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    Default Cross slide lock.

    I have a Vextrax Lathe. it's a good machine. Has all the bells and whistles. The lathe is
    extremely accurate . I have a 6 jaw adjust tru, Bison chuck on it. I would like to grind
    the jaws on this chuck. Reason is with a ground shaft , after indicating in , has about .004
    -.005 run out at 12 " . I did all the instalation of the chuck corectly, took cut on backplate before installing chuck.

    The reason for this post is I have a DRO on this machine and the scale is covering the
    cross slide lock.
    I have a Themac tool post grinder , and i want to lock the cross slide while grinding.
    Anybody have any ideas? I know I could tighten the gib , But thats not right.
    I was thinking of making a lock on the front of cross slide, Attach to where the follow rest is and make something to lock it to the cross slide. Please give me any input on this. OR am i making too big a deal of this.
    Thanks, Ken Livenood

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    How do you plan on making adjustments on your grinding cut if your cross slide is locked? Try posting in the General Forum page.

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    Quote Originally Posted by Hothead View Post
    I have a Vextrax Lathe. it's a good machine. Has all the bells and whistles. The lathe is
    extremely accurate . I have a 6 jaw adjust tru, Bison chuck on it. I would like to grind
    the jaws on this chuck. Reason is with a ground shaft , after indicating in , has about .004
    -.005 run out at 12 " . I did all the instalation of the chuck corectly, took cut on backplate before installing chuck.

    The reason for this post is I have a DRO on this machine and the scale is covering the
    cross slide lock.
    I have a Themac tool post grinder , and i want to lock the cross slide while grinding.
    Anybody have any ideas? I know I could tighten the gib , But thats not right.
    I was thinking of making a lock on the front of cross slide, Attach to where the follow rest is and make something to lock it to the cross slide. Please give me any input on this. OR am i making too big a deal of this.
    Thanks, Ken Livenood
    If the compound is still in use, there's your adjustment for the McGonegal. Set it to "the usual" angle and one dial-thou giveth one-tenth of.

    BFD. You ain't gonna move MUCH. And you will have a ring on those jaws?

    No need to make a problem out of a solution. Wore-out junker lathe trick works just fine on a nicer lathe.

    Lock the silly slide wih a Cee-clamp, woodchoppers parallel clamp, or a big-ass Kant-twist.

    Do the do. Go use the 6-J.

    Worry about a more CONVENIENT top-slide lock some other day.

    This is a one-time exercise. Monkey-patch is permitted.

    Or so you hope and pray it is "one time"? Scroll-operated chucks being NOTORIOUS for localized deviations off the back of over-stress and damage at a given diameter?

    And SIX jaw chucks being MEANT only for thin tubing, rings and such as are too easily distorted by fewer points and higher clamping forces?

    AND NOT as a 3-Jaw nor 4-Jaw (roughly DOUBLE the ultimate grip of a 3-J) substitute, either one?

    Put another way.. if that is your ONLY chuck, you are not in a good place.

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    The first thing I do after installing a DRO to the back side of the cross slide is to finish by making a 90 degree angle slide lock. Where they usually stick a slide lock is right where the DRO blocks access, as if no one ever had a problem before and engineers never heard of this.
    They drill and tap a hole horizontally from the tailstock side straight into the rear gib's dovetail area, where the taper gib slides to adjust, then they make a bronze or hardened steel plug that slides in the hole with an angled inner end that matches the gib's angle. When you tighten the socket set screw it pushes that plug which pushes the gib against the inner dovetail slide, which increases the friction between the taper gib and the inner slideway so that the slide is locked to a greater or lesser degree.
    Of course with the DRO across the head of that screw it's blocked!

    So I mark where this tapped hole's position is on the top of the cross slide and drill/tap a converging hole vertically between the place where the end of that plug is and the outside edge of the slide's rear surface.
    Then I make a new plug to replace the original, out of a dowel pin, matching the angle of the original where it contacts the gib and angled 45 degrees at the other end so it's rear terminus is under the new hole.
    Finally I make a new plug that matches the new horz. pin's rear 45 degree surface, and has a short length with a 90 degree flat at the top.
    Now a short setscrew that has the head pointed straight up, and flush with the cross slide's top, is simply tightened the same as the original screw's was. A dab of grease where the two 45 angles meet and they make a 90 degree push as before, but the DRO is now not in the way anymore.

    I've done this to at least 5 or 6 lathes and they are all effective. On the big Sculfort heavy lathe I installed two such screws because the tapered gib there is about 1/2" thick there at the operator's end and it never had any lock at all originally.

