Measure difficult parts

Measure difficult parts

زهرة شوبينج اونلاين    يناير 07, 2011   

 Making it easy to measure difficult parts

An engineer might design the components, but someone on the production floor eventually has to measure them precisely.
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And until now, few handheld tools could accurately measure distances to theoretical sharp corners, apexes, mold lines, and intersection points.



CornerCalipers from SPS Industries, Farmington, Conn., (www.spsind.com), solves this problem by letting one (single-pivot model) or both jaws ( doublepivot model) conform to slanted walls. The pivot point is precisely located on the bottom edge of the device's caliper beam. So as the pivot jaw rotates, it stays at the zero reading of the caliper. The device can be used on sheet metal, plastics, casting, and extrusions, and on any parts with slanted or drafted walls.

It comes in 6, 8, and 12-in. sizes with resolution and repeatability to 0.0005 in. An LCD powered by a 1.55-V silver-oxide button battery shows results. The singlepivot model measures angles from 35 to 160°, while the doublepivot version handles 20 to 160°.

Terminology of measurement

Terminology of measurement

زهرة شوبينج اونلاين    نوفمبر 27, 2009   

Indicated size

This is the size indicated by the scales of a measuring instrument when
it is being used to measure a workpiece. The indicated size makes no
allowance for any incorrect use of the instrument, such as the application
of excessive contact pressure.

Reading

This is the size as read off the instrument scales by the operator. Errors
can occur if the scales are misread, for example sighting (parallax) errors
can occur when measuring with a rule. Vernier scales are particularly
easy to misread in poor light. A magnifying lens is helpful even in
good light and even if you have good eyesight. Electronic measuring
instruments with digital readouts overcome many of these reading difficulties.

Reading value

This is also called the ‘reading accuracy’. This is the smallest increment
of size that can be read directly from the scales of the instrument. It
will depend upon the layout of the scales. A micrometer caliper normally
has a reading value of 0.01 millimetre. A bench micrometer fitted with
a fiducial indicator normally has a reading value of 0.001 millimetre. A
vernier caliper with a 50 division vernier scale normally has a reading
value of either 0.01 millimetre or 0.02 millimetre depending upon how
the scales are arranged.

Measuring range

This is the range of sizes that can be measured by any given instrument.
It is the arithmetical difference between the largest size which can be
measured and the smallest size which can be measured. For example,
a 50 mm to 75 mm micrometer has a measuring range of 75 mm −
50 mm = 25 mm.

Measuring accuracy

This is the actual accuracy expected from a measuring instrument after
taking into account all the normal errors of usage. It can never be better
than the indicated size.