Help with setting zero on a micrometer

  1. Dcal Member

    Messages:
    1,409
    Location:
    Antrim Northern Ireland
    I have acquired a 0 to 25mm micrometer.
    It's in excellent condition but the zero mark does not line up with the scale on the micrometer.
    I can rotate and lock the scale so that the scale lines up with the datum line, but then it undershoots the zero mark by 0.2mm.

    IMG_9619.JPG

    If I measure a 0.2 feeler gauge, it all lines up perfectly and I can see the zero mark.

    IMG_9609.JPG

    If it overshot by the same amount it might be easier to live with but I struggle to remember if it 0.2 over or under.

    IMG_9614.JPG



    Is this normal?
    Should I just learn to live with it?

    Can the anvil be adjusted to sort it (I can't see any way to adjust the anvil)
    Or can I adjust the position of the screw thread to adjust it?
    Or should I take 0.2mm from the barrel where the scale seats in the C frame.
    Or is there another fix?

    Thanks
     
  2. mpats

    mpats Forum Supporter

    Messages:
    1,031
    Aberdeen
    Can you see a small hole in the barrel (the bit with the graduations on it)? If so, using the small pin spanner that should have been in the box you can turn the scale so it lines up, thus making it zero at zero.
     
  3. RobCox

    RobCox Member

    Messages:
    46
    Location:
    Cambridge, UK
    You can adjust where it lines up at zero. I think the little hole at the base of the ratchet enables that mechanism to be removed and the barrel with the graduations unscrews from the polished rod. It looks like someones had it apart and not lined it up properly when it was put back together.

    There are some videos on Youtube showing how to adjust them. I think Doubleboost might have posted one a while back.

    Rob
     
    Dcal and eLuSiVeMiTe like this.
  4. Dcal Member

    Messages:
    1,409
    Location:
    Antrim Northern Ireland
    I can adjust the scale to to line up the zero, but I can't see the zero graduation (or any of the other marks that relate to the measurement.)
    See first photo, the scale is covered by the sleeve so I can't see the marks.

    Is there a way to move the scale, or the sleeve, or the anvil to sort this?
     
  5. eLuSiVeMiTe

    eLuSiVeMiTe Forum Supporter

    Messages:
    9,690
    Location:
    Bedfordshire England
     
    Dcal likes this.
  6. Wallace

    Wallace Member

    Messages:
    6,574
    Location:
    Staines, Middlesex, England.
    It has either been set incorrectly at some stage or dropped on the anvil. Have a look for chipped paint and damage on the end and check that the faces line up correctly, in the first photo they do not appear to but that could be the camera angle.
     
    Dcal and Parm like this.
  7. Dcal Member

    Messages:
    1,409
    Location:
    Antrim Northern Ireland
    Thanks for all the replies.
    I don't think I'm explaining the issue at all well, but I think @Wallace might be closest to the mark.
    I can't see any damage and the anvil and spindle faces seem to line up perfectly.
    This might have been wrong from new.

    This is part of a set, first two photos below are of the 0 to 25 measuring a 25mm test piece.
    The third is of the 25 to 50 measuring the same 25mm test piece.

    The 25 to 50 lines up perfectly with the 25mm graduation, the 0 to 25 not so much and I think it is between 0.2 and 0.3 mm shy of the mark.
    Both had the zero point adjusted

    IMG_9628.JPG
    IMG_9632.JPG
    IMG_9627.JPG
     
  8. Agroshield Member

    Messages:
    186
    As you say, the barrel needs to go 0.2mm to the right to make the graduations line up. If you can remove the barrel, then maybe you can put in a 0.2mm spacer washer (use a piece punched out of a feeler gauge) between it and where it seats onto the shaft.

    As a very last resort, remove the barrel and sand off a little of the left hand end of it until the graduation is exposed beneath it.
     
    Dcal likes this.
  9. JulieandTony Member

    Messages:
    149
    Scotland
    Robcox has it spot on, remove the end ratchet then the outside barrel can be removed, it is on a small taper, the actual inner measuring rod can be screwed in or out, and usually an outer ring can be adjusted , by adjusting these, you can set it to be both in-line (rotary) with the zero line, and match the end of the barrel with the zero mark.

    Often there is another ring than tightens on the thread of the measuring rod, this allows you to adjust how stiff it is to rotate.
     
    Dcal and Gragson like this.
  10. JulieandTony Member

    Messages:
    149
    Scotland
    So I have just stripped one down to show you , hopefully the photo uploads, yours will be slightly different - metric for a start !

    Notice I unscrewed the ratchet, then the barrel comes off, on the main part you can see a split ring nut at the far right, turning this out will shift the barrel to the right so you can align the end of the barrel with the zero mark, by fitting the barrel in the right rotational alignment, you match the zero on the barrel to the zero line.

    It takes several attempts!

    The ring with the hole, a little to the left of the ring described above will adjust the stiffness of the threads.
    DSC_0469.JPG
     
  11. JulieandTony Member

    Messages:
    149
    Scotland
    Like this
    DSC_0470.JPG
     
    Turbo, RobCox, Gragson and 1 other person like this.
  12. Dcal Member

    Messages:
    1,409
    Location:
    Antrim Northern Ireland
    Well I went for @Agroshield last resort in the end.

    Following @JulieandTony instructions I took it apart.
    It is slightly different to the Moore and Wright one he kindly took apart for me and I can't see a way of adjusting the measuring rod or the position of the barrel other than adding a small shim (which would make the problem worse in my case) or sand 0.2mm off the barrel where it seats into the C frame, which is what I went for.

    IMG_9601.JPG
    IMG_9602.JPG

    Just below the ratchet there is a slot but I can't see a thread. It wouldn't budge when I tried to unscrew it and I didn't want to force it and make a mess.

    Instead I used a sheet of glass and a few grades of sandpaper to sand the 0.2mm of material off the end of the sleeve.
    I kept rotating the sleeve and used different patterns to try and keep it all square.

    IMG_9653.JPG

    IMG_9658.JPG

    It took a few goes and was surprisingly difficult to remove the material but I've now got a micrometer that I think works as intended.

    IMG_9660.JPG

    Photo below is measuring the 25mm test piece, I didn't have a sharp photo of the whole micrometer.

    IMG_9663.JPG
    I could maybe have sanded another 0.05 off it but I'll not push my luck and call it good to go.

    Thanks again for all your help
     
Advertisements