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  • Chuck run out...

    ... I thought I would check mine.

    First off turned a scrap then put the DTI on it, barely perceptable movement of the needle, so far so good.

    Next test, put a previously turned shaft in the three jaw and put the DTI on that, repeated with some much thinner silver steel. 0.1mm in each case, thats near as dammit 4 thou.

    Is this good, bad or indifferent for a non_Chinese lathe and chuck?

  • #2
    That's not bad, a bit on the far side of good but typical.

    I'd give is a good cleaning and see what that does.
    If it's a cam-loc, try rotating the stud one hole, test and repeat to find the best.

    I helped mine a shade over .001 doing that, then marked a reference.

    Comment


    • #3
      Thanks Ken, that two things I have learned then.

      One, I dont need to worry about chuck run out and...

      Two, like the books say, the 4 jaw chuck is what should be used for accurate work so I just need to get used to setting it up.

      John

      Comment


      • #4
        I don't know what mounting system you have on your chuck, but if it's a threaded spindle, you might want to check the area where the back plate meets the spindle shoulder. I had similar problems and after checking that area found that it wasn't seating squarely on the shoulder. I scraped the back plate to fit 360 degrees and it made a big difference in runout.

        If you are interested, I wrote a post about what I learned and did. http://bbs.homeshopmachinist.net/sho...eadstock+chuck There are a couple of links in the post that lead to some useful information with regard to fitting chucks.
        Last edited by firbikrhd1; 12-11-2010, 02:32 PM.

        Comment


        • #5
          I agree with Firbikr...

          When I first got my logan there was a bunch of 50 year old gunk spooged on the flat annular face that the chuck tightens against. I was getting over 0.001" runout ont he tiny face, which gets magnified with more projection. Some oil and fine steel wool (on low speed) took care of that.

          Was your chuck's back plate machined on your particular lathe? this can take some of the runout out of the chuck itself.

          Mark the high spot of your chuck and then try chucking up some ground stock (like the drill rod) of different diameters. If some diameters are significantly worse than others you probably have a worn scroll and there is not much you can do.

          Like you said though, use the 4 jaw(or collet) for anything needing better accuracy.

          KEJR

          Comment


          • #6
            Thanks for comments.


            It is a D1-4 camlock mounting and I have cleaned the tapers, no gunk on there.

            Comment


            • #7
              I don't know what all of the fuss is about over 3 jaw chucks being exact. I have been doing this stuff for over 20 years. I have never relied on a 3 jaw for accuracy! I learned when I was too young to work in a shop, that if something had to be concentric within 0.010 (0.254 mm) or better, either use an oversize piece of stock and hold it such that you can do all of the turning in one setup and cut it off (using a 3 jaw), or put the four jaw in the lathe and indicate.

              When you examine a 3 jaw, there is so much that can go wrong, it is senseless to expect it to repeat within 0.001 (0.025 mm) every time. Yes, they are a little more accurate when they are new, but that goes away quickly. It only takes a little crud in the scroll, to screw things up severely. If you are too lazy to change to a 4 jaw, then expect to make a lot of practice pieces. Yes there are 3 jaws that are excellent, expect to pay $$$$$$$$ for them. The high end excellent 3 jaws are still no match for a 4 jaw, when it comes to accuracy. Getting good at anything only takes practice. A little patience, and practice, and indicating things in a four jaw chuck becomes second nature!

              Comment


              • #8
                AGO is exactly correct. 0.003" TIR is typical in a three jaw. You can expect a little more or a little less in a new chucks but the 0.003" figure is typical. Three jaw run better if they are cleaned regularly. The gaps where the jaws meet the scroll is a chip magnet.

                Rant alert! Rant alert! Rant alert! Rant alert! Rant alert! Rant alert!

                Rant on:

                A three jaw chuck is not for use on precision concentricity work where a second operation on the opposite end is required. You can start with smooth bar stock and do a beautiful job on the first end but reverse it ine the jaws to machine the other end and the chuck's built in TIR will frustrate you. You can do precision work on a three jaw if you use soft jaws bored in place but the batch count has to justify it.

                Use a four jaw for precision concentricity work. It's made for it. A couple of hours practice and a couple months experience on a four jaw and you'll wonder why you ever bothered with the limitations of a three jaw. Three jaws have their uses and many of them save time and trouble but a three jaw chuck is not a universal solution. I use a three jaw chuck frequently but never where I need second op concentricity.

                You fellows who declare a "three jaw works for me" need to meet the small challenge of learning how and when to use a four jaw. The effort is small but the rewards are huge. You can grip irregularly shaped work and dial in the pertinant features. You can make complex multi-diameter shafts quickly and efficiently where all diameters are concentric. You can grip skinny rings and thin flanges with little deflection and distortion.

