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  1. #1
    Mazatroll is offline Plastic
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    Default Which are more accurate, dial or digital calipers?

    In the same price range from reputable co's. Also I would appreciate opinions of the B&S Shop Cal (6" digital). It is very reasonably priced and Swiss made.

  2. #2
    Ox's Avatar
    Ox
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    I kant imagine that a caliper is eny more accurate than the dial can measure. Just b/c the resolution is finer - doesn't make it more accurate.


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  3. #3
    beege's Avatar
    beege is offline Hot Rolled
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    I was told that digital indicators were more accurate than dials...

  4. #4
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    dandrummerman21 is offline Cast Iron
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    i think that it is all about how u use the calipers and the age and condition of the dial calipers
    at my work, there are many of the shops dial calipers that i would never use, because they are inconsistant. most dont measure gage blocks right
    i have 2 mitutoyo digitals that measure way better than any of the forementioned dial calipers

    now my supervisor has 8 inch dial calipers that i do trust. he has "inspection use only" written on the box and he only uses it in more precise applications where a micrometer cannot be utilized.

    i guess it is all about the individual tool

    btw my supervisor has an older version of the shop cal, and it is great. i like the round depth measuring bar.

  5. #5
    J_R_Thiele is offline Hot Rolled
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    From what I have read- neither.

    It is the vernier caliper which is most accurate across its range. It has no cummulative error, and few other ways error can be introduced- if you know how to read one.

    With the dial and digital caliper you have a mechanical or electrical system which translates the scale to something you can see and interpret. With the vernier system- it is YOU who translate the scale.

    Having said all that- I use all three. If I am really concerned-I use a mike.

    I have a B&S Swiss make caliper and like it- especially if I am working in both metric and imperial. With the digital you must be very careful about where you set your zero- as you can set it anyplace on the scale- and I do. If I have a part I want to turn on the late to 28.5 mm I would zero the scale at "true zero", then open them to 28.5 mm and reset the zero for a "relative zero". I would then switch the scale to imperial, measure the part- and the reading is what I need to remove using my imperial scale lathe. The main disadvantage is that you can only read to .0005

    If I had to have only one type- and no micrometers- I would use a dial indicator and guage blocks. If you want 2.456 -use the guage blocks to stack up as close as you can- adjust the dial to your guage blocks, then remeasure until -You- are consistent, and then make your readings. You would be suprised how well this can be make to work if needed

    Some of the above seems like heresy to be posting on a metrology forum- but you can get a set of guage blocks and a good quality dial caliper for much less than a set of quality micrometers. To me it seems better to use what you have or can afford than to not aspire to more accuracy for lack of finances.

  6. #6
    apestate is offline Stainless
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    Digital will be more accurate in that scenario.

    Dial calipers are off by .001" for about 25% of the needle revolution. If you want to check this, check a pin set every .010 for .100 of range, no cheating.

    95% of dial calipers have this error. Digital calipers do not.

  7. #7
    Perry Harrington is offline Titanium
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    Default

    They all have their uses. A set of Mike standards will assist you in determining the relative accuracy. I have vernier calipers in 8", 12", and 24" sizes, with dial calipers in 6" and 12" sizes. I have a few digital calipers too. I have a few digitals that I bought at Kragen's when they had a sale on them. These are used for everyday BS around the shop. No love loss if they get messed up, just toss em. I have verified them to be accurate to .0015 over 6 inches. I have a Mitutoyo digital caliper that was tested against the same Mitutoyo Mike standards, and it showed zero error over 6 inches. You get what you pay for.

    When I'm measuring a shallow shoulder (usually less than 1/4") I will break out 2 vernier calipers and take measurements with them, and possible a dial caliper, so I have an easy, plainly read basis to read the other tools (avoids the tired eye problem with verniers). I will take multiple measurements with the "feel" I want and verify them. If I'm realy picky I'll stack some gage blocks and compare to them. My experience has shown that I can hit tolerance with this method, and it helps eliminate errors from damaged inspection tools.

    If you don't have a set of vernier calipers, you need to get some. You can never be certain that your dial or digital calipers aren't lying to you, because they may read the truth in one spot and not in another.

