How to Use a Dial Test Indicator: Setup, Cosine Error, Tramming, Centering and Runout (with Mitutoyo TI Models)
A dial test indicator (DTI, lever-type indicator) is the tool machinists reach for to tram a vise, center a part in a four-jaw chuck, find a bore center or check runout. It is also an indicator that is easy to misread, because its lever arm has to sit at the right angle to the surface. This guide covers setup, the angle rule (cosine error) with Mitutoyo's own correction table, the four everyday jobs, zeroing and reading, and the mistakes that ruin an indicator. At the end we list the Mitutoyo TI-series test indicators we ship from Japan.
- Mount it on the shortest, stiffest holder you can (a magnetic base on the machine, or a comparator stand).
- Swing the lever arm so it is parallel to the surface being checked. The tip must move perpendicular to the surface, not slide across it.
- Our method: preload the tip a little way into its range so it can read both ways.
- Turn the bezel to set the needle to zero.
- Move the part (rotate the spindle, slide the table) and watch the needle. Our method: read the total swing as the deviation.
- If the arm had to sit at an angle, correct the reading with the cosine table below.
What a dial test indicator does (and what it does not)
A plunger-type dial indicator senses movement along its spindle axis. A test indicator senses movement perpendicular to the shaft of its contact point: the stylus is the end of a small lever that pivots, and that pivot is turned into needle movement (Modern Machine Shop; University of Florida design lab). The payoff is reach: the tip gets into bores, under edges and onto side faces while the dial stays where you can see it. The price is a short range. The Mitutoyo TI models we stock cover 0.14 mm to 1 mm of total range, so a test indicator is a comparison tool, not a tool for measuring how far something travelled. If you are still deciding between the two types, read Dial Test Indicator vs Dial Indicator: How to Choose.
Setting up
1. Mounting
Flex in the holder shows up as reading error. The University of Florida design lab's guidance is to use the shortest, stiffest stand base possible. Mitutoyo's Quick Guide gives a mounting rule for dial indicators, align the spindle with the intended measuring direction when you clamp it, and in our view the same logic applies to a test indicator, because that is the first place cosine error creeps in. The TI models we stock list a 6 mm mounting shaft on their product pages (the TI-129HX page does not state it); dovetail mounting details are Not confirmed on our pages.
2. Set the stylus angle: the cosine rule
This is the step that separates a good reading from a wrong one. Mitutoyo's Quick Guide states that an indicator reads accurately only when its measuring direction matches the intended direction, and tells you to minimize the angle θ between the measuring direction and the line through the contact point and the stylus pivot. Modern Machine Shop describes the same thing in practical terms: if the arm is not parallel to the part, the tip slides across the surface as well as moving along the measurement direction, and the steeper the angle, the larger the error. The arm is held by a friction clutch, so you can swing it into position even when the indicator body is at an angle.
When the angle cannot be eliminated, Mitutoyo gives a compensation table. Multiply the dial reading by the factor:
| Stylus angle θ | Multiply the reading by | Example: dial shows 0.200 mm |
|---|---|---|
| 10° | 0.98 | 0.196 mm |
| 20° | 0.94 | 0.188 mm |
| 30° | 0.86 | 0.172 mm (Mitutoyo's own example) |
| 40° | 0.76 | 0.152 mm |
| 50° | 0.64 | 0.128 mm |
| 60° | 0.50 | 0.100 mm |
Compensation values from Mitutoyo's Quick Guide to Precision Measuring Instruments. The 0.200 mm rows other than 30° are our arithmetic using those factors. Mitutoyo also mentions a custom involute-form contact point that compensates automatically from 0° to 30°.
Two practical consequences (our reasoning from the table). First, for alignment jobs (tramming, centering) you rarely need to correct, because you are driving the needle to zero and the cosine error scales the deviation but does not move the zero. Second, for a measurement job (runout in millimetres, a step height) you must either get the arm parallel or apply the table. Modern Machine Shop notes that ignoring cosine error can lead to rejecting good parts or accepting bad ones.