    Nardini 1540;
    20210408_231429.jpg
    Sculfort with an allen wrench in each place;
    20210408_231824.jpg

    Victor 1440, again with two setscrews plus retard stamping;
    20210408_231940.jpg

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    But back to the adjust true chuck's runout. I haven't had to do this but have wondered about it. Usually the backplate has a boss that fits into the back of the chuck, the edges of the chuck that press over this boss is where the problem lies I think.
    Depending on how bad the runout over distance there is why wouldn't scraping be the correct answer? You should be able to mark which way the kick the chuck back on that side, take the chuck off, and scrape a slight wedge off.
    Assuming it's .0015" higher there make a mark across the back from the rear (When it's laying on it's face with the high side towards you) straight across to the low slide, then two marks @ 45 degrees either side.
    Scrape the first pass between the two 45 degree lines, but leave the rear area alone, then do a markup against a surface plate, then another pass the other direction etc, so by alternating between the surface plate markings for flatness and the markings for effect you eliminate the built in error.
    The last pass would have to be marked against the plate of course.

    If you do your math you should be able to determine beforehand exactly how much you need to scrape away to achieve a true surface. Richard King says each pass is about equal to .0001", every pass alternating direction in normal scraping practice.

    Yes it would be work, but it's the best way I think, and no grinding grit all over every molecule in the shop.

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    Quote Originally Posted by partsproduction View Post
    But back to the adjust true chuck's runout. I haven't had to do this but have wondered about it. Usually the backplate has a boss that fits into the back of the chuck, the edges of the chuck that press over this boss is where the problem lies I think.
    Depending on how bad the runout over distance there is why wouldn't scraping be the correct answer? You should be able to mark which way the kick the chuck back on that side, take the chuck off, and scrape a slight wedge off.
    Assuming it's .0015" higher there make a mark across the back from the rear (When it's laying on it's face with the high side towards you) straight across to the low slide, then two marks @ 45 degrees either side.
    Scrape the first pass between the two 45 degree lines, but leave the rear area alone, then do a markup against a surface plate, then another pass the other direction etc, so by alternating between the surface plate markings for flatness and the markings for effect you eliminate the built in error.
    The last pass would have to be marked against the plate of course.

    If you do your math you should be able to determine beforehand exactly how much you need to scrape away to achieve a true surface. Richard King says each pass is about equal to .0001", every pass alternating direction in normal scraping practice.

    Yes it would be work, but it's the best way I think, and no grinding grit all over every molecule in the shop.
    Yer trying to boil the ocean, "in just one place", though. Adjust/Set true has - or SHOULD have - a lot more adjustment than needs any "scraping".

    If it does NOT have, re-fit it - ON the spindle it runs on - and open it up with a lathe cut. Badly installed is badly installed. Correct that at the source, not the symptom.

    And if the scroll is too badly borked to dial in?

    New parts time. Or new chuck time. Chucks are consumable goods. They HAVE to be.

    No need of any greater magic or tedious f*****g-about than that.

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    I disagree sir, the scroll has little to do with it. Either the body itself is misaligned or by some fluke each jaw is progressively misaligned, which I doubt. It can be checked I suppose by testing with two bars, one 1" X 12" and one 2" X 12, if the error moves around the chuck you are right.
    Every chuck has some, and each individual has his or her threshold for error.

    This is error at the end of a bar not at the front of the chuck, so I can't see how the scroll can be involved.

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    Quote Originally Posted by partsproduction View Post
    I disagree sir, the scroll has little to do with it. Either the body itself is misaligned or by some fluke each jaw is progressively misaligned, which I doubt. It can be checked I suppose by testing with two bars, one 1" X 12" and one 2" X 12, if the error moves around the chuck you are right.
    Every chuck has some, and each individual has his or her threshold for error.

    This is error at the end of a bar not at the front of the chuck, so I can't see how the scroll can be involved.
    Lest we forget "where we came in..." There's more to it than scroll OR back. The jaws move in the body. Either/both of those, too, may be imperfect.

    The OP HAS a "decent" medium-market chuck.

    But "decent" is ALL is is. Bisons are value-for-money, not high-grade, but neither are they all that bad. You only get what you bought, best-case.

    What he is GETTNG is NOT "all that bad". Five thou at 12 inches?
    Most folks would be supporting that with a center, regardless.

    His PROBLEM is he's asking it to act like a SCHUNK!

