Choosing the Right Indicator
Indicators are instruments utilized in various contexts to measure small distances and angles and amplify them to make them obvious.
Machinists use this precision measuring tool in a great number of applications, ranging from determining the accuracy of a lathe or mill alignment to setting parts accurately on a faceplate.
Types of Dial Indicators
As any person who has worked in a machine shop will know, indicators exist in two different formats: Dial Indicators (DI) and Dial Test Indicators (DTI). So, what’s the difference between them and how to use them?
Dial Indicators
Dial indicators have plunger-type contacts. They are best used in situations where comparative measurements are necessary and are typically the best solution when repeatability is the main characteristic you are looking for.”. Dial indicators typically have larger dials than test indicators, making the visibility much better and easier to read. When it comes to fixture gaging applications the dial indicators will be better suited than the test indicator.
If you are going to be using the indicator for rapid quality inspection, it will be necessary to use a fixture gage with the dial indicator. Here’s what we and Abom79 recommend: Noga DG61003 Regular Duty Dial Gage Holder. This type of holder is what allows the dial indicator to perform.
Dial Test Indicators
Dial test indicators have lever-type contacts and are great for consistency measurements, like layout work or aiding in part setup as opposed to comparative measurements with gages and fixtures.
Additionally, because of the test indicators anatomy, they are more suited for measuring surfaces with irregularities. This is thanks to the angular motion of the lever. Because of this, they are great for machining setups with lathes and jig bores. Test indicators are also smaller and lighter than dial indicators.
When combined with a V-block or center, the test indicator can measure for roundness or runout specifically on cylindrical parts.
Both types of dial indicators are handy and relatively easy to use, and, although there are several overlapping applications, they are often used for separate tasks.
Although dial test indicators are generally used more often in job shops, we generally recommend having both. We asked the Practical Machinist community via Instagram and Facebook to share their favorite models. Here’s what they told us.
Recommended Dial Indicators
Brown & Sharpe 14.82022 Dial Indicator
The Brown & Sharpe dial indicator reads to 0.001”, with one revolution of the dial being 0.10”, and the total available measurement being 1.0”. The ball contact tip reaches into the workpiece to make accurate measurements of turned, milled, and ground parts, for tool setting gauges, fixtures, and inspections. The racks and bottom bearings are made of stainless steel for corrosion resistance. The central lug back can be rotated 90 degrees for vertical or horizontal use and the dial face is 2 1/4” in diameter.
Mitutoyo 2046S, 0.01mm X 10mm Dial Indicator
The Mitutoyo dial indicator has a stainless steel 8mm stem, lug back, and hardened steel spindle for quality and sturdiness. The indicator features a hard coated crystal for scratch resistance and technology for improved resistance to dust and water, making this tool great for a variety of shop environments. It also has a graduation of 0.01mm and range of 10mm.
Starrett 25-441J Dial Indicator
The Starrett dial indicator has a 0 to 1″ measuring range with 0.001″ graduations for precise measurement of the rise or drop in a workpiece. Made of shockless hardened steel, this dial indicator is a tough and durable measuring tool that will always provide smooth operation. Its gears, jeweled bearings, springs, bushings, and other components are all made with the finest quality construction to provide a mechanically solid indicator.
Fowler 52-585-115-0 Magnetic Base & Dial Indicator Combo Set
This Fowler dial indicator set has a 0 to1″ measuring range and is designed to measure variations within thousandths of an inch (0.001″). This set includes a dial indicator, magnetic base and fitted storage box. The magnetic base has an 85lb pull and the ability to mount indicators with a 1/4″ post.
Mahr Federal B7I AGD 1 Dial Indicator
The Mahr Federal dial indicator is used to measure dimensional deviations. It has a measurement range of 0 to .75″, graduations of 0.0005″, an accuracy of ±0.0005″, and a range per revolution of 0.050″. The dial is light green for easy reading and includes inch recognition with a contrasting hand, for readability. he dial is balanced with a reading of 0-25-0, for comparative readings.
Recommended Dial Test Indicators
Mitutoyo 513-406-10E Horizontal Test Indicator
The Mitutoyo dial test indicator features a .079″ carbide contact point. Uusers have expressed high praise about this tool for its smooth use and accurate readings. This test indicator has graduations of .0005″/0.01mm, a range of .030″/0.7mm, and a dial face of 0-15-0/0-35-0.
TESA Brown & Sharpe 01889023 Dial Test Indicator
This Brown & Sharpe dial test indicator is a lever-type indicator with a 1.5″ dial diameter, 0.0005″ dial division, 0.030″ range, 0-15-0 marking, and a black face for clear readings. This dial test indicator measures with +/-0.0001” accuracy making it both reliable and affordable. This model also features a dovetail mount.
Fowler 52-562-778-0 Dial Test Indicator
This test indicator includes bidirectional constant clockwise rotation, automatic reversal, three dovetail mountings, jeweled movement, two dovetail clamps and a molded case. This test indicator has a range of 0.030”, dial reading of 0-15-0 and graduation of 0.0005”.
Starrett 711GPSZ Last Word Dial Test Indicator
The Starrett dial test indicator has a balanced dial, swiveling body, and inch measurements. The horizontal-face dial test indicator has a hard, chrome-plated, steel ratchet contact point for taking precise measurements in machining, layout, and inspection work. This dial test indicator features a jeweled lever action for smooth operation, and replaceable contact point.
Digital Indicators
Dial indicators are available with digital readouts too, although most machinists prefer the analog dial. If you are a digital tools advocate, Mitutoyo has a great option:
Mitutoyo 543-783B Absolute Digimatic Indicator
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7 Comments
Of minor concern when setting up a test indicator is the orientation of the contact arm to the work movement, and is specific to manufacturer and even model. Some provide optimum accuracy when positioned at 90 degrees to the work; some specify that they are calibrated at a 15 degree angle. The difference in reading is usually insignificant, but is measurable (“sine error”).
its actually a cosine error and only applies to test indicators that have the lever arm for measurement.the 15deg is the angle between the lever arm and the surface being measured. if the angle is greater than 15 degs, the length of the lever arm is foreshortened to the point that it affects the measurement. compute the cosine of 15 deg=.966, its pretty close to 1. that value times the length of the lever arm is the foreshortened length which is less than the the calibrated lever arm length.
@davidanderson – well explained sir.
Newbie asks: Does dial seller usually provide angle/arm-length look-up tables? Or, a formula? Your description instantly alerted me before buying.
Thanks.
Interapid???
I would re-edit this article. The B&S and Fowler test indicators shown in this article are not trustworthy.
How can you list dial test indicators without having Interapid at the top? It’s not even on the list at all! Makes it hard to take this article seriously..