Help figure out this dial test indicator
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    Default Help figure out this dial test indicator

    Hello everyone!
    It's my first post, I'm a software developer and a beginning hobby metalworker.

    I've got a dial test indicator stand on eBay, and was wondering if someone could tell me about this style of stand. I haven't seen similar stands so far. Bundled together was an accessory, looks like some kind of holder, but I can't really figure out it's usefulness (it's the metal two-part piece on the right from the indicator stand).

    The stand came with a 0.01 mm Compact dial test indicator, which seems to be working fine, however at rest the revolution counter is pointing closer to 1 than 0. I can work with that by remembering this, but I wonder if that is normal, or if not, is there any way to adjust the rev counter's position?

    Thanks in advance for all the tips, and please excuse my non-native English (I'm a Russian living in Luxembourg).

    Best regards
    --Gene

    img_20190418_203139884_hdr.jpgimg_20190418_203212253.jpgimg_20190418_203204947.jpgimg_20190418_203159366.jpg

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    As for the dial reading at rest, that really doesn't matter. This type of indicator is TYPICALLY used to measure variations in a surface, rather than a linear dimension. The indicator is typically brought close to the workpiece, then the indicator is adjusted so that the tip is touching the workpiece. You can tell this when the dial reading deflects slightly. You can then rotate the dial until it reads "0", then either rotate the workpiece (as in a lathe) to read the variations in the surface, or if the indicator is mounted on a stand, move the indicator over the surface to read the differences. I realize my descriptions are very broad, but I'm trying to minimize any confusion due to the language differences.

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    Looks like it's attached to some sort of magnetic base, although I don't see a lever to turn the magnet off/on. Usually used to indicate part runout on the lathe.

    You could remove the stem from the mag base and hold it in a collet in the mill to indicate a vise square or tram the head.

    The dovetail on the indicator should also fit other styles of test stand to increase it's versatility.

    No idea what the 2-pc block is for. Looks homemade.

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    Quote Originally Posted by Booze Daily View Post
    Looks like it's attached to some sort of magnetic base, although I don't see a lever to turn the magnet off/on. Usually used to indicate part runout on the lathe.

    You could remove the stem from the mag base and hold it in a collet in the mill to indicate a vise square or tram the head.

    The dovetail on the indicator should also fit other styles of test stand to increase it's versatility.

    No idea what the 2-pc block is for. Looks homemade.
    I'm agreeing with this. If there is no "maker's name" on anything then I'm guessing "home made". Using that type indicator with a magnetic stand (that has ON and OFF) is the normal method.

    I'm also curious as to why you bought it. You must have felt you could use it for something.

    "Na zdorovje"

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    I have seen a couple of magnetic bases like that used on lathe ways, with a long travel plunge style indicator, to fine indicate carriage travel when one doesn't have a DRO. The typical use I've seen was to place the indicator so that it reads carriage movement towards the chuck and use it to repeatable turn to a shoulder. The advantage over using the carriage wheel increments is that there is no backlash worry about.

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    Thanks you everyone for your replies. Really lovely forum, I can feel how much collective knowledge people have in here!

    The base is indeed magnetic, but there is no on/off switch like practically all the other mag bases I've seen for sale.
    Lacking that switch, I imagine it could be quite awkward to use, hence I'm wondering what it used for.

    I bought it mostly for the indicator itself, when I saw it was a Compac (heard good things about those), but was hoping the stand or it's parts would also be useful. I am also waiting for another switchable mag base with central clamping.
    I want to use it to check shafts or brake discs for runout, as well as surfaces for flatness. It's good to know that I don't have to worry about the rev counter pointing rather far from 0 at rest, however am still curious if that condition is fixable (although from childhood experience I think that if I open that clock, I'll probably break it).

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    The rev counter should indeed be near zero when indicators are relaxed. Naturally, you can use it "as is" unless you have a huge deviation on the surfaces being tested which is not usually a case.

    As for "fixing" it, it can be as simple as repositioning the hand, but it can also be more complicated IF THE INDICATOR IS INDEED DEFECTIVE. In any case, I don't suggest you to mess with it if you don't have experience in fixing those.

    Strangely enough, some brand new Compacs do have the rev counter hand close to "1" at rest. Frankly, I don't know the rational behind this design, but IIRC, I have one of those.

    At the same time, there are other indicators where the rev dial hand is a bit beyond zero (in the negative zone). This does make sense because you preload the stem against the surface being tested, and this will bring the rev dial hand closer to zero.

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    On by bestest indicator of that type you can also move the indicator arm. I would think yours is the same. It is just held by friction so a gentle push of the arm should reposition it to where you want it.

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    Rev counter hand a bit in the negative zone makes more sense, indeed. How about the main dial, is it normal for it to be at 8 o'clock at rest? Perhaps for applying that amount of preload to bring it to 12 o'clock?

    I'd try gently pushing the rev counter hand, how does one safely remove the crystal though?

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    Quote Originally Posted by gene-pavlovsky View Post
    Rev counter hand a bit in the negative zone makes more sense, indeed. How about the main dial, is it normal for it to be at 8 o'clock at rest? Perhaps for applying that amount of preload to bring it to 12 o'clock?