    Which it was never. Compare their prices. Might want to be sitting down?
    Just checked MSC to name one. Rounded the odd cents.

    With both in 6" forged steel 3-J scroll, manually operated?

    Schunk Rota-S US$ 3,131 against an MSRP of $ 6,162. Nice discount?

    Bison US$ 1,134 against an MSRP of US$ 1,383.

    Schunk, deeply discounted, is STILL close to triple the price of a Bison.

    So "value for money", surely - but ... Schunk don't earn THAT big of a gap without good reason.

    Folks get to wandering about forums and draw the impression that Bison is at the top of the food chain.

    It isn't.

    The big bucks - and the big players - make damned few "manual" chucks at all.
    More than a few simply house-brand Chinese, some those very decent as well, then focus on what THEY are best at. LARGE manual chucks. Power chucks, all sizes.

    Not a lot of CNC or bar machines can spare the cycle-time for manual.
    Not a lot of buyers OF manual ever buy a SECOND one, let alone wear-out "many".

    Power chucks rule the spindle. Else collet. Also power-actuated.
    It's all about the MONEY.

    2CW
    Last edited by thermite; 04-09-2021 at 04:01 AM.

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    Maybe I misunderstood,I took it that the chuck was new or nearly so.

    I may have decided to map the error out and shim the chuck on the surface grinder and grind the back true, total time maybe 1/2 hour, depending on how awake I am that day during the math part.

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    Quote Originally Posted by Hothead View Post
    I have a Vextrax Lathe. it's a good machine. Has all the bells and whistles. The lathe is
    extremely accurate . I have a 6 jaw adjust tru, Bison chuck on it. I would like to grind
    the jaws on this chuck. Reason is with a ground shaft , after indicating in , has about .004
    -.005 run out at 12 " . I did all the instalation of the chuck corectly, took cut on backplate before installing chuck.

    The reason for this post is I have a DRO on this machine and the scale is covering the
    cross slide lock.
    I have a Themac tool post grinder , and i want to lock the cross slide while grinding.
    Anybody have any ideas? I know I could tighten the gib , But thats not right.
    I was thinking of making a lock on the front of cross slide, Attach to where the follow rest is and make something to lock it to the cross slide. Please give me any input on this. OR am i making too big a deal of this.
    Thanks, Ken Livenood
    I would avoid grinding the jaws before eliminating ANY other source of inaccuracy. There can be a few and it's hard to believe Bison made such a f.. up. What spindle nose has this lathe ?

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    My old hobby lathe had a cross slide lock that I used, but I don't believe my 3500lb 14x40 has one. It came with DRO installed so maybe it's under there, but I don't recall seeing it in the manual. The ideas presented are a good way to add one, and I may consider this as a future project if the need arises, but in your case, I don't think you've found an appropriate need, see Orbitals comment.

    Chucks, especially scroll chucks, are not intended to do what you are asking it to do. 0.004"-0.005" run-out at 12" is pretty much to be expected.

    If you want to work on a longish piece with an existing finished OD, holding in only a chuck is not the correct way to do it. You need to hold it with little enough of the chuck to allow bumping in the TS end for support by a center or steady rest. Some people will put a heavy copper wire around the stock in the chuck to allow bumping in the TS end. Better yet, put it between centers, but you may need to use the above to get centers in it accurately.

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    I believe a lot of DRO's are added by the dealers after the lathes are delivered to them, so that would be why you can't see it. Take the taper gib out and shine a light from the back to see, but there may be evidence on the back side of the gib from when it was fitted and tested.
    The Sculfort had no lock or maybe only one, and I don't think the Victor had anything, but that's unusual in my limited experience, plus, if you have a mill adding the hole from the back side for one is a no brainer, perhaps 20% more than what I normally do. No matter either way you have to take the cross slide off. Total time is max one half day.

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    Quote Originally Posted by partsproduction View Post
    .. plus, if you have a mill adding the hole from the back side for one is a no brainer, perhaps 20% more than what I normally do. No matter either way you have to take the cross slide off. Total time is max one half day.
    Even if you do NOT have a mill and must take it to another craftsman with a decent sketch..you get it "right" you do that exactly ONCE for the many-year lifetime of any given lathe.

    CLAMPS were what you had when you didn't OWN the lathes, the company didn't give s**t HOW hard you had to work-around to get the job done so long is it GOT done.. .. and in the course of a single year, one might operate a full DOZEN different lathes.

