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Comparative Measurement Instruments; Gages

Fixed Comparative Gaging Instruments In Quality Control


Fixed comprative gaging instruments are used in various kinds of manufacturing sites and quality control departments. They are very simple to use to understand whether the workpiece inside the define tolerances or not. In this article, we will explain the general types of fixed comparative gages, and where to be used them.

What Is Fixed Gaging Instrument?

If we take a look at the classification of fixed gages, there are two types;

Master Gages: These fixed gages are generally produced in the size of nominal workpiece. You can directly gage the workpiece to compare its sizes with the nominal size of ideal workpieces.

Limit Gages: These gages has two of gaging, one of them is for upper tolerance of nominal size and one of them for the lower tolerance of nominal size of the ideal workpiece.

Consider about that you are using a limit gage for measuring a internal diameter of a workpiece specimen. If we want to say that this specimen OK, there must be two of conditions satisfied;

  • Specimen must not fit to the upper tolerance measurement side of limit gage,
  • Specimen must fit to the lower tolerance measurement side of limit gage.
Snap gaging instrument.

The reverse logic is valid for external measurements with limit gages.

C shaped snap gages are generally used for the measuring the external diameters and the ring gages are generally used for measuring internal cylindrical diameters. These are the limit gages that are generally used in quality control sites.

Also there are special limit gage types such as thread gages to measure the threaded surface characteristics of a specimen. Also tapered gages can be used for internal measuring.

Plug gaging instrument for external measurements.

As we said before, if a limit gage is produced for specific nominal sizes with specific tolerances, they give very fast information about whether the produced specimen inside the defined tolerances and sizes or not. But we could not take the exact measurement information of specimens with these fixed gaging instruments.

High speed electronic gaging instruments are taking the place of conventional fixed gaging instruments in manufacturing and quality control departments today.

Fixed comparison gaging instruments can be explained like above basically. Don’t forget to leave your comments and questions about ‘Fixed Gaging Instruments’ below!

Image source: Fundamentals of modern manufacturing.

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