  8. #8
    dandrummerman21's Avatar
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    Quote Originally Posted by J_R_Thiele View Post
    If I had to have only one type- and no micrometers- I would use a dial indicator and guage blocks. If you want 2.456 -use the guage blocks to stack up as close as you can- adjust the dial to your guage blocks, then remeasure until -You- are consistent, and then make your readings. You would be suprised how well this can be make to work if needed
    wow that is a great idea.
    never thought of that before

  9. #9
    Metrologist is offline Plastic
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    As an old metrologist (emphasis on the old !) I give my vote to the Vernier caliper, then the Digital and the Dial last.
    However I use a couple of Dial Calipers almost all the time in the home workshop but I do check them frequently.

    For any precise layout work, very infrequent now-a-days, I use gauge blocks and set the scribing block to them. Using the blocks in conjunction with a dial gauge is also a great way to attain accuraccy but strive for three consecitive same readings to be sure.

  10. #10
    anteekfreek is offline Cast Iron
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    Dial or digital calipers ?

    To me, it makes no real difference.

    If a high level of accuracy is desired, then calipers aren't the tool for the job anyway. I only use calipers to measure features that do not require a high degree of accuracy.

  11. #11
    Clive603 is offline Titanium
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    It should be possible to trust any calibrated measuring instrument to within its smallest graduation when properly used! Should and is aint always the same.

    Vernier has least to go wrong and, unless abused, will maintain its accuracy at the standard to which it was made. Should be pretty much on the button, but if you have to its easy enough to check with gauge blocks.

    Dial caliper is easiest to read and probably clearest as a comparator when used as advised by J_R_Thiele due to the wider spacing of calibrations. The mechanical connection between rack and dial will have cyclic errors. Depending on quality these may or may not be of importance.

    Any analogue instrument can be read between graduations as a comparator, intrinsically impossible with digitals which have a fundamental digitisation error and can never be better than the least significant digit. Not forgetting the hysterisis built in to the change-over point to ensure that you get a stable reading.
    Good ones can be very consistent and trustworthy, bad ones can be all over the place. Many cheap ones are sensitive to the rate and /or direction of slider movement slider and its not uncommon to require a minimum move to give repeatable results. The errors may or may not be symmetrical. Repeatabily is often less than wonderful. Read the specifications for a quality digital, you will probably be disappointed. Then compare the claims for a supermarket special, almost invariably the same, sometimes better. Who do you believe?
    Generally digitals, even ex-supermarket, are repeatable least significant digit but I'd never trust them for precision to measured size. I used to work on development of optical test equipment / methods and had a lot of problems whilst the digital revolution settled down. Real precision and super repeatability takes a lot more engineering than is practical for a digital caliper.

    That said I tend to grab my 7.50 Lidl supermarket special digitals first and keep the better gear for when I need it.

    Clive

  12. #12
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    Default Vernier

    Quote Originally Posted by beege View Post
    I was told that digital indicators were more accurate than dials...

    It's not a matter of question.
    A vernier scale is itself the most accurate means of measurement PERIOD.

    This is due to the slide scale being directly proportional to the base scale.

    A digital-caliper is a magnetic vernier caliper.
    The magnetic reader is the equivalent of the slider, accept that it is actually
    twice the accuracy of it's smallest measurement-increment.
    Otherwise it wouldn't know when you reverced the direction of the tool.

    Cheers.

    m1m

  13. #13
    MikeJB is offline Aluminum
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    With any type of caliper it is best to read it while on the part; removing it from the part to read it will quite often disturb the measurement.

    In order of ease of reading the vernier is the trickiest, second is the dial, and digital is easiest.

    I'm talking about say a part still in the chuck or vice when you cannot always position it for a convenient reading.

    Oh, and I'm left handed so I always have to read it upside down........... Does anyone make left handed calipers or mikes?

    As for accuracy; my Mitutoyo digitals have always been spot on when comparing with a mike or gauge block. You do have to develop a 'feel' for it; sometimes I convince myself that I can interpolate within the resolution by the feel and the way the digits change with differing pressure. Am I imagining things?

    Regards,

    Mike.

  14. #14
    machine1medic's Avatar
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    Lightbulb

    QUOTE=MikeJB;990523With any type of caliper it is best to read it while on the part; removing it from the part to read it will quite often disturb the measurement.
    My Mititoyo 12" has a hold botton that will sustain the measurement as you removde the callipers.
    In order of ease of reading the vernier is the trickiest, second is the dial, and digital is easiest.