    MOST had left the factory with right-DECENT locks .. forty years earlier.
    Near-as-dammit ALL were worn TF to useless. It was what it was.

    OWN the lathe?

    "JFDI"

    Classical "no brainer"? Dambetcha it is!

    Loose clamps work.

    They also suck... and cost MONEY.. far more in the wasted time than in the purchase.

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    I like reading the gunsmith stuff, they have some of the same problems I have working hydraulic tubes!
    The jaw chucks have axial run-out, and radial run-out. The 6jaw Bison has adjustment for radial run-out.
    So, if a true test bar is chucked, and dialed in at the front of the jaws, and then the bar tested at 12" out shows run-out, that is axial run-out.
    Looks like there are problems with the mounting of the grinder, I remove the compound, on my small lathes, and fashioned a piece of steel to mount the grinder to, that was helpful, but may not be an option for you.
    The jaws need to be loaded to grind them correctly, there is an easy way to do this on a 6jaw chuck.
    The radius on the jaws gripping surface is close to the same as the through hole on the chuck, so the jaws should be ground as they just protrude in to the chucks center hole. Set the jaws so they just protrude into the hole.
    At the first angle on the sides of the jaws from the gripping face, are Para ell to each other, and square pieces of nylon can be fit in those spaces on the face of the chuck, between the first angle on the jaws.
    The nylon squares perhaps 1\4 to 3\8" in thickness will give a little and load the jaws for grinding, multiple ways to load the jaws, that is one.
    The 6jaws chucks are great, but with wear and use, the jaw contact start dropping out until only 3 jaws are in contact, and the other 3 rattle.
    They do need to be maintained.
    To test jaw contact, I put prussian blue, or regular steel dye that is still a little wet on a ground test bar, and clamp in the chuck, when removed, it will show if all the jaws are contacting.
    The face of the chuck body, should run better then .001 or there is a mounting problem.

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    Gun barrel or hydraulic tube, neither of normal length should be held in just a chuck, 6 jaw or otherwise. There are already better solutions than trying to grind chuck jaws to that level of accuracy.

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    Quote Originally Posted by JCByrd24 View Post
    Gun barrel or hydraulic tube, neither of normal length should be held in just a chuck, 6 jaw or otherwise. There are already better solutions than trying to grind chuck jaws to that level of accuracy.
    Sure, then lets see it! JCByrd24

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    Quote Originally Posted by donie View Post
    I like reading the gunsmith stuff, they have some of the same problems I have working hydraulic tubes!
    One invented nightmare is the same as any other to you. Fabbed from billet boolshit in your hunger for attention.

    Why bother the grownups with your nonsense when EVERY SINGLE TIME OUT you miss something THEY know that you do NOT know... and SHOULD know.. thereby hanging yourself as a poseur as sure as God made little green apples?

    You're an embarassment to the craft!

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    Quote Originally Posted by donie View Post
    Sure, then lets see it! JCByrd24
    Not certain, but at least the oldest of the the several techniques SHOULD be past the 200-years in-use mark? And you are unaware?

    Not a lot of "mystery" left, let alone any "magic" as would be the sole province of any ONE craftsman? And you are unaware?

    Clever play on words, but blowing smoke up other people's arses is not "hydraulics work". Neither is pissing in the collective stewpot. And we ARE aware?

    https://www.practicalmachinist.com/vb/members/donie/

    Read it and grimace. It's BEYOND "weeping".

    So... here's a virtual nickel, kid.

    Go see if you can find some place still sells virtual bubble gum that cheaply, willyah? There's a good lad.

    The rest is above your current pay grade.

    And the grownups have better s**t to do than feed pernicious trolls.


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    Thermite

    Why is it that you have to start trouble with Donie?
    I like to hear what Donie has to say. He has years of experience from running his own shop and working on his 10EE's.

    Hal

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    .004 -.005 does that mean you get +.004 and -.005 12" out?
    and turn the part 180 to get that again?
    guess I would map the error with marking the chuck 12;00 and so on. ...and the pull the chuck and indicate the adjust true to it zero or out.

    If the adjust true dace correction corresponded to fix the chuck error/wobble I would fid that first.
    I have stacked a few rubber bands to hold my compound tight to the screw, but it is not likely to suck in.

    Good to pull the grind infeed when inside the chuck and walk out.

    Be sure the chuck is inspected and cleaned first.

    You can turn the compound to a long angle so the infeed is way less than the dial numbers.
    Last edited by michiganbuck; 04-12-2021 at 06:11 AM.


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