Announcement

Collapse
No announcement yet.

D1-4 spindle, should chuck fit flush ?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Forrest, mine was a simpler make one to fit another but i see what you're saying....having two pins, each in contact with both face and cone would allow you to measure across them and the critical dimension can be calculated. Well, now i know how to approach regrinding the lathe spindle if necessary
    .

    Comment


    • #17
      Well this question has been asked many times on a number of forums.

      Rather than to state my opinion, I will refer to two documents.

      The manual for the Jacobs Spindle Nose Collet Chuck states "Place chuck in position on spindle and be certain that you can fit no more than a .004" feeler gauge between the front face of the spindle and the back face of the chuck." They do not want the chuck to fully seat. The mounting instructions want you to tighten the cams while indicating the collet taper to within .0001 inch TIR to allow for high precision centering.

      Compare this with the mounting instructions for Rohm lathe chucks. They state to mount the chuck and without tightening the cams there should be a gap of .0008 - .002 inch. The manual states to evenly tighten the cams. The manual then states "Both the short taper and the face of the chuck must be in full contact with the spindle nose after mounting."


      With the stated tolerance of the mount allowing +.0005 on the spindle, if you mount a perfect backing plate the math shows you will have a .002 inch gap between the back plate and face of the spindle.

      However if your spindle is +.0005 and the back plate is also with in tolerance of -.0005 you will have a .004 inch gap before you tighten the cams. While a .002 inch gap can be closed with normal torque of the cams, you won't be able to close a .004 inch gap.

      While high end lathes and back plates will fit up tight allowing for very quick and highly repeatable mounting, you will also find spindles and back plates that are with in tolerance that will have a gap after tightening the cams.

      You can either live with having to indicate in the chuck each time you want to get it to run very accurate or you can start the process of determining whether your spindle taper, back plate taper or both are out of tolerance and deciding whether you have the skills or money to get the fit you desire.

      I have the opposite problem. My D1-3 spindle is ground undersize. So I have to face or mill the back plates so the two tapers will register...
      Last edited by TriHonu; 12-12-2010, 07:59 PM.

      Comment


      • #18
        Somebody shoot me. A gap at the face is insane, both for accuracy and safety reasons. The whole point of the camlock system is fast, accurate chuck changes. If you had to tweak the cams and indicate a mandrel every time you changed a chuck, you'd pitch it all and go back to a threaded spindle. I can't imagine trying to tweak six cams - good grief! The reason a gap is unsafe is that it subjects the pins to the entirety of the cyclic stress, just like the case of an under-tensioned bolt in which the bolted joint separates. If the gap is closed, a significant fraction of the cyclic stress is shared with the chuck body and spindle nose, greatly enhancing the fatigue resistance of the assembly.

        Jacobs does want the gap to close. You can pull a 0.004" gap shut with the cams. I do it all the time with my 2J Sjogren D1-3, which happens to have a sizeable gap when loose. Sure, you can indicate a collet chuck to get better runout, and tweak the cams a little and bump the chuck with a soft mallet, but it should all happen with the gap closed.

        Comment


        • #19
          The manual for the Jacobs Spindle Nose Collet Chuck states "Place chuck in position on spindle and be certain that you can fit no more than a .004" feeler gauge between the front face of the spindle and the back face of the chuck." They do not want the chuck to fully seat. The mounting instructions want you to tighten the cams while indicating the collet taper to within .0001 inch TIR to allow for high precision centering.
          I don't know that you can infer they don't want the chuck to fully seat from those instructions. they say no more than 4 thou before you've even turned a cam.....Maybe the reason for this instruction is that if the mount is supposed to be a slight interference as Forrest suggest, that technique pulls things snug compensating for any small high spot?

          http://www.neme-s.org/images/Jacobs_...llet_Chuck.pdf

          Originally posted by TriHonu
          Compare this with the mounting instructions for Rohm lathe chucks. They state to mount the chuck and without tightening the cams there should be a gap of .0008 - .002 inch. The manual states to evenly tighten the cams. The manual then states [B]"Both the short taper and the face of the chuck must be in full contact with the spindle nose after mounting."
          my world coincides with Rohms view, both surfaces need to be firmly in contact. The D taper section is so short I can't see it by itself register and hold tooling properly - that if the faces fail to mate, unless you indicated it each time I would suspect that it would end up as a swash plate, with part of the face mating and part not - the taper is the concentric reference but is too short to reliably hold the chuck in proper axial alignment .

          I'm surprised that guys report it the norm for chucks to be some distance from the spindle and that the pins are visible. They've probably seen more lathes than I, but still, its not something i ever remember seeing. I went out and double checked my three and there is no chance of getting a feeler gauge in and no light visible so I believe the faces are firmly in contact as I believe they should be. Frankly it would seem a very un-sturdy mount if it wasn't in contact.
          Last edited by Mcgyver; 12-14-2010, 12:27 PM.
          .

          Comment


          • #20
            Originally posted by TriHonu
            I have the opposite problem. My D1-3 spindle is ground undersize. So I have to face or mill the back plates so the two tapers will register...
            I ended up regrinding the taper and back face on my 10EE. Used a CBN cup wheel on a tool post grinder. I set the taper angle to the compound using an indicator and then ground them. But when you grind down the outer taper you need to grind the face back to make sure the taper mounts to the chuck. Its delicate work. Removing fractions of a thou to get it right.