    Oh, and I'm left handed so I always have to read it upside down........... Does anyone make left handed calipers or mikes?

    sometimes I convince myself that I can interpolate within the resolution by the feel and the way the digits change with differing pressure. Am I imagining things?
    Phil

    Regards,

    Awareness, accute awareness, is the very heart and nature of a good machinist Or tool-maker.
    Just make-sure you can turn the accute awareness off when it's not needed or welcomed.

    Mike./QUOTE

  15. #15
    willbird is offline Banned
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    The dial caliper has one issue that the verniers and digital do not. That is WEAR...the rack can be worn where it is used the most, thus making that area of the measuring range read differently than the rest of the rack, typically this wear area is in the 0" to 1" range...which is right where you ZERO the caliper....making a measurement at 3" inaccurate. So I guess one should check for this with gage blocks from time to time.

    Bill

  16. #16
    Clive603 is offline Titanium
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    Default

    Quote Originally Posted by MikeJB View Post
    Oh, and I'm left handed so I always have to read it upside down........... Does anyone make left handed calipers or mikes?

    As for accuracy; my Mitutoyo digitals have always been spot on when comparing with a mike or gauge block. You do have to develop a 'feel' for it; sometimes I convince myself that I can interpolate within the resolution by the feel and the way the digits change with differing pressure. Am I imagining things?

    Mike.
    Left handed digital calipers are frequently advertised in the UK hobby press. Unfortunately those I've seen have only been from the usual "inexpensive" suppliers so you don't get that warm feeling about specifications.
    I have seen left handed versions of conventional verniers and micrometers but cannot recall the suppliers. Maybe Benson for the vernier as theirs were double sided with inside and outside scales on opposite sides and I'm sure I picked up one that was the opposite way round to mine causing great, but fortunately temporary, confusion when helping out in some-one else's lab.

    'fraid you are imagining things if you believe that you can get meaningful interpolation by changing the pressure on your Mitutoyo digital calipers. There is a lot going on in the signal processing and its a pretty spurious effect mostly due to hysterisis non-linearity and inequality. Neither meaningful nor reliable. Its easy to forget just how small a thou physically is and how lacking in beam stiffness the typical caliper is. To my mind the way a digital caliper sensor works is more a case of it not being how well the bear dances but that it dances at all.

    If you want precision grade sensing you need moire fringe and similar optical gap magnifying systems such as those on the sub micron resolution Heidenhain probes I used to use for lab work. Even with those, things could get seriously hairy below a thou' if you got careless and didn't think about what you were doing. As you can imagine calibrating was a pain!

    If, like Bill, you are worried about rack wear on dial calipers its easy enough to mark the starting zero position of the dial with a scribe mark across the rotating bezel and onto the surround. Be fairly obvious when its a thou out. personally I doubt if wear ever becomes a problem, reckon the cover "glass" will get scratched to blazes first. Now dirt and gunge I will believe having just had to clean out the rack and pinion of my 10 year old imperial dial after it got the "not nice feel" problem. Had to shift the dial by a thou or two when done, right back to where it was when new.

    Clive

  17. #17
    amklein is offline Plastic
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    After reading this thread, i took my 1" and 2" mit. mic standards and measured them with my starrett 120 6" dial calipers; the new ones with the plastic dial. about .9995 on the 1", spot on 1.999 on the 2" and with both standards stacked i got about 2.9985. good news is that its consistantly dropping the half thou every inch, bad news is that its 3 thou off over 6 inches. did the same thing with the mitutoyo digital calipers a buddy of mine has, no error at all.
    At the same time, i will say that i have noticed that those who use digital calipers are alot more inclined to mess up; its that damned zero button. alot of the kids never clean the jaws of their calipers and because of that they end up 3-5 thou under on a part with a 2 thou tolerance.
    Its been said before and ill say it again: its all in the person using them.

  18. #18
    hkrok is offline Banned
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    Of course, the digital one have high accuracy than dial one. From resolution you may know that
    Dial: 0.02mm
    digial 0.01mm.

    let alone the accuracy.

    www.roktools.com

  19. #19
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    Calibration is the Key, does not matter what kind of measuring tool you use as long as it is in good condition, calibrated and that you use it in a consistent fashion.

    A guy or girl from NASA would more than likely use Laser Metrology whilst a bush mechanic would scribe a mark on a stick with his pocket knife. It all depends on what you are trying to achieve and wether the tolerance you need is within your Metrology capabilities.

  20. #20
    hkrok is offline Banned
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    But Tools is the first, then calibration.
    If tools is not good, calibration will be useless.

    http://www.roktools.com
    tools factory for professional user.

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