3. Keep the standard contact point length
Because the stylus is a lever, the indicator is calibrated for its standard contact length. Modern Machine Shop warns that a longer or shorter contact changes the lever ratio and causes measurement errors. Mitutoyo's Quick Guide gives the thread as M2.5 × 0.45, 5 mm long, for anyone making a special point. The TI-129HX we stock is Mitutoyo's long-point version with a carbide tip and double scale width; its product page does not state the length (Not confirmed).
4. Preload and zero
Bring the tip onto the surface and push it a little into its range, so the needle can move in both directions. Then rotate the bezel until the needle sits on zero. QSource describes this as the first step in using a test indicator: get the hand pointing to zero on the face dial. The TI models whose product pages list a dial reading (for example 0-40-0 on the TI-113HX) use balanced dials, so the needle reads the same amount either side of zero.
The four everyday jobs
Tramming a vise or fixture
Our method: mount the indicator in the spindle or on the head, set the tip on the fixed jaw with the arm parallel to it, zero, then traverse the table along the jaw. The needle shows how far the jaw is out of line over that distance. Tap the vise until the needle stays at zero end to end. The University of Florida lab's advice is to clean the fixed jaw first (they use Scotch-Brite); our note is that a chip or burr under the tip reads as misalignment.
Centering a part in a four-jaw chuck
Our method: set the tip on the outside of the part, zero, and rotate the chuck by hand. The high and low readings tell you which jaw to loosen and which to tighten. Repeat until the needle barely moves through a full turn. A balanced dial such as 0-40-0 makes this easy to read because the needle swings either side of zero.
Finding a bore center on a mill
Modern Machine Shop's example is aligning a bore to the machine spindle: with the indicator in the spindle and the tip inside the bore, rotate the spindle by hand and (our method) adjust the table until the needle stays at zero all the way round. This is the job where the test indicator's reach matters, since a plunger indicator cannot get into the bore while the dial stays visible.
Checking runout
Our method: set the tip on the rotating surface (a shaft, a chuck, a tool holder), zero, and turn it through one revolution. The total needle swing is the total indicated runout. Because this is a measurement rather than an alignment, get the arm parallel to the surface or apply the cosine table. Our pick for fine runout work such as a spindle nose or a collet is the TI-111HX, whose 0.001 mm graduation shows deviations a 0.01 mm graduation cannot.
Reading the dial
The dial shows graduation and range together: a TI-113HX reads 0.01 mm per division with a 0-40-0 face, so one full sweep from one end to the other is 0.8 mm. The TI-111HX reads 0.001 mm per division on a 0-70-0 face over 0.14 mm. The University of Florida lab's rule for choosing is to pick the lowest resolution that does the job, because it is also the cheapest. Mitutoyo notes, for dial indicators, that measuring force is lower with the spindle horizontal or the contact point up and that repeatability should be checked in those positions; we treat that as a reason to check a test indicator the same way. The TI models we stock list a measuring force of 0.3 N or less (TI-123HX and TI-123HRX: 0.2 N or less; TI-129HX: not stated).
Mistakes that ruin an indicator or the reading
- Dropping it, or slamming the stylus. The University of Florida lab states that dropping an indicator or rapidly accelerating the stylus ruins its accuracy, and asks users to report any accident so the tool can be tested.
- Oiling the mechanism. Mitutoyo's Quick Guide says, for dial indicators, not to lubricate the spindle, as oil attracts dust, and to clean with a dry or alcohol-dampened cloth instead; we apply the same care to a test indicator's lever (our note).
- Over-tightening the clamp. Mitutoyo warns that excessive clamping torque affects movement. For stem-mounted indicators it gives a maximum of 150 N·cm with a single M5 screw and a clamp position at least 8 mm from the stem's lower edge.
- Dirty surfaces. Errors from calibration, cosine error, hysteresis and dirty parts compound (University of Florida).
- Measuring at the wrong temperature. Mitutoyo specifies permissible errors at 20 °C.
- Treating a test indicator like a dial indicator. For parts that vary a lot in height, the University of Florida lab prefers a plunger (drop) indicator; a test indicator's 1 mm or shorter range will run out.
Mitutoyo test indicators we stock
All 13 are Japanese-market models and list Japan as the country of origin. Models with "R" in the name list a ruby ball contact point. The full specification table (range, graduation, dial reading, measuring force) is in our test indicator vs dial indicator guide; here is the short version by job.
