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

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 the secondary sector of the economy. The term may refer ...

machining Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which util ...

, and

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

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

measurement Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to ...

s (the

range Range may refer to: Geography * Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra) ** Mountain range, a group of mountains bordered by lowlands * Range, a term used to i ...

), 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 () has traditionally been a Solid geometry, three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a Prism (geometry), prism with a circle as its base. A cylinder may ...

, 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 In various contexts of science, technology, and manufacturing (such as machining, metal fabrication, fabricating, and additive manufacturing), an indicator is any of various instruments used to accurately measure small distances and angles, and w ...

; 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" (noun) refers to any imperfection of form that causes a rotating 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); eccentricity (that is, lacking sufficient

concentric In geometry, two or more objects are said to be ''concentric'' when they share the same center. Any pair of (possibly unalike) objects with well-defined centers can be concentric, including circles, spheres, regular polygons, regular polyh ...

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, threading and turning, with tools that are applied to the w ...

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 Surface roughness or simply roughness is the quality of a surface of not being smooth and it is hence linked to human ( haptic) perception of the surface texture. From a mathematical perspective it is related to the spatial variability structure ...

, where both peaks and valleys count toward an assessment of the magnitude of roughness. Statistical methods such as

root mean square In mathematics, the root mean square (abbrev. RMS, or rms) of a set of values is the square root of the set's mean square. Given a set x_i, its RMS is denoted as either x_\mathrm or \mathrm_x. The RMS is also known as the quadratic mean (denote ...

(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 Cosine error is a type of measurement error caused by the difference between the intended and actual directions in which a measurement is taken. Depending on the type of measurement, it either multiplies or divides the true value by the cosine of ...

. 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 of ...

s, which still say "TIR"; and (2) generations of machinists were trained with the term "TIR", whereas only recent curriculum uses "FIM". Image-Comparateur ovale.png, Measuring roundness Comparateur rectitude.png, Measuring flatness

References

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

See also

References