                Sure pro machinists and lathe hands use three jaw chucks all the time for some types of work. Using a three jaw chuck for inappropiate work means two things; the uer is a. Too lazy to change it; or b still in training wheel mode.

                In some shops, using a three jaw chuck to grip rough work, heavy stock removal, second op work, delicate work where a four jaw or soft jaws are better employed will make the boss skeptical of your skills and wonder if he made a mistake hiring you. A quick efficiant chuck change followed by a two minute dial indicating job will make him love you, take you home for dinner, and offer you his first born, beauty contest winner, wealthy, generous daughter.
                Last edited by Forrest Addy; 12-11-2010, 06:16 PM.

                Comment


                • #9
                  Originally posted by The Artful Bodger
                  ... I thought I would check mine.

                  First off turned a scrap then put the DTI on it, barely perceptable movement of the needle, so far so good.

                  Next test, put a previously turned shaft in the three jaw and put the DTI on that, repeated with some much thinner silver steel. 0.1mm in each case, thats near as dammit 4 thou.

                  Is this good, bad or indifferent for a non_Chinese lathe and chuck?

                  That's neither good, nor bad. It's just the nature of a three jaw chuck. (I presume you mean a three jaw chuck).

                  The chuck could be off quite a bit, say .008" (Approx. 0.2 mm to you). Turn something. Then take it out and put it back in a different location and you will see the error. They all do that to a greater or lesser extent. Not an issue.

                  Even if you start in a perfectly zeroed 4 jaw chuck and then put it in your three jaw (you may have done that - you didn't say if the first chuck was a 4 jaw), you will get the same variation. Three jaws all have runout, some more than others.

                  My 2 cents.

                  EDIT: What Forrect said! (Except the part about the first-born daughter. )

                  Comment


                  • #10
                    Thanks everyone, my bit of reading has been confirmed by what you all have written about the 3 jaw 4 jaw chucks.

                    I have seen a lot posted about truing 3 jaw chucks etc so I thought, more for curiosity than anything else, I would try mine. I am quite happy with what I have, except, why on a 12x36 lathe do they have to supply a 4 jaw chuck that I can hardly lift? I guess thats another reason to put the 3 jaw carefully on the shelf and use the 4 jaw all the time for chuck work!

                    There has to be something a bit more convenient that mounting the DTI on the cross slide and phutzing around getting it on centre..(I feel a project coming on!)

                    Comment


                    • #11
                      Originally posted by The Artful Bodger
                      Thanks everyone, my bit of reading has been confirmed by what you all have written about the 3 jaw 4 jaw chucks.

                      I have seen a lot posted about truing 3 jaw chucks etc so I thought, more for curiosity than anything else, I would try mine. I am quite happy with what I have, except, why on a 12x36 lathe do they have to supply a 4 jaw chuck that I can hardly lift? I guess thats another reason to put the 3 jaw carefully on the shelf and use the 4 jaw all the time for chuck work!

                      There has to be something a bit more convenient that mounting the DTI on the cross slide and phutzing around getting it on centre..(I feel a project coming on!)

                      Yes, those 4 jaw chucks are heavy! I prefer the three jaw for it's quickness. but if you are good at centering a 4 jaw, just leave it on all of the time.

                      Comment


                      • #12
                        I could never center a 4 jaw chuck without a lot of fussing around with the chuck .

                        I watched this video, and immediately made a baby chuck key. I can center work quick and easy now.
                        http://www.youtube.com/watch?v=2KMhx4DbyDg

                        Comment


                        • #13
                          Run-out and weight etc.

                          Originally posted by The Artful Bodger
                          Thanks everyone, my bit of reading has been confirmed by what you all have written about the 3 jaw 4 jaw chucks.

                          I have seen a lot posted about truing 3 jaw chucks etc so I thought, more for curiosity than anything else, I would try mine. I am quite happy with what I have, except, why on a 12x36 lathe do they have to supply a 4 jaw chuck that I can hardly lift? I guess thats another reason to put the 3 jaw carefully on the shelf and use the 4 jaw all the time for chuck work!

                          There has to be something a bit more convenient that mounting the DTI on the cross slide and phutzing around getting it on centre..(I feel a project coming on!)
                          Well AB you have discovered that not only are bigger chucks heavier but they are very awkward to lift and maneuverer on and off and into place as well.

                          Nothing new there - except that it a classic OH&S set-piece for a nasty accident or a badly damaged back - the more so as we get older.

                          It is the main reason - as we get older among others - that large chucks are left on the lathe or off and why a lot of larger vises and rotary tables and dividing heads are either left on the mill table or left off it all together.

