Height and depth gauges are bench-top and portable dimensional instruments dedicated to measuring heights, bore depths, steps and references with respect to a surface plate. Together with straightedges and gauge blocks, they make up the fundamental equipment of workshop and metrology-room measurement. The most widespread variants are mechanical vernier height gauges, digital models with a high-resolution encoder, and motorized height gauges with absolute measurement on a precision column.
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Measuring principles
The height gauge consists of a vertical column and a moving carriage that slides along it with a measuring jaw. The Z=0 reference is the surface plate (granite or ground steel). Digital models use inductive or magnetic transducers for position measurement, with resolutions down to 0.001 mm and zero-setting, statistical and USB/Bluetooth output functions. Depth gauges consist of a bearing crossbar and a movable depth rod, with a graduated scale or a digital sensor. Gauge blocks are the primary length standards in the workshop, in classes K (reference), 0, 1 and 2 according to ISO 3650.
Technical characteristics
Height gauges cover measuring ranges from 0-300 mm to 0-1000 mm and beyond. The latest generation of motorized models integrates high-sensitivity probes for 2D measurements (heights, distances, bores, squareness) with accuracies of ±2 μm over 300 mm. Depth gauges follow the same arrangement as vernier calipers, with resolutions of 0.02-0.01 mm and typical accuracies of ±0.02 mm over 0-200 mm. Gauge blocks provide calibrated nominal lengths, with tolerances in the μm range depending on the class.
Applications
Motorized height gauges are the benchmark for advanced workshop metrology: they allow dimensional measurements of batches of parts on a surface plate with dedicated software, considerably reducing times compared with a CMM while offering accuracy suited to tolerances typically down to IT6/IT7. Depth gauges are used to check blind holes, grooves, steps and seats for washers and bearings. Gauge blocks are the reference instrument for calibrating calipers, micrometers and dial indicators and for setting up machine tools.
Standards
Height gauges comply with ISO 13225, depth gauges with ISO 13385-2 and gauge blocks with ISO 3650 (previously DIN 861). Periodic calibration of height gauges is carried out on a surface plate with certified blocks, and on motorized models with integrated calibration software. Metrological traceability must go back to primary national standards through an ISO 17025 chain.
Selection criteria
The choice of instrument depends on the measuring range, the resolution, the need for 2D functions (squareness, bores, distances), integration with CAD software and report management, the availability of a suitable surface plate, portability (for the manual depth gauge) or fixed installation (for high-precision motorized models).
In industrial practice, the height gauge is an instrument of transition between workshop equipment and the metrology room: on motorized models with a touch-trigger probe, the operator performs complete dimensional and geometric measurements without the need for a CMM, with limited investment and high productivity. Managing the data with dedicated software allows dimensional reports to be generated automatically with full traceability.
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