metrology Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fra ...

and the fields that it serves (such as

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ...

, machining, and

engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

), total indicator reading (TIR), also known by the newer name full indicator movement (FIM), is the difference between the maximum and minimum measurements, that is, readings of an

indicator Indicator may refer to: Biology * Environmental indicator of environmental health (pressures, conditions and responses) * Ecological indicator of ecosystem health (ecological processes) * Health indicator, which is used to describe the health o ...

, on the planar,

cylindrical A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an in ...

, or contoured surface of a part,{{cite web , url=http://www.engineersedge.com/engineering/Engineering_Terms_Glossary/T/total_indicator_reading_tir_4448.htm , title=Total indicator reading (TIR) , accessdate=2011-03-31 , url-status=dead , archiveurl=https://archive.today/20120729021818/http://www.engineersedge.com/engineering/Engineering_Terms_Glossary/T/total_indicator_reading_tir_4448.htm , archivedate=2012-07-29 showing its amount of deviation from flatness, roundness (circularity), cylindricity, concentricity with other cylindrical features, or similar conditions. The indicator traditionally would be a dial indicator; today dial-type and digital indicators coexist. The earliest expansion of "TIR" was total indicated run-out and concerned cylindrical or tapered (conical) parts, where "

run-out Run-out or runout is an inaccuracy of rotating mechanical systems, specifically that the tool or shaft does not rotate exactly in line with the main axis. For example; when drilling, run-out will result in a larger hole than the drill's nomina ...

" (noun) refers to any imperfection of form that causes a

rotating Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...

part such as a shaft to "run out" (verb), that is, to not rotate with perfect smoothness. These conditions include being out-of-round (that is, lacking sufficient

roundness Roundness is the measure of how closely the shape of an object approaches that of a mathematically perfect circle. Roundness applies in two dimensions, such as the cross sectional circles along a cylindrical object such as a shaft or a cylindr ...

); eccentricity (that is, lacking sufficient

concentric In geometry, two or more objects are said to be concentric, coaxal, or coaxial when they share the same center or axis. Circles, regular polygons and regular polyhedra, and spheres may be concentric to one another (sharing the same center ...

ity); or being bent axially (regardless of whether the surfaces are perfectly round and concentric at every cross-sectional point). The purpose of emphasizing the "total" in TIR was to duly maintain the distinction between per-side differences and both-sides-considered differences, which requires perennial conscious attention in

lathe A lathe () is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, and turning, with tools that are applied to the workpiece to ...

work. For example, all depths of cut in lathe work must account for whether they apply to the radius (that is, per side) or to the diameter (that is, total). Similarly, in shaft-straightening operations, where calibrated amounts of bending force are applied laterally to the shaft, the "total" emphasis corresponds to a bend of half that magnitude. If a shaft has 0.1 mm TIR, it is "out of straightness" by half that total, i.e., 0.05 mm. Today TIR in its more inclusive expansion, "total indicator reading", concerns all kinds of features, from round to flat to contoured. One example of how the "total" emphasis can apply to flat surfaces as well as round ones is in the topic of surface roughness, where both peaks and valleys count toward an assessment of the magnitude of roughness. Statistical methods such as

root mean square In mathematics and its applications, the root mean square of a set of numbers x_i (abbreviated as RMS, or rms and denoted in formulas as either x_\mathrm or \mathrm_x) is defined as the square root of the mean square (the arithmetic mean of th ...

(RMS) duly address the "total" idea in this respect. The newer name "full indicator movement" (FIM) was coined to emphasize the requirement of zero cosine error. Whereas dial test indicators will give a foreshortened reading if their tips are on an angle to the surface being measured (cosine error), a drawing callout of FIM is defined as referring to the distance traveled by the extremity of the tip—not by the lesser amount that its lever-like action moves the needle. Thus a FIM requirement is only met when the measured part itself is truly in geometric compliance—not merely when the needle sweeps a certain arc of the dial. The "TIR" abbreviation is still more widely known and used than "FIM". This is natural given that (1) many part designs that are still being manufactured are made from decades-old

engineering drawing An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number o ...

s, which still say "TIR"; and (2) generations of machinists were trained with the term "TIR", whereas only recent curriculum uses "FIM".

References

* http://gdtseminars.com/2008/11/17/whats-the-difference-between-tir-and-fim/ Mechanical engineering Machining

See also

References