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Measuring tools are sensitive instruments of surface hardened steel provided with scales of different degree of accuracy. Simple measuring tools are mainly used in single-part production and maintenance work.
Steel rule and tape rule:
Measuring tools of 1 mm graduation mainly used for coarse measurements at easily accessible measuring points with the tool always to be placed at right angles to the locating edge.
Figure 3 Location of the steel rule
Figure 4 Location of the tape rule
Vernier caliper:
Predominantly used instrument, mostly of 1/10 mm graduation. Specially formed jaws permit outside, inside and depth measurements.
Figure 5 Measuring of inside
dimensions by means of the vernier caliper
Depth gauge:
Special instrument of 1/10 nun measuring accuracy for depth measurements of slots, shoulders and bore holes.
Depths of bore holes are always measured at the border (never in the centre!)!
Figure 6 Measuring of a slot depth by
means of the depth gauge
Outside micrometer:
Instrument of 1/100 mm measuring accuracy for precision measurement of outside measures in certain measuring ranges. For inside and depth measurements inside and depth micrometers are used.
Figure 7 Measuring by means of the
outside micrometer
Dial gauge:
Special instrument of 1/100 mm measuring accuracy for precision measurement in differential and concentricity measurements in batch production.
Figure 8 Use of the dial gauge in
differential measurements
Protractor:
Instrument for measurement of angles from 0 to 180 degrees with 1 degree graduation, suitable for coarse measurement only.
Figure 9 Protractor used for coarse
measurements
Universal bevel protractor:
Instrument for measurement of angles from 0 to 360 degrees with 1 degree graduation, with vernier providing for a reading accuracy of 1/12 degree - suitable for precision measurements.
Figure 10 Universal bevel protractor
In the use of measuring instruments faulty measurements may occur as a result of:
- Faults at the measuring instrument (damage):Check any measuring instrument for serviceability before use (slide vernier caliper into zero position and compare scale and vernier; check for external damage). Inaccuracies of measuring instruments may also be the result of too wide manufacturing tolerances or maladjustments!
- Faults caused by wrong use:
The measuring instrument is to be used for the proper purpose and range of accuracy. Too big measuring forces (deflections), oblique location or location on faces or edges not cleaned or deburred may result in wrong values measured. Moreover, reading errors may be a consequence of inadequate lighting or wrong conversion of the indicated values.
- Faults caused by environmental conditions:
Measuring instruments and workpieces are subject to heat expansion and low-temperature contraction. This may lead to different measuring results for the same object measured. To have a comparative value, measuring and testing tools are mostly adjusted at 20° Celsius.
Notes:- Avoid faulty measurements, if possible - measure twice at least I
- Use serviceable measuring tools only!
- Handle the measuring instrument properly!
- Ensure good conditions at the place of measurement - adequate lighting and cleanliness!
- Take the measurements at comparable temperatures, if possible I
Which measuring tools have a measuring accuracy of 1/10 mm?
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Which measuring tools are used for precision measurements of 1/100 mm measuring accuracy?
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What are the specific features of angle measuring instruments? How can measuring errors be avoided?
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