Can someone clue me in as to what each is best at? I mostly use a dial indicator to tram my HF mini mill, and frankly, it's a pain. I've seen DT indicators also recommended for this, though...are they any better at this application, or just different?
(I hope I have the names right...by "dial indicator" I mean the one where the pin can just move in and out, and by "dial test indicator" I mean the one where the pin swings.)
Dial indicator vs. dial test indicator
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rbuzaleski
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- Location: Cleveland, OH
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toastydeath
- Posts: 176
- Joined: Fri Aug 10, 2007 8:00 pm
- Location: Newark, DE
Dial indicators are better at measuring actual motion. If you want to move .050", you use a dial indicator.
Dial test indicators are comparative devices - if you want to compare the height, position, et cetera of two things. DTIs generally have a lighter spring pressure than a dial indicator, and come in a smaller package. You can fit them in small bores and other spaces where it would be impossible to fit a dial indicator. But a DTI works off angular displacement, which does not measure linear distance very well over anything but small distances.
Dial test indicators are comparative devices - if you want to compare the height, position, et cetera of two things. DTIs generally have a lighter spring pressure than a dial indicator, and come in a smaller package. You can fit them in small bores and other spaces where it would be impossible to fit a dial indicator. But a DTI works off angular displacement, which does not measure linear distance very well over anything but small distances.
Types of Indicator
I am by NO MEANS a Expert on indicators .
I have used both types and mostly the horizontal dial test type . They come in Vertical and horizontal .
The dial with the push pin / rod / bar has different size buttons that can be used with it . It is usually much more forgiving when sliding over ridges / edges etc . I never felt they where as accurate as the dial test with the small arm / finger .
The dial test that has the arm that comes in different lengths and different size ball end is less for giving when traming over ridges and edges etc .
Over all i always felt that these finger / arm type style where more accurate , or should I be saying more sensitive to a smaller given area .
The dial test finger type is more fragile than the other .
Well this is what I feel and have observed with my usage of them .
I can say that the nicest and most accurate and least repairs was my Interapid Dial Test in .0001 and .0005 reading . Was just sooo smoooth and nice to use .
JerryL
I have used both types and mostly the horizontal dial test type . They come in Vertical and horizontal .
The dial with the push pin / rod / bar has different size buttons that can be used with it . It is usually much more forgiving when sliding over ridges / edges etc . I never felt they where as accurate as the dial test with the small arm / finger .
The dial test that has the arm that comes in different lengths and different size ball end is less for giving when traming over ridges and edges etc .
Over all i always felt that these finger / arm type style where more accurate , or should I be saying more sensitive to a smaller given area .
The dial test finger type is more fragile than the other .
Well this is what I feel and have observed with my usage of them .
I can say that the nicest and most accurate and least repairs was my Interapid Dial Test in .0001 and .0005 reading . Was just sooo smoooth and nice to use .
JerryL
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Toasty has it dead to rights and simply stated.
DTI: Various tips available, with different balls and what not, but length is critical and can't be changed without blowing the scale. Used for checking parallel surfaces, tramming a head, centering a 4 jaw chuck, etc. Orientation is not all that critical, but better accuracy if you can keep the "finger" more or less at right angles to travel. I have B&S "BestTest" in 0.001, 0.0005, 0.0001. These are my "every day" or "go to" DTIs for most things. A Federal in 0.00005 (very short finger). And an Interrapid 0.0001 that is truely "sweet". I don't care for the Starretts. These are used mostly on an Indicol for the mill, or a special holder for setting the lathe 4 jaw, dialing a compound taper, or setting the tailstock. Also used on the surface plate with a surface gage when accuracy of measure is not critical.
DI: Various tips available in a HUGE range of styles, diameters, AND lengths. Linear operation means length does not matter to resolution, but orientation is EVERYTHING! If it's not perpendicular to measurement, you reduce accuracy. Used for accurately quantifying measurements. While a DTI used in a surface gage on a surface plate can tell you that a surface is out, and which way, with a "feeling" for magnitude, an equivalent resolution DI, while not as smooth and "easy" to use, will tell you exactly (within accuracy limits) how far out it is for a given offset (that bar is parallel to less than 0.001 per foot). I have various Geneva, Starrett, Federal, and others in a variety of travels, dial sizes, and resolutions. I also have a set of SPI "tips" that increase the utility quite a lot. These are used mostly on comparator stands, surface gages, or travel indicators for the lathe.
DTI: Various tips available, with different balls and what not, but length is critical and can't be changed without blowing the scale. Used for checking parallel surfaces, tramming a head, centering a 4 jaw chuck, etc. Orientation is not all that critical, but better accuracy if you can keep the "finger" more or less at right angles to travel. I have B&S "BestTest" in 0.001, 0.0005, 0.0001. These are my "every day" or "go to" DTIs for most things. A Federal in 0.00005 (very short finger). And an Interrapid 0.0001 that is truely "sweet". I don't care for the Starretts. These are used mostly on an Indicol for the mill, or a special holder for setting the lathe 4 jaw, dialing a compound taper, or setting the tailstock. Also used on the surface plate with a surface gage when accuracy of measure is not critical.
DI: Various tips available in a HUGE range of styles, diameters, AND lengths. Linear operation means length does not matter to resolution, but orientation is EVERYTHING! If it's not perpendicular to measurement, you reduce accuracy. Used for accurately quantifying measurements. While a DTI used in a surface gage on a surface plate can tell you that a surface is out, and which way, with a "feeling" for magnitude, an equivalent resolution DI, while not as smooth and "easy" to use, will tell you exactly (within accuracy limits) how far out it is for a given offset (that bar is parallel to less than 0.001 per foot). I have various Geneva, Starrett, Federal, and others in a variety of travels, dial sizes, and resolutions. I also have a set of SPI "tips" that increase the utility quite a lot. These are used mostly on comparator stands, surface gages, or travel indicators for the lathe.
Russ
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