    I'd try gently pushing the rev counter hand, how does one safely remove the crystal though?
    A haiku comes to mind...
    It worked before
    Messed with it you did
    Got what you deserved

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    Quote Originally Posted by Hazzert View Post
    A haiku comes to mind...
    It worked before
    Messed with it you did
    Got what you deserved
    Sounds more like Yoda to me.

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    It moves plus and minus.
    I should not be at zero unloaded and if so it is broken.
    So the tiny pointer is at one on the dial. Real sure that this is not negative one?
    Bob

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    Quote Originally Posted by gene-pavlovsky View Post
    Rev counter hand a bit in the negative zone makes more sense, indeed. How about the main dial, is it normal for it to be at 8 o'clock at rest? Perhaps for applying that amount of preload to bring it to 12 o'clock?
    That's not a problem at all although I'd prefer to have the handle at 10 or 11 o'clock position at rest.

    I'd try gently pushing the rev counter hand, how does one safely remove the crystal though?
    Rob didn't talk about the handle. He meant the indicator contact point.


    Bob answered the question about the rev handle. He says that this model allows probing in both directions: positive(0 to +2mm range) and negative (0 to -1mm range). So at rest it's suspended in between rather than being at a terminal position. IMHO, if this is a case, the marks on the rev dial are quite confusing. I'd expect to see a scale from -1 to +2 with handle at zero at rest.

    If I find my Compac of this type, I'll check it.

    EDIT: I got interested and searched the Web for Compac 212L and 210 series. Strangely enough, I found two types of 212L: one with the dial like yours where the rev handle is at 1. And another one where the handle is at zero.

    compac 212l - Google Search

    The manual for Ser.210 shows your type of 212L, but says nothing about negative direction measurement. Go figure!


    But the good news is that your Compac seems to looks like it was designed.

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    Great, now I know that the lever position can be adjusted by pushing (a bit more than I would call "gentle", but nothing extreme). I guess this is the feature mentioned in the catalog of these DTIs as "Friction lever system to preventing overload" (not so proper English, isn't it?).

    Curiously, that google search turns up with the product page on Amazon UK with the rev counter at 1. The User manual for these DTIs shows it with the rev counter at 1. The catalog shows it with the counter at 0, though. I am curious what would be a sensible purpose of having the counter at 1. I will try to contact Compac (Tesa) to ask this.

    Note: on this indicator, the hand always travels clockwise, regardless of the measuring direction. Whether the lever is pushed to one direction or another, the measurement works in the positive direction in either case. So I can't figure what would be the purpose of the "negative zone" (below 1 on the rev counter).

    At maximum deflection the rev counter shows beyond 3 (roughly where 4 would be), so the usable range can be 3 full turns indeed. And also if I preload the contact point so that the indicator hand points to 12 o'clock, the rev counter points exactly to 1. So it does seem like it is working like it was designed.

    The disconcerting thing I just found out by looking at the manual (and seeing the picture of the product on Amazon UK) - 212L is supposed to have 36 mm long lever, giving 3 mm measuring range. However my indicator has a 18 mm long lever, which does actually move only 1.5 mm. I suppose the previous owner installed a non-standard contact point, does doing this actually double the measurement precision? Because one graduation that is supposedly 0.01 mm is effective 0.005 mm?

    And that haiku... I've done it too many times, so I'm more cautious now. Having said that, each time I did so, I learned something

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    Dial test indicators (unlike dial or travel indicators), due to the cosine error, are used only for comparative measurements in most cases. So your short probe shouldn't concern you THAT much. Indeed, if you replace a long probe (contact point) with a short one, your indicator will become more sensitive. But having it more sensitive can be a plus if the decreased overall range doesn't limit you. The dial test indicators would show correct value only when the probe is perfectly parallel to the surface (and its length is as designed) which is not how they're usually used anyway. In those cases where you really want to see near real values, you can always recalculate the readings taking into consideration both, the probe length and the cosine error.

    As for the probe angulation, you can change it as you describe if it's stated so. Most, but not all dial test indicators allow it, and then you'd have to manipulate the whole device to position the probe which is not always convenient.
    Last edited by MichaelP; 04-25-2019 at 10:59 PM.

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    Thanks, I learned a lot in this thread already!

    But I suppose it can be used to get a ballpark figure of how flat is some surface, or a shaft/axle runout? Using this test indicator I will have to factor in cosine error correction, and then multiply by 0.5 as well because my probe is half the nominal size. Or can these measurements be taken using a dial (travel) indicator (if so, how)? I also got a used 0-10/0.01 mm Mitutoyo dial indicator.

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    Quote Originally Posted by gene-pavlovsky View Post
    Note: on this indicator, the hand always travels clockwise, regardless of the measuring direction. Whether the lever is pushed to one direction or another, the measurement works in the positive direction in either case. So I can't figure what would be the purpose of the "negative zone" (below 1 on the rev counter).

    At maximum deflection the rev counter shows beyond 3 (roughly where 4 would be), so the usable range can be 3 full turns indeed. And also if I preload the contact point so that the indicator hand points to 12 o'clock, the rev counter points exactly to 1. So it does seem like it is working like it was designed.
    I think if you get the indicator against a workpiece (in lathe, or?) and adjusted so it is reading 1 1/2 turns in (center of travel) then you will see a useful reading in both directions. 1 1/2 turns positive and 1 1/2 turns negative.


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