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Old February 17, 2013, 07:21 PM   #1
sig220mw
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Dial caliper off a bit

I have a dial caliper that suddenly now shows to be at .003 instead of zero when completely closed. I understand that the screw below the bezel is supposed to be the adjustment knob to correct it but when I turn it nothing happens. Admittedly I don't know what I am doing since I have never had to adjust it before and have no instructions for it. I have had it for over 10 years and it has the Midway brand but was made in China. Am I missing something or do I just need to get a new one? I have checked it closely for dirt and debris and wiped it down as best as I could so it looks clean at least to me anyway.
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Old February 17, 2013, 07:33 PM   #2
Budweiser
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The screw below the bezel is a set screw, it loosens to allow you to turn the bezel to "zero" and then tighten it to lock it at "zero".
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Old February 17, 2013, 07:36 PM   #3
NESHOOTER
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Quote:
The screw below the bezel is a set screw, it loosens to allow you to turn the bezel to "zero" and then tighten it to lock it at "zero
It's the round clock looking thingy, the pointer stays in place but the dial turns and moves.
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Old February 17, 2013, 08:15 PM   #4
wncchester
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When your 'zero' changes, clean the jaw faces.
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Old February 17, 2013, 11:42 PM   #5
sig220mw
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I have cleaned the jaw faces. When I loosen the bezel set screw nothing happens I can't get the needle to zero. I unscrewed it and then tightened it and nothing changes. I unscrewed it to the point that it came out. Am I doing something wrong? How do you turn the bezel to zero?
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Old February 18, 2013, 12:08 AM   #6
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Turn the dial... Then lock the set screw.
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Old February 18, 2013, 12:12 AM   #7
Mac Sidewinder
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Loosen the screw, grab the outside of the bezel and turn the whole face so that the arrow points to zero. Now tighten up the screw. The set screw only holds the bezel face in position, it doesn't move or change anything.

Mac
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Old February 18, 2013, 01:33 AM   #8
sig220mw
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OK got it. Thanks Smokiniron and Mac. I had no idea the entire thing would rotate. As I said earlier it came with no directions and I've had it for years without any problem until today.
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Old February 18, 2013, 04:05 AM   #9
dacaur
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Keep in mind, that is not the proper way to zero your calipers. To do it properly you really need a 1" standard. Something like this http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32 . Measure the block in your calipers, holding the same pressure you would when measuring normaly, and move the dial to 0.

The big question is, why did it change in the first place?
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Old February 18, 2013, 02:04 PM   #10
smokiniron
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Why did it drift out of adjustment?

Quote:
I've had it for years without any problem until today.
OK.... Here is something to check. On the top flat surface of the caliper there may be two small screws. Those screws apply slight pressure to a brass strip inside the sliding portion of the caliper. In turn, that pressure takes up slack from wear and allows you to keep the jaws of the caliper square to one another - which is critical to accurate measurements.

To adjust: You slide the jaws together, and very slightly tighten the screws to take up and slack. We're talking a few thousandths of an inch at most. DO NOT over-tighten. You can enhance the sliding action with very small amount of lube.. oil works ok.

Now. close the jaws and hold them up to a light. Check for light seepage between the jaws - indicating an out of parallel condition. Adjust the two screws accordingly. Usually, you'll loosen one and tighten the other.

NOW, after all 'play' or looseness is accounted for, THEN you and close the now-parallel jaws and re-adjust the bezel to zero.

Hope this helps!
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Old February 18, 2013, 02:46 PM   #11
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0.003" is a lot of calibration error for dirt to cause AFTER a cleaning. So, there is probably something else going on. Addressing that using the advice already given is a good thing to try.

However, I often find that my calipers are about 0.001" out when closed. I clean the mating surfaces by simply closing them onto a clean piece of ordinary paper and dragging the paper out with the jaws held snuggly closed. So far, that has returned my calipers to zero on the dial without any adjustment of screws. You might also try that to make sure that your cleaning has not left about 0.001" of some sort of surface film.

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Old February 18, 2013, 05:41 PM   #12
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Now that you have the dial at zero. Open and close (a few inches) the calipers a few times. Close them again. If it returns back to zero you are fine. If not shop for a new pair of calipers. If they are "good" calipers like Starett, Etalon then it may be worth it to have them repaired.
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Old February 18, 2013, 07:59 PM   #13
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Good calipers

Mitutoyo... excellent quality and cheaper than Starrett.
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Old February 19, 2013, 12:04 AM   #14
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+1 on that. I use mitutoyo calipers every day at my work (machine shop) Mitutoyo is probably the most common in my shop, followed by starrett then brown and sharp. Ive used brown and sharp, but don't like that they don't have a thumb wheel. "they" say starrett is higher quality, but most don't feel the extra cost is justified for calipers....
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Old February 19, 2013, 07:01 AM   #15
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The Mits can be recalibrated to zero with a paper clip when chips/crud gets on rack. You can carefully wash the rack and blow it out and then take a paper clic in and adjust the pinion so it will zero top dead center again. Get a set of Mit instructions of this from their packaging.
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