Picks by job
General setup: tramming, centering
TI-113HX (513-404-10H)
0–0.8 mm, 0.01 mm, 0-40-0 dial, 40 mm dial, 6 mm shaft, 45 g.
View TI-113HX
1 mm range, 0.2 N or less
TI-123HX (513-415-10H)
0–1 mm, 0.01 mm, 0-50-0 dial, measuring force 0.2 N or less.
View TI-123HX
Deep bores: long point
TI-129HX (513-414-10H)
0–0.5 mm, 0.01 mm, long point, carbide tip, double scale width.
View TI-129HX
Ruby ball contact
TI-113HRX (513-474-10H)
Same range and dial as the TI-113HX, with a ruby ball contact point.
View TI-113HRXWe also stock the TI-111HRX, TI-112HX, TI-112HRX, TI-212HX, TI-133HX, TI-133HRX, TI-123HRX and TI-213HX; see all Mitutoyo test indicators. For a reference surface, see the granite comparator stands; note that the stands list an 8 mm hole and the TI models a 6 mm shaft, so ask us about holding a TI on a stand before ordering. We do not currently stock magnetic bases.
Why a Japanese-market Mitutoyo test indicator (facts we can confirm)
- All 13 TI models list Japan as the country of origin on their product pages.
- Each page states measuring range, graduation, dial reading and measuring force, so you can match the tool to the job before buying.
- Mitutoyo's own Quick Guide, which this article follows, is the manufacturer's method for cosine compensation and mounting.
- We list the Japanese model names (TI-113HX) and manufacturer codes (513-404-10H); if you searched for a different code, compare by the specification.
- We ship from Osaka and check each item in Japan before it goes out.
FAQ
How much does a small angle matter?
Mitutoyo's table gives a factor of 0.98 at 10°, so a 0.100 mm reading is really 0.098 mm. Modern Machine Shop's example is a 5° angle on a 0.010 in reading, for which it calculates 15 microinches, far below what a mechanical test indicator can resolve or repeat. Our rule of thumb: above 20° (factor 0.94) it is large enough to matter for measurement, though not for driving a needle to zero.
Can I measure a step height with a test indicator?
Only within the indicator's range (1 mm or less on the TI models) and with the arm parallel to the surface. For larger steps use a plunger indicator on a stand.
Which way should the stylus point?
Mitutoyo's rule is to set it so the angle θ between the measuring direction and the line from contact point to pivot is as small as possible; in practice, arm parallel to the surface. The friction clutch lets you swing it to that position.
Do these indicators read in inches?
The models here are metric (mm) Japanese-market models. Whether an inch-reading version of each exists is Not confirmed on our pages; if you need an inch dial, ask us before ordering.
Related
- Mitutoyo Dial Test Indicator vs Dial Indicator: How to Choose
- Mitutoyo Measuring Tools: Which One Measures What You Are Working On
- Mitutoyo Micrometer Buying Guide
- Mitutoyo test indicators
- Mitutoyo dial and digital indicators
Shipped directly from Japan
We ship genuine Mitutoyo instruments from Osaka with tracking (Japan Post, FedEx or DHL), and check each one before it leaves. For US orders, import duties are included in the price.
Browse Mitutoyo test indicatorsSources
- Mitutoyo, Quick Guide to Precision Measuring Instruments: Dial Indicators and Dial Test Indicators: cosine compensation table and example, stylus angle rule, contact point thread, mounting and clamping limits, measuring force, 20 °C, no lubrication
- Modern Machine Shop, "Versatility With Test Indicators": how test indicators sense movement, contact length and lever ratio, cosine error, friction clutch, bore alignment example
- University of Florida MAE Design Lab, "Use of Indicators": test vs drop indicators, tramming, four-jaw centering, bore centers, cosine error, hysteresis, do's and don'ts
- QSource, "What Is a Dial Test Indicator, How Is It Used, and What Is It For?": zeroing as the first step
- Product specifications (range, graduation, dial reading, measuring force, shaft, weight, country of origin): Mitutoyo catalog data shown on each linked product page
