Test & Inspection
Calipers, micrometers, indicators, height and bore gauges, gauge blocks, laser distance meters and coordinate measuring equipment.
Dimensional measurement covers two quite different things that share a catalogue. The first is the handheld tool used at the machine - a caliper or a micrometer - which tells an operator whether a feature is inside tolerance right now. The second is the reference layer in the inspection room - a gauge block set, a setting ring, a coordinate measuring machine - which establishes the length everything else is compared against.
They are not interchangeable, and treating them as one class is the most common error in this category. A caliper that displays a fine resolution does not measure to that resolution, because the jaws deflect, the beam is offset from the measuring line and the part is rarely at the temperature the instrument was calibrated at. A gauge block set is accurate precisely because it avoids all three of those problems, and it is bought to transfer that accuracy rather than to measure production parts.
The practical consequence is that the drawing tolerance, not the instrument, comes first. Work backwards from the tolerance to the uncertainty the measurement has to hold, and the class of instrument follows - along with the temperature control, the fixturing and the calibration traceability that go with it.
| Product type | How it measures | Usually specified for |
|---|---|---|
| Digital caliper | A linear encoder reads the jaw position on a beam that slides over a scale | Shop-floor checking of external, internal and depth dimensions where reading speed matters more than the tightest uncertainty |
| Vernier caliper | A sliding vernier scale read against a main scale, with no battery or electronics involved | Workshops where power or electronics are unwelcome, and where the tool has to survive rough handling |
| Micrometer | A precision screw advances a spindle against the work, with the reading taken from the thimble | Single dimensions at tight tolerance - shaft, sheet, wire and coating thicknesses - where a caliper would not be defensible |
| Dial or digital indicator | A plunger or lever converts displacement into a reading against a zeroed reference | Comparative measurement: runout, flatness, deflection and seating, where the value of interest is a difference rather than an absolute size |
| Bore gauge | A two- or three-point head is set against a ring or master and then read in the bore | Internal diameters that a caliper cannot reach properly, and any bore where roundness and taper matter |
| Height gauge | A vertical column with a scriber or a measuring head, referred to a surface plate | Marking out and checking heights and steps from a datum, frequently on castings and machined bodies |
| Gauge block set | Accurate rectangular blocks wrung together into a stack of known length | Establishing and transferring the reference for every other instrument, and for the calibration chain in the inspection room |
| Coordinate measuring equipment | A probe is driven to points on the surface and the geometry is computed from the coordinates | Complex geometry, many features on one part, and inspection records that have to be stored and reported |
Depth gauges, measuring gauges, laser distance meters and general precision measuring instruments are listed under this category as well.
There is rarely a single correct instrument for a duty, but there is always a shortlist that can be justified and a set of answers that eliminates the rest. These are the questions that decide it.
| Instrument class | Best suited to | Limits | Typical use |
|---|---|---|---|
| Handheld caliper with encoder | Fast checks across many features on a production part | Jaw deflection and the offset between the scale and the measuring line limit what the reading can support; resolution is not accuracy | External, internal and depth dimensions |
| Micrometer with a precision screw | A single dimension where the tolerance is tight and the geometry is simple | One frame covers a limited span, and the measuring force and the part temperature both influence the result | Shaft, sheet and wire diameters |
| Comparative indicator | Measuring a difference against a setting master, and finding form errors | Produces a displacement rather than a size, so the master and the fixturing are part of the measurement chain | Runout, flatness, deflection |
| Bore gauge with a setting ring | Internal diameters where a caliper cannot be presented squarely to the feature | The setting ring is in the chain, and misalignment in the bore reads as a size error | Hole and bore diameters |
| Gauge blocks | Holding and transferring the length reference itself | Requires care, cleanliness and temperature control; a worn or damaged block propagates its error into everything calibrated against it | Reference length and calibration |
| Coordinate and optical measurement | Complex geometry, many features, and results that have to be recorded | Needs a controlled environment, a trained operator, and a part that can be presented and located repeatably | Complex and recorded geometry |
What is left after the technology is chosen is a list of values that only the installation can supply. These are the ones that change the model, the price or the lead time:
Specifications vary by model and application, so no performance figure is stated on this page. Where a parameter has not been documented for a particular model, the product page says so rather than filling the gap with a plausible number. Send the values above and we will return the ones the selected model actually holds.
Frequently asked
The questions that come up before an order rather than after it. If yours is not here, send it with the requirement and we will answer it in the quotation.
No, and this is the assumption that causes most of the trouble in this category. The resolution is the smallest change the display can show, while the accuracy is what the instrument can actually support once jaw deflection, the offset between the measuring line and the scale, the measuring force and the part temperature are taken into account. For a tight tolerance, the tolerance decides whether a caliper is the right instrument at all.
By the tolerance and by what has to be measured. A micrometer controls the measuring line and the force much better, which makes it the defensible choice for a single close dimension such as a shaft or a sheet thickness. A caliper is faster and reaches more features, which suits general checking and dimensions that are not close to the limit. Many inspection stations keep both and use them for different features.
Because length measurements are referenced to a standard temperature, and a metal part changes size as it moves away from that condition. A part taken straight off a machine, or a workshop that is considerably warmer or cooler than the reference condition, will measure differently. It matters most when the tolerance is tight, and it is one of the reasons a measurement that is perfectly repeatable in the inspection room can disagree with one taken at the machine.
If the measuring instruments are used to make decisions against a tolerance, the chain they are set and checked against has to exist, and gauge blocks are the usual way of providing it. Without them the instruments are only verified at their own calibration interval. The blocks are also the reference for setting rings and for any comparative gauge used on the shop floor.
For most instruments, yes, and it should be stated at the enquiry stage because it affects both price and lead time. Say which certificate the quality system expects and what it has to be traceable to, since a certificate that names the wrong reference is of no use in an audit. Where a certificate cannot be provided for a particular model, we would rather say so before the order.
When the geometry is complex, when many features have to be related to each other, or when the results have to be recorded and reported rather than read from a dial. It also needs a controlled environment and a part that can be located repeatably, so it is normally an inspection-room instrument. Where a drawing calls for a form or position tolerance across several features, a handheld tool cannot answer the question at all.
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DVC-150 · Digital Calipers Reference listing
Stainless steel digital caliper with a capacitive encoder, 0.01 mm resolution and four measurement functions, in hardened and hardened stainless construction.
Send the specification and we will confirm the matching instrument, availability and lead time. Minimum order quantity is 1 pc.
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Send the technical detail and we will confirm availability, lead time and terms. In-stock items ship within 48 hours; customized specifications typically take 2-10 days. Minimum order quantity is 1 pc.