                          That is the main reason I limited my lathe to 6" chucks (mine are about 5"), my mill vise to 4" (I use a matched pair or precision tool-makers vises if I want to camp anything longer) - otherwise it gets clamped to the table. I pretty well always use my 6" rotary tables and my 8" unit stays under the bench unless it is really needed - and that it where the hydraulic lifting table comes into it own.

                          Leaving a 4-jaw chuck permanently on the lathe is not a good idea if you need to use a face-plate or collets - or a 3-jaw chuck.

                          Here are the common specs for a 3-jaw chuck. Note that there are two kinds of "run-out":
                          1). parallel - where the axis of test piece is parallel to but not co-axial with the head-stock spindle axis; and

                          2). conical - where the axis of the test piece is not parallel to the head-stock spindle axis.

                          Either both or just one can be present.





                          Here are the normal specs for a 4-jaw chuck:





                          Note that while there is no "conical run-out" spec. there is no reason to believe that it is not or cannot be there.

                          While a 4-jaw chuck is very good at adjusting for minimal Total Indicated Run-out (TIR) on one spot on the job or test piece it is not at all uncommon for the test piece or job to have a conical run-out else-where.

                          The four-jaw chuck is excellent for holding irregularly-shaped or non-round parts or for holding round parts eccentrically.

                          I have about 0.003>0.005" clearance between the flange on my lathe and its mating bores on my back-plates. I can set the 3-jaw - or my collets - to very close limits of TIR for a particular size or job - about 3 minutes maximum - though I rarely have to.

                          So, I do a lot of chuck changes on my 10" lathe and it is quite easy to do without undue risk or strain.

                          Sometimes bigger machines and tools cause as many or more problems than they save or cure.

                          If I had your problem/s with changing chucks I'd put a lifting eye in the chuck and lift etc. with a hoist. Remove the lifting eye and replace it with a screwed plug during machining.

                          There is no good reason why mostly larger machine vises, rotary tables and dividing-heads should not have lifting eyes and be lifted and lowered by a hoist either.

                          Comment


                          • #14
                            Controlled lifting

                            For heavier lifts I use my engine hoist and/or my hydraulic table.

                            The engine hoist has an air-over-hydraulic control which saves pumping by hand to lift and which gives me very fine remote control during lifting (it has to be lowered as normal by hand by off-seating a hydraulic valve).
                            https://www.machineryhouse.com.au/Pr...stockCode=A351

                            The hydraulic table has a good lift height (780mm ~ 30.7") and a good lifting capacity (500Kg ~ 0.5 "long" ton) and is very easily controlled and maneuverable.
                            https://www.machineryhouse.com.au/Pr...stockCode=J050

                            I also have an excellent USA-made "Pullzall" electric hoist with a 450Kg (~ 1,000 pounds) pull/lower capacity:
                            http://www.pullzall.com.au/default.a...article&ID=106

                            http://www.pullzall.com.au/default.a...rt=asc&limit=0

                            I am going to modify my engine hoist and fit the Pullzall to the back of the vertical column, a pulley/sheave to the top of the column and another sheave to the "hook" end of the crane lifting jib/arm. I can leave the hoist arm at whatever height I want it and use the Pullzall to raise/lower the load/chuck. I may another sheave on the hook end of the lifting arm/jib to give me half speed but better torque and control at the hook end (ie with the mill vise or the 8" rotary table or lathe chucks etc.).

                            As all of my machines are under 0.5 ton (~ 1120 pounds) moving stuff is a lot less of a problem than it might otherwise be. Access within my shop is pretty good and if stuff needs to me moved for access to something else its not much of a problem.

                            My MIG welder, 20 T press, shaper, oxy-acet set are all on castors and can be moved easily as they are often used out on the carp-port concrete apron.

                            I have four of these benches (which I re-inforced ie stiffened and braced as well as new central steel legs) which provide support for my lathe,smaller mills and grinders as well as excellent shelf and draw storage but only weigh about 100Kg (~ 220 pounds).

                            https://www.machineryhouse.com.au/Pr...stockCode=A380

                            I learned some very good lessons in my time and promised myself that as many as possible would be incorporated into my new HSM shop so as to reduce the chance of accidents as I grow older.

                            Lifting chucks, vises and rotary tables etc. very much included.

                            Comment


                            • #15
                              Soft jaws

                              Realistically, the cheapest, easiest, fastest and most accurate way to hold a job in a lathe is to use cheap (aluminium or mild steel are excellent) soft chuck jaws. They can be made from anything that will do the job in the scrap bin.

                              The bored hole will be as true and concentric as the lathe head-stock spindle and if faced-off will be as straight and true as your cross-slide.

                              Their repeatability is excellent and they have none of the "draw-in" problems that collets have.

                              https://www.machineryhouse.com.au/Se...mageField.y=15

                              https://www.machineryhouse.com.au/Se...mageField.y=15

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