Difference between Line Standards and End Standards(Comparison Chart)

Difference between Line Standards and End Standards

Contents

A length may be measured as the distance between two lines or as the distance between two parallel faces. So, the instruments for direct measurement of linear dimensions fall into two categories.

Characteristic	Line Standard	End Standard
Principle	Length is expressed as the distance between two lines.	Length is expressed as the distance between two flat parallel faces
Accuracy	Limited to ± 0.2mm for high accuracy, scales have to be used in conjunction with magnifying glass or microscope	Highly accurate for measurement of close tolerances up to ± 0.001 mm.-
Ease and time & measurement	Measurement is quick and easy	The use of end standards requires skill and is time-consuming.
Effect of wear	Scale markings are not subject to wear. However, significant wear may occur on leading ends. Thus it may be difficult to assume zero of scale as a datum.	These are subjected to wear on their measuring surfaces
Alignment	It cannot be easily aligned with the axis of measurement.	Can be easily aligned with the axis of measurement
Manufacture and cost	Simple to manufacture at a low cost.	The manufacturing process is complex and the cost is high
Parallax effect	They ate subjected to parallax error	They ate not subjected to parallax error
Examples	Scale (yard, meter etc.)	Slip gauges, end bars, V-caliper, micrometers etc.

When the length is measured as the distance between centers of two engraved lines, it is called line standard.
Both material standards yard and meter are line standards.
The most common example of line measurements is the rule with divisions shown as lines marked on it.

Characteristics of Line Standards

Scales can be accurately engraved but the engraved lines themselves possess thickness and it is not possible to take measurements with high accuracy.
A scale is quick and easy to use over a wide range.
The scale markings are not subjected to wear. However, the leading ends are subjected to wear and this may lead to undersize measurements.
A scale does not possess a “built-in” datum. Therefore it is not possible to align the scale with the axis of measurement.
A scale does not possess a “built-in” datum. Therefore it is not possible to align the scale with the axis of measurement.
Also, the assistance of a magnifying glass or microscope is required if sufficient accuracy is to be achieved.

When a length is expressed as the distance between two flat parallel faces, it is known as end standard.
Examples: Measurement by slip gauges, end bars, ends of micrometer anvils, vernier calipers, etc.
The end faces are hardened, lapped flat and parallel to a very high degree of accuracy.

These standards are highly accurate and used for measurement of close tolerances in precision engineering as well as in standard laboratories, tool rooms, inspection departments, etc.
They require more time for measurements and measure only one dimension at a time.
They are subjected to wear on their measuring faces.
Group of slips can be “wrung” together to build up a given size; faulty wringing and careless use may lead to inaccurate results.
End standards have built-in datum since their measuring faces are f l at and parallel and can be positively locked on the datum surface.
They are not subjected to parallax effect as their use depends on feel.