Question about my dial indicator

Discussion in 'Garages, Workshops & Tools' started by 76_TypeLT, Oct 5, 2014.

  1. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

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    Jul 26, 2008
    Houston, TX
    I got a dial indicator to use when I eventually dial in my bellhousing. I got the FIRST one pictured below. My question is why does the dial go from 0 to 15 back to 0? The needle only sweeps in one direction regardless of which way the needle moves so I am curious why this dial indicator is designed this way. It will work fine for this purpose since the alignment tolerance is up to 0.005".

    I see that other dial indicators go from 0 to 100, like the 2nd picture below. So there must be a reason for the difference between these two styles.

    [​IMG]

    [​IMG]
     
  2. mickstan

    mickstan Veteran Member

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    Jun 11, 2012
    E'ville, IL
    well , first thing I notice is that the bottom one measures by "pushing in" on the rod. The top one "swings". I'm guessing the top one only measures to 15 thousandths, the bottom one will go to 100 thousandths. The top one would be good for measuring the face of the bell housing, and the bottom for measuring the bore.
     
  3. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

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    Jul 26, 2008
    Houston, TX
    Thanks for chiming in. The top one, which is the one I have, measures to about 0.040" since it does one full revolution and then a little more.

    I read a little more and I assume the one I have can be set such that the dial can be rotated such that 0 = 15 and then you can more easily see +/- movements.
     
  4. grzewnicki

    grzewnicki Veteran Member Lifetime Gold Member

    The plunger type (2nd one) is going to work better for you than the lever. The lever type is mostly used by machinists when they are setting up a machine. I have both types and the lever type was just about impossible to use, of course I was doing mine under the car. I did weld up some brackets to bolt my plunger indicator to so it ran right inside the bore of the bell. And another bracket so it could do the face of the bell.
     
  5. CamaroDoc

    CamaroDoc Veteran Member

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    The lever type is for centering a part on a mill or lathe or squaring up a machine that has been moved or repaired. When the indicator is initially set in place it is located so that the lever in contact with the surface to be trued, moves the lever about half way through it's travel. The dial is then rotated so that the 0 is in line with the needle. As the part is then rotated, the dial sweeps in either direction and the machine can be adjusted whichever way necessary to center or "zero" it.


    .
     
  6. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

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    Jul 26, 2008
    Houston, TX
    Good info, thanks for clearing that up.

    I will try to use the dial indicator I already have, but only because the engine is out of the car so it will be easier to manage. I still have the option to exchange it, so I will go that route if necessary.
     
  7. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    Oct 2, 2013
    Milford,CT
    If you use the first indicator, put about .007 of pressure on it from a resting position, (sweet spot). Set the dial to the 5 marking, and not to zero. That way, when it touches more, you'll read a bigger number on the dial. When it touches less, you'll read a smaller number on the dial. If you set it to zero, it will read a bigger number each way, and you'll have to remember which way is which, (tough to do in a mirror at times as well). I use indicators every day. Good luck.
     
  8. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

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    Jul 26, 2008
    Houston, TX
    That's good advice, thank you.
     
  9. NeoNeuro

    NeoNeuro Veteran Member

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    Aug 4, 2014
    Panama City, FL
    The first one is called a "run-out" indicator. As others have mentioned, it is used for measuring the +/- variation from a zero point. They are typically used on rotating assemblies to measure what is essentially wobble, or variation from center (run-out). To use this type you typically pre-load and zero it near the center of the measuring tip's travel. This gives you more or less even amounts of + and - travel. These types tend to have rather small measurement ranges, but are generally more accurate. Accuracy of +/-.0001" is not uncommon.

    The second type is a basic travel dial indicator. These are the most common type and are the most versatile. There isn't much you can't measure with these if you have a good set of mounting adapters. They have much larger measurement ranges. (A 6" range is not uncommon and I've seen them go to a full foot.) Accuracy is usually +/-.001" in the first inch of travel and gets worse with each additional inch. Note that these can also be used to measure run-out like the first type, but these are not as accurate if you're working with close tolerances. To use you should pre-load the dial about 1/4 of a revolution and set the zero there.

    With all dial indicators, repeatability is the biggest factor in how good they are. If you take a measurement and can't get it to come back to the same zero point, you either have something loose in your measurement setup or the indicator is trash. The first thing most guys do is open up the back, grab the WD-40, and hose it down. That's actually the worse thing you can do. The gears inside of these things are of watchmaker quality and precision. The oil is too heavy and just makes matters worse. They'll never work right again. The best thing to do is a good (gentle) cleaning, but that's hard to do without damaging the internals. Generally, it's worth a shot, but don't get your hopes up. The easy path is to just get a new one. Give the old one to your kids and watch their fascination. They'll play with it for hours.

    Source: I used to calibrate these for the USAF and USMC. I have literally worked on hundreds upon hundreds of these things. Thanks for the flashback. :)
     
  10. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

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    Jul 26, 2008
    Houston, TX
    That's great info, thanks man. I notice the indicator I bought has a fairly small travel range, which coincides with what you are saying. Again, since the max tolerance for dialing in the bellhousing is 0.005" then this one should work. I will report back after I do this job.
     

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