Announcement

Collapse
No announcement yet.

A tale of two Starrett 199 precision levels

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

  • A tale of two Starrett 199 precision levels

    I discovered sometime ago that my Starrett 199's don't indicate the same even though both are calibrated correctly when swapped end for end on a surface plate with locating stops.

    One reads level and the other reads one mark off level. Granted one mark is 0.0005" in 12" so not terribly off but these are precision levels and should read the same, or should they? Is one line off level acceptable as long as the calibration is correct and how do I figure out which level is correct. I leveled my surface plate with the one that currently shows level but maybe the one that shows one mark off level is correct.

    I haven't spotted either one yet but my initial gut feel is they are pretty flat as finger pressure on the corners and centers shows no movement of the bubble.

    So is there a trick to determine which is correct? I don't have any other precision levels or metrology instruments at my disposal.

    Ron

  • #2
    A level can be (must be) adjusted to read right. If one repeats the same reading when reversed, it is correct. Set the other one to match it.

    If they both repeat correctly when reversed, then I am not sure what the question is..... Are you saying they repeat when reversed, but then they also do not indicate on the same line? That they both repeat, but not at the same place?
    Last edited by J Tiers; 12-13-2017, 07:47 PM.
    1601

    Keep eye on ball.
    Hashim Khan

    Comment


    • #3
      Levels are self testing--You don't need any other equipment. But you do need clean surfaces. You're into the dust spec and oil film error range.

      Comment


      • #4
        Originally posted by J Tiers View Post
        A level can be (must be) adjusted to read right. If one repeats the same reading when reversed, it is correct. Set the other one to match it.

        If they both repeat correctly when reversed, then I am not sure what the question is..... Are you saying they repeat when reversed, but then they also do not indicate on the same line? That they both repeat, but not at the same place?
        Jerry,

        They both repeat when swapped end for end but do not read the same. One reads level and the other reads one mark off level. They both are placed in the same spot with the help of stops and the base of each level and surface plate is clean.

        Comment


        • #5
          Originally posted by CCWKen View Post
          Levels are self testing--You don't need any other equipment. But you do need clean surfaces. You're into the dust spec and oil film error range.
          Ken,

          I thought the same thing but after several cleaning sessions with no change it must be something else. I bought these off Ebay so it could be that one or both have been refurbished at some point. But the real question is how can I tell which one is correct. My wife tells me I have a bit of OCD and she may be right because the fact that two precision levels reading differently yet calibrated correctly, just doesn't set well with me.

          Comment


          • #6
            Sounds to me like both levels are off by a smidge and your surface plate is too since it was leveled with one of them. Use both levels to re level the plate. The correct reading will be the split between both levels. Once the plate is true, use it to set both instruments to zero.
            Last edited by Dave C; 12-13-2017, 09:04 PM.
            “I know lots of people who are educated far beyond their intelligence”

            Lewis Grizzard

            Comment


            • #7
              I think what you are suggesting is impossible. Identical levels calibrated in the same spot must provide identical readings. Here's my theory, your
              levels are not identical. One of them is more sensitive. Both are correct, but one is not sensitive enough to register the tiny amount of tilt of
              your surface plate.

              Comment


              • #8
                Either what RichR said about being different, or they are actually irregular, or another possibility.....

                See if you can rig up an arrangement to deliberately TILT the levels enough to move by one division. A screw adjustment, or a longer smooth piece tilted with shim stock.

                Set with one of them to be off one more line. then check with the second. Do this for each line on the first level. record and report the results.

                Either they will move different amounts, OR one will not move a consistent amount, more at one setting and less at another (vial not ground right).

                Also possible is that the high spot on the level is not in the middle on one.... not where the lines show.
                1601

                Keep eye on ball.
                Hashim Khan

                Comment


                • #9
                  Clearly this is stressing you, so you should send me one of them, and your problem will be solved.

                  Comment


                  • #10
                    Originally posted by nc5a View Post
                    Jerry,

                    They both repeat when swapped end for end but do not read the same. One reads level and the other reads one mark off level. They both are placed in the same spot with the help of stops and the base of each level and surface plate is clean.
                    If one reads one mark off when swapped end for end, it is not adjusted correctly. I'm still not clear by your description though. Mark the high side of the level with a piece of tape. rotate it 180 degrees. Does the bubble follow the tape or move to the opposite side?

                    Comment


                    • #11
                      I took it that reads at the SAME MARK when turned around.
                      1601

                      Keep eye on ball.
                      Hashim Khan

                      Comment


                      • #12
                        am I overlooking something. Set both sights to level a or b level and they are both set. You just have one sight off.The bubble will always be level. Hence the name.

                        Then check your table and level it accordingly. JR
                        My old yahoo group. Bridgeport Mill Group

                        https://groups.yahoo.com/neo/groups/...port_mill/info

                        Comment


                        • #13
                          I wonder if a bruise or some easily over looked raised metal is affecting interchangeable readings. Have you glided a stone over the reference surface while being acutely aware of sensations in your fingers signalling catches on microscopic burrs and other proud metal defects?

                          Have you blued your levels to your surface plate (note: most master precision grade levels are deliberately scraped or ground with a 0.0005 concave to ensure end bearing when placed on a flat surface.)

                          Comment


                          • #14
                            A level is only as good as it's vial. That seems to be a key piece of information missing in many of the responses. Imperfections on the inside the vial, improper shape of the vial or improper marking can all make the bubble appear to be level when it is not or vice-versa.

                            A vial from a cheaper level will not make a suitable replacement for a 199. I see guys make this mistake more often than not - I've even seen guys who insist on using cheap plastic levels with acrylic vials for leveling machines. They've heard that levels are self-calibrating and have checked their cheap plastic level and believe that means it has the same sensitivity as a master grade level.

                            Let me reiterate: a master precision level provides accuracy and precision because of two reasons - the precision housing AND the precision ground vial. A bad vial makes for a bad level.

                            Comment


                            • #15
                              Suppose the whitworth principle applies, you need a third, then you can compare them all like straightness etc
                              Mark

                              Comment

                              Working...
                              X