Announcement

Collapse
No announcement yet.

Lufkin 680 Inside mic adjustment

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

  • Lufkin 680 Inside mic adjustment

    Google search didn't come up with an answer. I have my father's Lufkin 680 inside mic set. Went to use it and the mic barrel is pretty hard to turn, but smooth. No way to get an accurate measurement with the amount of force required. There is no friction clutch. It's clean but obviously gummed up a little. I think it was about .001" off zero as well. I've shot Starret M1 lube into it with no effect. There is no external adjustment or accommodation for a spanner. There is a screw on the end of the spindle but loosening or removing it so far has had no effect. I don't want to force it and I'm afraid to unwind it all the way until I understand how it works. Looking for some guidance before I do something I shouldn't.
    Attached Files

  • #2
    You do not want an inside tube/rod micrometer head to move easily or the thimble will rotate when measuring in places where you can not hold it.
    A friction thimble is unusable inside a bore where hands will not reach.

    Comment


    • #3
      Well, there is easy and then then not so easy. I unwind the end rods before I can get the spindle to move. So it's supposed to be a bit tight, fine. Shouldn't the zero be adjustable somehow with that screw on the end of the thimble?

      Comment


      • #4
        This is a Mitutoyo rod mic that I bought new about 2 years ago, had time while parts were running today so I took it apart.
        There is no tension control for the threads, there are 2 set screws that hold a short rod in the thimble end which are used to set it.

        One of todays jobs, 6 of these parts made an absolute mess of 954 Bronze chips in the machine, one of the good things about an enclosed machine with flood coolant is that you can hose down the chips with a coolant hose. Like an old guy hosing down his sidewalk (-:

        Comment


        • #5
          An inside micrometer head can be quite tight and cause no issues, as using an inside mic doesn't involve feel on the thimble rotation like an outside mic. For an inside mic you set the size close and move the mic around getting a feel for the smallest point. Keep adjusting until you have a good feel where the mic will pass through but still have a small amount of drag when it does.

          Comment


          • #6
            Don't clean it too good , you want the drag.
            I got a new in box Moore and Wright. It was stiff, so I overcleaned it, went too easy.
            they seem to stiffen up if they sit a long time..

            Comment


            • #7
              Gzig5 , I have that model also. If you unscrew the barrel all the way you will see what looks like a small flange with knurled on it. That knurled is for adjusting the drag. The knurled is tight, you just ha e to turn it a very small amount to to feel a difference . John b.
              John b. SW Chicago burbs.

              Comment


              • #8
                If it's anything like the starrett micrometers the barrel is held on with a taper. Put that small screw back in, but leave it about a half a turn loose and smack it with a plastic or other soft faced hammer. That should release the barrel from the taper on the micrometer screw. Do it with the micrometer screw locked at a known measurement and then reinstall the barrel onto the taper with the numbers lined up correct for that measurement.

                Comment

                Working...
                X