Page 67 - Personal Study Notes (Engineering Metrology - 22342)

Page 67 of 176

Limitations or Disadvantages of Limit Gauges:
1. Do not Indicate Exact Size:

Limit gauges do not indicate exact size of the component. They only indicated
whether the component is within the tolerance zone or not.

2. Errors due to Wear:
Limit gauges are subjected to errors due to wear of gauges during use.

3. Difficulty in Checking of Finer Tolerance:
It is generally uneconomical to manufacture a limit gauge with 0-0.0013 mm

tolerance, to check the work tolerance of about 0.013mm. Such fine limit gauges are
also difficult to use in shop-floor, due to wear.

Q. Write short note on Need of Limit Gauges.

Need of Limit Gauges:

There are two methods to ensure whether the components being produced on the shop
floor are as per the pre-decided specifications or not.

These are:

(i) Measurement by measuring instruments.
(ii) Limit Gauging by fixed design limit gauges.

Obviously, measurement is the best method, but is not practical to check every
dimension on each manufactured part. On the other hand, Limit gauging is faster,

easier, and does not required skill inspector.
Also, accuracy of component greatly reflects itself in the cost of the product. To achieve

a greater accuracy than necessary, it makes the project uneconomical. Thus, in
repetition work it is not possible to check dimensions with the precision instruments like

vernier, micrometer etc. This conventional measurement requires skilled or semiskilled
workers.

Hence, in mass production where inter changeability is to be maintained at relatively low

cost, the dimensional tolerance (high and low limits) are controlled by the limit gauges.

Engineering Metrology (Only For Personal Use) 24