in some other tip, and then bent into a full circle, maybe 1/2" in diameter. You can twist the wire around itself to stiffen the loop. This wire will be more forgiving if there is an interruption for the indicator to pass over, as it will not so readily drop into the notch and get moved. Such a ring will actually ride over a hexagon or a square bar without continually lifting it by hand.The wire can also get into a quite tight corner, like the register of an electric motor endbell which may have notches and scant areas where the normal ball indicator tip will not fit.

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    Quote Originally Posted by donie View Post
    This is a very heavy duty Skinner 609 four jaw chuck in about 4 3/8" diameter. The chuck is intended to hold small round parts solidly in small lathes and cylindrical grinders. The jaws are the width of a standard 8" chuck, so they offer very little offset without the jaws touching, but makes truing a round part pretty quick.
    Aaaand the point is????

    Nice Lathe though.

  11. #29
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    Quote Originally Posted by LKeithR View Post
    I dunno. Ask Adam Booth and Keith Fenner, two of the fastest guys on 4-jaw chucks that I've ever seen. Neither
    of them use two keys. I've tried the two-key idea and I just find it awkward.

    It's pretty clear from the range of replies in this post that there's more than one way to skin this cat. In the end the
    best method is the one that works for you. As long as you get speedy, consistent results nothing else matters...
    Agreed, I made a second key at one point and it never got much use, requires 3 hands. The "key" is not to tighten too much when you're closing in. It all clicked for me when watching Adam Booth, his saying "tighten the highs, Loosen the Lows". That and realizing the Lows are when the hand moves Left on the indicator (CCW). Loosen, Lows, Left. I'm just a hobbiest but I have no problem remembering how to do it after days or weeks outside the shop now, and I'm not that slow either.

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    Picking up on several prior points;

    - air-gap worked best for me at 9 O'clock. Wasn't happy with the HTRAL chalk trick, even when still at school. Initially spun a lantern TH around and used the arse-end of the Armstrong-Williams as reference, Later added a purloined darning needle outta mum's sewing kit, then an "ALNICO" magnet salvaged out of a table-radio speaker to hold it. The tiny, strong "rare Earth" magnets of today weren't "there" yet.

    - That 0.010" typically was halved to about .005". Day job, later-on, that was good enuf for new work, such as a 100 HP DC motor armature shaft as the raw stock was HRS alloy, rough surface, not perfectly to begin with - another pair of reasons to not introduce a then-very-COSTLY and fragile DI to waste time and risk the health of what one might need on some OTHER job.

    - The 9 O'clock was 'coz I added a sheet of white 3" x 5" card-stock, then a small cosmetic mirror - again outta the lady-goods section at the dime store. At 9 O'Clock, I could lay it right under the gap, have a cleaner and less eye-confusing background for my eyeshot of the gap than a grubby old lathe bed.

    Gave this more attention, 'coz it was for "picking up" on existing diameters for repair work. Considering the size, tolerances, age, and condition of the lathe, the chuck, and needs of mining or railway goods? It was all that was needed.

    A DI, OTOH, wasn't owned by about the lower third of us. Not when a Machinist First still made less than five bucks an hour (we started @ $2.13, Union Scale). Use of a "company" DI meant easily a 200 foot r/t walk to the tool crib and a few minutes to get the minder there to do the check-out and return paperwork.

    Hardly ever bothered. Few did, as the Shift Foreman (and our own Union Brothers) figured that sorta s**t was for pussies as didn't know their craft.



    Got a grand blessing of DI in the box NOW. One-thou Chinese disposables clear down to 20-millionths Mahr with batteries and ten-millionths Hamilton without, "many" types of holders and mag bases.

    Still rare to bother for a 4-J setup. Unless, as said, having to "pick up" on an existing surface or bore.

    2CW

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    Quote Originally Posted by litlerob1 View Post
    Aaaand the point is????

    Nice Lathe though.
    AAAnd point being, a type of 4jaw chuck that is quick to adjust to true center by design. The lathe is a high speed machine, where as an item like a special chuck such as this will go a long way combating deflection, and internal shift, with the resulting problem of the part being bigger on the end

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    Quote Originally Posted by Curt Brown View Post
    Anybody who tries to center work in a 4 jaw without using two chuck keys and a dial indicator is wasting time. Quit iterating!
    What a f'in nitwit!

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    Quote Originally Posted by moonlight machine View Post
    What a f'in nitwit!
    "Iterating" is the general case for masturba... n'er mind..

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    Quote Originally Posted by donie View Post
    AAAnd point being, a type of 4jaw chuck that is quick to adjust to true center by design. The lathe is a high speed machine, where as an item like a special chuck such as this will go a long way combating deflection, and internal shift, with the resulting problem of the part being bigger on the end
    I'm sorry, I only see a small 4J on a Hardinge. I don't see anything special. Anyone who uses a 4J regularly deals with the same issues you're pointing out, every single time they use it. Big-Small it's a Chuck. I don't see anything special.

    R

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    If your stock will balance lengthwise on the bottom jaw, use that as a guide and bring the jaw towards you up to touch the stock. Rotate the chuck 90 degrees and repeat, bringing the third jaw up to the stock. Rinse and repeat until you're all the way around. With a little experience you will be within .020. It's up to you if you want to put an indicator on it then or just run it as is.

    Better yet, get a 3 jaw with gripper jaws. You can always shim gripper jaws to grab finished surfaces but you can't add grippers to smooth jaws.

  18. #36
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    anyone heard from Forrest recently? A bit worried about him, he hasn't been on any forums for a while now which is not like him

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    Quote Originally Posted by litlerob1 View Post
    I'm sorry, I only see a small 4J on a Hardinge.
    Hard-dinkey?

    Go and warsh your mouth out with DTE Light.

    Quickly!


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    Quote Originally Posted by thermite View Post
    Hard-dinkey?

    Go and warsh your mouth out with DTE Light.

    Quickly!

    Sorry, the color and shape of the Headstock is the same----it's a 10EE. I didn't notice the Tailstock lever.

    R

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    Quote Originally Posted by J.Ramsey View Post
    Years ago back around 2006 IIRC Forrest Addy posted an excellent tutorial on centering work in a 4 Jaw chuck and I printed it off and saved it in my laptop, well several years ago my old laptop crashed and I have since lost the printed copy.
    I searched PM for about an hour and cant it find anyone know or care to point me to it?

    I believe you are referring an Article Forrest did in the November/December issue of Home Shop Machinist,way back in 2004.
    It is an 8 page article and is very well written,as Forrest always does.
    PM me if you can't get it off the Internet,can e-mail it

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    Funny enough, every time I read someone calling me a pussy for using a dial indicator, it reduces my overall opinion of the guy.

    I don't really care if you worked for almost nothing, on a dirt floor, in the dark, because the boss made you buy your own candles. We're not going back to that crap. We have evolved, and have access to better and cheaper tools. And better work conditions.

    Crawl back into your nice warm fuzzy feeling memories of living a Bull Of The Woods cartoon, Thermite, or act like an evolved human being.

    I, on the other hand, am THANKFUL, that I had harder times deciding WHICH indicator to choose from, in my well lit, comfortable, well paid job.

    I'm happy enough to reach for an indicator to show me that he taper attachment is actually moving, or that the part is actually moving where I want it in the chuck.

    I know well enough what CAN be done with crude tools, when it's all you have, I also know that I don't have to live that way, in this enlightened, well equipped age.


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