ASME B89.1.7-2009 pdf download.Performance Standard for Steel Measuring Tapes.
4 GENERAL REQUIREMENTS All steel measuring tapes covered by this Standard shall conform to the requirements in paras. 4.1 through 4.9. 4.1 Straight and Parallel Steel measuring tapes shall be made so that when stretched out on a flat surface the edges are nominally straight and parallel. 4.2 Ease of Reading All steel measuring tapes shall be clearly marked to facilitate easy and correct reading. 4.3 Background The graduations and numbering shall be in sharp visual contrast with the background. 4.4 Compatibility There shall be compatibility between the legibility of graduations and the size and form of numbers, when related to the distance at which the measuring tape is normally read. 4.5 Measurement Units Unit names and symbols displayed on metric measuring tapes covered by this Standard shall be con- sistent with IEEE/ASTM SI 10-2002. 4.6 Graduation Requirements Along the nominal length, the measuring tape shall carry clear, regular, and indelible graduations and num- bering, to ensure simple and unambiguous reading. Some unnumbered graduations may extend beyond the major graduation marks at the ends of the measuring tape. Graduations extending to the left of zero and to therightofthe lastmajorgraduationarenotto beconsid- ered part of the tape for calibration purposes. 4.6.1 Graduation Quality. When the graduations are lines, they shall be visually straight, perpendicular to the axis of the measuring tape, and all of the same thickness. The thickness of each line shall be constant throughout its length. The lines shall be such that they form a distinct and clear graduation and that their thick- ness does not cause inaccuracy of measurement. Certain sections of the measuring tape, especially towards the ends, may be subdivided into submultiples of the graduation interval adopted for the whole mea- sure. In that case, the thickness of the lines may be less in the areas of reduced graduation intervals than in the rest of the measuring tape. 4.6.2 Arrangement. The measuring tape shall be divided by graduations of units consistent with the SI system or U.S. Customary system. The SI units shall be in meters, centimeters, millimeters, and multiples or subdivisions thereof. The U.S. Customary units shall be in feet, inches, and multiples or subdivisions thereof, to include decimal or fractional divisions. 4.6.3 Length of Graduations. In general, as the sub- division of length becomes smaller, the subdivisions should be indicated by using graduations of shorter length. However, in no case should the length ofgradua- tions be less than 0.7 mm or 0.03 in. 4.6.4 Width. The graduation marks shall not be wider than 50% ofthe distance between two consecutive minor graduations. 4.7 Additional Markings All markings, other than graduations and numbering, should be so positioned and of such a size as not to interfere with the legibility of the steel measuring tapes.
4.9 Definition of the Calibrated Distance The calibrated distance between graduations shall be taken as the intervals between the centerlines of pairs of graduations at the edge of the tape where the shortest graduations appear. In the absence of short graduations, the calibrated distance is defined to be the intervals between center- lines of the graduations at the bottom edge of the tape when viewed with the numbers right side up. The dis- tance is defined at20°C, when the tape is fullysupported with specified tension (possibly zero) applied (see section 6). It should be noted that cases exist that are not covered above. Inthese cases the ownershould specifythedefini- tion of the calibrated distance. In the absence of a clear definition, the calibrating technician shall use his or her discretion in defining the calibrated distance, and the definitionofthe calibrated distance shallbe documented in the calibration report. 5 STEEL MEASURING TAPES This Standard applies to numerous tapes, as described in paras. 5.1 through 5.4. 5.1 Retractable Steel Tape Rule A retractable steel tape rule is a graduated and num- bered flexible steel blade with either a curved cross sec- tion that provides a measurable degree of stiffness, or a flat rectangular cross section, with an end fitting and optionally a spring motor within a case. It is to be con- structed in a manner that allows easy extension and provides for quick retraction into the case.