Holders, bases, stands and clamping systems form an infrastructure that is indispensable to the correct use of measuring instruments. They ensure stable positioning of the dial indicator or other instruments with respect to the workpiece, repeatability of the measurements, fine adjustment of dimensions, alignment and squareness. Without an adequate holder, even the most precise measuring instrument cannot deliver reliable results. They are used in the machine shop, in the metrology room, on test benches and in multi-gauge quality control stations.
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Types of holder
Magnetic bases use a permanent magnet or a lever-switched electromagnet to anchor themselves to ferromagnetic surfaces, with a holding force from 60 N to over 1000 N. They are fitted with columns, articulated arms and clamps for holding the dial indicator or the lever indicator. Bench stands are high-rigidity columns, generally in granite or cast iron, mounted on surface plates for precision measurements. Universal holders (V-shaped bases, articulated arms, prisms) are applied to specific geometries.
Technical characteristics
The rigidity of the holder is a critical parameter: elastic deformations in the order of a micrometer can compromise the measurement. Professional bases are made of cast iron or hardened steel, with ground surfaces to ensure flatness and parallelism. Articulated arms have high-grip friction joints, adjustable in numerous degrees of freedom. The fine adjustment allows settings in the order of a hundredth of a millimeter. The bearing surfaces must ensure stability even with a substantial mass of mounted instrument.
Levelling systems
Precision measurements of straightness, flatness and squareness require correct levelling of both instrument and workpiece. High-precision mechanical vial levels (sensitivity 0.02-0.1 mm/m), digital electronic levels with resolutions down to 0.1 μrad and laser alignment systems are used for this. Precision squares, radius gauges and straightedges are used for angular references.
Applications
Typical use includes mounting dial indicators on lathes and grinders for workpiece centring, setting up multi-gauge dimensional control stations, checking the flatness and squareness of mechanical components, aligning machine tools and checking surface plates. Magnetic bases are particularly versatile, because they can be transferred quickly from one machine to another.
Selection criteria
The choice depends on the dimensions and weight of the instrument to be mounted, on the anchoring force required, on the degrees of freedom of adjustment needed, on rigidity, and on the presence of ferromagnetic surfaces for magnetic bases. For measurements of the highest precision, granite stands on certified surface plates are preferred. For intensive workshop use, magnetic bases with an articulated arm are the ideal compromise between versatility and robustness.
The most modern holders integrate position sensors (magnetic or optical encoders) on their own adjustment axes, allowing the coordinates of the measuring point to be acquired automatically and the geometry of the workpiece to be reconstructed: they thus become low-cost dimensional measuring stations for workshop applications, an alternative to high-end CMMs. Wireless connectivity makes it possible to transfer the data directly to the production management system.
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