Gage

Thread Limit Gages
Parallel Pipe Thread Gages G.PF
Taper Pipe Thread Gage
Standard Thread Gages ST
Limit Gages
Morse Taper Gages/National Taper Gages

 

 

Thread Limit Gages


ISO gage standards

Thread limit gages are rated according to the tolerance class of threads to be measured with them. Threads are judged acceptable if the go-gage smoothly and completely enters them but the no-go gage does not enter more than two turns. In addition to these JIS thread limit gages, we design and manufacture various types of thread gages based on every standard.

JIS gage standards

Thread limit gages are rated according to the tolerance class of threads to be measured with them. Threads are judged acceptable if the go-gage smoothly and completely enters them but the no-go gage does not enter more than two turns. In addition to these JIS thread limit gages, we design and manufacture various types of thread gages based on every standard.

-Differences between the ISO gage standard and the conventional JIS gage standard (or features of the ISO gage standard)

  • Check gages and production gages are not distinguished any more on both the go end and no-go end of gages.
    The ISO gage standard makes no distinction between the no-go end of check gages and that of production gages, though they were distinguished in the conventional JIS. Therefore, threads can be judged acceptable if they are proved to satisfy the standard through a check using either check or production gage which is known to meet the requirements (with possible wear being taken into consideration).
  • As gages for external threads, ring gages have been added to the snap gages in order to satisfy the Tayler's principle.
  • Pass/fail judgement of thread ring gages
    The conventional JIS gage standard provided that ring gages might be judged acceptable if the fit check gage smoothly entered them without producing play. In the ISO gage standard, however, thread ring gages are to be checked with two fit check gages: a go gage and a no-go gage, and they are judged acceptable if the go gage enters them smoothly and completely but no-go gage does not enter more than one turn.
  • Thread plug gage for checking wear
    The no-go end of thread plug gages for checking wear was not standardized by JIS, and therefore it was necessary for users to set their own standard for the no-go end of their gages, considering both the increase in the useful life of the gages and the decrease in the acceptance rate of the threaded products. Recently, however, the ISO gage standard has been introduced into JIS.

 

 

Parallel Pipe Thread Gages G.PF

Used to check parallel pipe threads. In the current JIS which has introduced the ISO gage standard, parallel pipe threads are referred to as 'G', instead of 'PF', as far as the ISO standard is concerned.

 

 

Taper Pipe Thread Gage

Gages R
Used to check taper pipe external and internal threads, and parallel pipe internal threads to be engaged with taper external threads. In the current JIS which has introduced the ISO gage standard, taper pipe threads are referred to as 'R' or 'RC', instead of 'PT', as far as the ISO standard is concerned.

Gages PT

In a check using this type of gage, pipe threads are judged acceptable if the end of the pipe or pipe joint (excluding the chamfer of parallel pipe internal threads) falls within the notched area when the gage is fitted and tightened by hand.
Gages ANSI Standard

Typical standards widely used at present
  • Ordinary threads: NPT (American (National) Standard Taper Pipe Thread)
  • Sealing threads: NPTF (Dryseal American Standard Taper Pipe Thread)
  • Aeronautical threads: ANPT (Aeronautical National Standard Taper Pipe Thread)

 

 

Standard Thread Gages ST

Every standard thread gage, composed of a pair of gages precisely fitted together, has nearly the same size as the basic size of applicable threads. To check a product thread with this gage, you need to fit it directly onto the thread in most cases.

 

 

Limit Gages

Every limit gage has two measuring end faces: one for the allowable maximum size of the hole or shaft and the other for the allowable minimum size. Since the tolerances of limit gages are set in connection with the tolerances of applicable product holes or shafts, and thus the levels of difficulty in manufacturing them vary depending on the tolerance, the tolerance ratings are set according to the rating of applicable holes or shafts and the type of limit gage.

 

 

 

Morse Taper Gages / National Taper Gages

Taper gages are used to check the tapers and reference diameters (diameters of the large and small end faces) of tapered products. This type of gage consists of a set of gages fitted together: a taper plug gage and a taper ring gage. Main types of taper are Morse taper, national taper and Brown & Sharp taper. Products can be judged by the point up to which their reference end face goes into the gage with a notch, or by the line drawn on the larger end face of the taper plug gage.

 

 

 

 

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