Announcement

Collapse
No announcement yet.

Headstock spindle freeplay?

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

  • Headstock spindle freeplay?

    I am not sure this is right but here is my issue:

    I have a Craftex B2227L 10x18 Lathe. I always had surface roughness issues. This morning while taking some reading on the dial indicator I noticed when rotating the chuck the indicator was moving past the index then back to index point.

    I started pushing and pulling on the chuck and I get approx 0.004'' of play when doing so.

    I chucked a piece of Ground stock and started making checks. The chuck runout is approx 0.003''. If I pushed lightly I get approx 0.002 to 0.003'' of deflection same if I pull. If I push really hard I get approx 0.004 to 0.005''.

    This appears to be big numbers, I don't know If I can adjust the spindle or not.

    I appreciate all comment.

    Cheers
    GST

  • #2
    Yes, for a spindle those are really big numbers. I'm not familiar with the Craftex, but... many smaller lathes adjust preload of the bearings by a nut at the left end of the spindle. It's usually secured with a collar or similar. if so...adjust carefully until you feel some rotational resistance (on an Emco, you spin the 5 inch chuck rapidly by hand until it only turns 1 revolution - very subjective!) then test run at 1000 rpm for 20 minutes making sure the front bearings do not get more than "warm" (say 140F). YMMV.

    And.. to get past chuck runout and other related issues, ideally you should do your test at the spindle nose - not with the chuck installed. A test bar set for the native MT of your spindle is the usual way. Be aware that any test bar will bend.

    And of course, call Craftex for their proceedure..
    Last edited by lakeside53; 11-28-2012, 02:06 PM.

    Comment


    • #3
      Yes I did contact Craftex, I am waiting for their lathe expert to call me back. I will check the headstock for this adjustment.

      GST

      Comment


      • #4
        STOP!. How large was the material? How far did it stick out to the indicator contact? What chuck did you use to hold tte work? How deep was the work engaged? All these are interdependant variables. The important thing is the deflection went back to zero as soon as the force was removed.

        Here's a lesson for all learners and noobs. Blame the machine and the spindle LAST. Just because you may not have a world of experienmce doesn't mean anything inexplicable can be blamed on anything "not-you" I've been around and in machine tools for 50 years and even now I have to have the results of three or more non-cutting tests in front of me before I consider faults in alignment or spindle bearings.

        Finish problems how? What kind of finish problems? Same problems with all tools or just a few?

        Single phase induction motors run like one cylinder gas engines. If you're having problems with finish and your machinre is driven with a single phase induction motor, I'd first isolate the motor from the machine to the extent possible and drive it with a loose belt taking light cuts. Try a few cutting tests and see if thgere is any improvement in sinish. .

        Comment


        • #5
          I do understand your concerns. I had surface finish problem with most of the pieces I was turning. Even with Live centre or Steady rest. I am aware of the single phase motor causing vibration, and I do have that problem.

          I was mostly concern by the deflection of the chuck under light loads. Nothing heavy, just turning the chuck manually create a deflection.

          I talked to the service rep this afternoon and the lathe needs to be readjusted after break-in, which is not in the manual. It has tapered roller bearing and they need to be retightenend. They are trying to find the torque specs for me.

          I'll let you know if this fix my problem.

          GST

          Comment


          • #6
            You might also consider that the chuck might not be on correctly.
            the tinyest bit of dirt could prevent it seating properly and would flex under load.

            Also note that even with my 1000lb lathe, I can measure 'deflection' by yarding on it.
            The whole *lathe* twists and bends with amazingly little force when your talking about 0.001"
            Think about it, if it bends 0.001" at 10lbs, that means at 10,000lbs it would bend 1 inch. I wouldn't be suprised at all if my lathe bent 1" if a semi truck ran over it, so I shouldn't be suprised 10lbs would bend it 0.001".

            Repeat after me: Metal is as rigid as a wet noodle.
            The sooner you make that your motto, the sooner you will figure out just why everything is bending and flexing on you and why nothing you turn is 'straight' and without taper.

            As far as surface finish.. Well, First off give up trying to get a good finish on 'mild steel' or 'mystery steel'. You might be able to do it some days, then the very next pass it will be ulgy as sin.

            Consider trying on aluminum you buy from the metal store. Those alloys typicaly give *wonderful* mirror like finishes with little effort and will help show you more if its the lathe or not.

            (mild steel on the other hand is often sanded and polished just to get something that does not look god awful)
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

            Comment


            • #7
              Thanks Black_moon.

              I am probably expecting too much of my equipment. It is not bad overall and I am working all the bugs out slowly.

              I am mostly turning 6061 and 7075. As expected, the 7075 gives a better surface finish than the 6061, but nothing a lightsanding and polishing won't take care.

              Cheers
              GST

              Comment


              • #8
                With my 10" atlas I can put and indicator on the chuck and make it move by pushing pretty much anywhere on the lathe. Seriously, I can push and pull on the tailstock and make the indicator move, push down on the center of the bed, push on the headstock itself, anywhere.

                Not sure how thick and solid your lathe is, just pointing out that smaller lathes aren't very rigid.
                Andy

                Comment


                • #9
                  OP : wet noodle lathe or not... you still shouldn't get 3 thou of movement at the chuck with a "light" push. How can you turn anything with typical tool pressure? You sure as heck should be able to get a quality finish on 6061/7075 without polishing etc. Preload issues often show up as repeating patterns.

                  Try to isolate what may be spindle preload and and what is just "lathe flexing" - including loose gibs on the compound and cross slde, and apron not tied down correctly. I had an Emco V10P that gave me fits with finish. That turned out to be a simple preload. Same with my 4000lb Polish 14x40. For some reason guys think they can run them for 40 years and never check /adjust anything
                  Last edited by lakeside53; 11-29-2012, 12:36 PM.

                  Comment


                  • #10
                    Well I checked everything and Andy you are right I can make that chuck move by pushing on the tailstock or the headstock.

                    I rechecked the mounting bolt and 1 was loose, I retighten and it made things a lot better, I still get deflection but about 1-2 thou now.

                    I'll try stiffening my table with crossmembers and check everyting else, maybe I missed something.

                    GST

                    Comment

                    Working...
                    X