            Comment


            • #21
              You guys voting for face gap or no gap are missing the point. The A1 and D1 spindle nose taper series is a standard not subject to field revision by stated opinion or exception. Technical changes can be made but the process is exhaustive. Changes are intiated when the comment and suggestion sheet in the back of the standard document is filled out and submitted. The submttal is reviewed by the standards board. From there changes are made only after vetting and comments solicited in a process as stringent as when the standard was originally promulgated.

              I think the face fit-up gap as specified in the A1 and D1 spindle nose series standard is a superb design. Radial clearance on the taper defeats the intent of the spindle nose standard. The standard as written and implemented ensures 0.0001" or better radial and axial registration repeatability of chucks and other workholding tooling resultng in a mechanical connection nearly as rigid as an equivalent mass of solid metal. Thus they can be interchangeably installed on lathe spindles made to the same standard - a portion is shown here in PDF:

              http://www.cushmanindustries.com/cat...menclature.pdf.

              I think this is the correct standard: ANSI Standard B5.9-1967 (reaffirmed 1972) if anyone wants to look it up.
              Last edited by Forrest Addy; 12-13-2010, 01:18 AM.

              Comment


              • #22
                I bought an import chuck that would not mate up completely. The taper portion of the D1-4 adapter plate was just about .0014 too small. I spent some time fixing that. The next import chuck I bought was from Shars. It fit correctly.

                Comment


                • #23
                  I had the same problem.
                  I could not bring myself to grind on any tapers, so I milled out a stack of shims tightly pressed between two 1/4 pieces of aluminum.
                  These fit between the face and chuck back (of course).
                  I had a few each of 0.0005, 0.001, 0.002 and a 0.004" thick.
                  Playing with various configurations I found just the rite combination (0.0025").
                  Been very happy with the results.
                  ( The 4 jaw doesn't need any. )

                  Tom M.

                  Comment


                  • #24
                    Grind? Why grind? I see no reason to grind when the factory that makes this stuff does not grind the chuck mounting plates.

                    If you go too far with the cut of the tapered portion, just take a little off the face.
                    Last edited by Richard-TX; 12-13-2010, 09:39 AM.

                    Comment


                    • #25
                      There is a tolerance on the taper angle built into the standard. The male gauge has diameter-over-pins dimensions for 0.250-in pins located flush with the inner and outer faces of the taper. The tolerances are +/-0.0001". The female gauge taper is to be a "good Prussian blue fit" on the male gauge taper, so it picks up the taper angle tolerance. When fitting the female gauge to a spindle, there is a tolerance on the gap of 0.000" to 0.002" for D1-4. When fitting the male gauge to a chuck or whatever, there is the same +0.002" tolerance on the gap. The male gauge corresponds to the smallest allowable spindle taper. Thus, the minimum allowable gap before tightening the cams is 0.000" and the biggest gap is 0.004", for in-tolerance D1-4 assemblies. In no case is there allowed looseness in the taper fit. The gauges are applied with hand force. There are no provisions for forcing the gauges onto the taper using the cams.

                      Comment


                      • #26
                        When you pay one company $200 for a back plate you expect quality
                        When you pay another company $42 for a back plate you "hope" for quality

                        The 42 dollar guy is counting on your comment tiffie

                        Rich

                        This whole discussion shows why the L Series (ie Lo, Loo) are the finest spindle noses you can have.... in my opinion.
                        Forrest, you are correct with the ANSI Standard B5.9-1967 .
                        They added the DI-3 andDI-4 specs at that time

                        Comment


                        • #27
                          I have a vague recollection of some engineering analyst guy worked out the merits of the A1-D1 series spindle noses Vs the L-x series. Six of one half dozen of the other using gage line dia as a comparison feature for stiffness providing the supporting bearing fit is larger than the gage line dia.

                          However what stuck in my mind is repeat positioning accuracy. Radially, both A1 - D1 and L-x series spindle noses are about the same. The L-x series is axially variable because the taper draws more or less with collar torque, whereas, the A1-D1 series draws up and stops when the flange face mates. The difference is 0.001" or so and 0.0001" or less but them numbers are important only to some people.

                          Adding, some people suggest a "torgue sequence" of the cam-locks A`11 - D1 spindle nose to securing repeatable mounting of their lathe spindle tooling. I submit if the fit-up is clean and blemishes are stoned flush it should make no difference which cam-lock is snugged.

                          And for the record, if Old Tiffie wants to run radial clearance in the taper of his cam-lock equipped lathe that's his privilege. Anyone buying his stuff later should keep his mods in mind. It's a simple matter to face back the spindle nose flat and correct it to incorporate the right amount of draw.
                          Last edited by Forrest Addy; 12-14-2010, 05:11 AM.

                          Comment


                          • #28
                            My 14X40 seems to have a slightly large taper.
                            With 3 chucks ( 4 - 6 - 8") & collect chuck, after snugging #1 a bit I have to indicate the chuck, tweaking each came a smidgen slightly.
                            With a Bison I end up with .001.

                            Grinding this, that or the other 0.0001 is beyond my capability.

                            I seldom change chucks so I can live with it.

                            Comment


                            • #29
                              The manufacture says the chuck should fit flush against the spindle face. I have a 0.004" gap near number 1 jaw. No gap near the 2 and 3. Maybe I should use a breaker bar to try and tighten it just a bit ?

                              Comment


                              • #30
                                Originally posted by TR
                                I have measured. < 0.01mm or very close to zero.
                                TR, are all the pins on the back of the chuck screwed in the same length?
                                Bob
                                Pics of shop and some projects
                                http://s2.photobucket.com/albums/y39...achine%20Shop/

                                Comment

                                Working...
                                X