Total indicator reading

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.

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).

Today TIR in its more inclusive expansion, "total indicator reading", concerns all kinds of features, from round to flat to contoured.

Statistical methods such as root mean square (RMS) duly address the "total" idea in this respect.

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.