Like the vernier caliper, the caliper height gage consists of a stationary bar or beam and a movable slide. The graduated , hardened , and ground beam is combined with hardened , ground, and lapped base. The venier slide assembly can be raised or lowered to any position along the bar. It can be adjusted in thousandths of an inch (U.S. customary system) or hundredths of a millimeter (metric system) by means of the vernier slide fine-adjusting knob. The primary uses of caliper height gages are for either layout or measurement . They are commonly used for marking off vertical distances and for measuring height differences between steps at various levels. When marking off distances scribers are attached to the contact jaw. A dial indicator is typically attached to the height gage for making comparison measurements . However , height gages are notorious for inaccurate measurements due to their large height-to-base length ratio.
The basic design principles of vernier caliper gages are also apllied in caliper height gages.Vernier height gages differ from caliper gages in that they have a single jaw, because the surface plate on which the instrument base rests functions as the reference plane. Vernier gages usually have offset jaws whose contact surfaces can be brought to coincide with the reference plane when the slide position indicates zero height.
The nonintegral reference plane requires great locating stability and internal rigidity from height gages in order to maintain a beam position that is substantially perpendicular to the surface plate. Consequently , with the exception of the less accurate models , vernier height gages are made with wide bases and with bars of strong cross-section; the bars carry the same kind of graduations found on the beams of vernier calipers. For marking off purposes , scribers can be attached to the contact jaw. These scribers are designed to have the edge substantially at equal level with the contact surface of the jaw, in order to make the height of the scribed line coincident with the dimension indicated by the gage.