Order Information


Priority Rush Service is available for all our product line. Redline Service will be quoted per individual job for price and delivery

CALL NOW TO ORDER (800) 988-1566

  • Please order by description (plug, trilock, taperlock, ring, etc) then quantity, size, class, then direction of tolerance (go, nogo, or master)
  • “Complete” (handle with a go and nogo plug member) are best ordered by: quantity, go size, nogo size, class, and the word “complete”
  • WARRANTY – Zero Check warrants all gages for 30 days from date of shipment except in cases of obvious customer abuse or mishandling. Zero Check offers no further warranties expressed or implied, and its responsibilities due to any defects or inaccuracies in any gage or certificates shall, in no event nor for any cause whatsoever, exceed the purchase price of the subject gage
  • SPECIAL MARKINGS – Identifying size and class are permanently stamped or etched at no extra cost, any additional marking will be charged
    $5 per line for Handles or Caps and $10 per line for Rings
  • CUSTOM GAGING – With our vast knowledge, skill set, and experience we can design custom gages tailored for your specific needs. Learn more about custom gaging.
  • No minimum order


Custom Gaging Available (click to enlarge)

Standard Gage Specification

  • All gages are manufactured in accordance with ANSI specification B89.1.6.-2002
  • Roundness and Taper of all Gages will not exceed 50% of the gage maker’s tolerance and are non-accumulative.
  • All Cylindrical gages have edges broken with a .005”-.020” radius or chamfer
  • Unilateral tolerances (one way) on all Go, Nogo, Minimum, or Maximum gages
  • Bilateral (split) on all Master or Set gages
  • Carbide 91-93 Rc
  • Chrome 75-80 Rc
  • Steel 60-62 Rc.

Gage Comparison (click to enlarge)


What Are Ring Gages?

Ring gages are metrology tools that are used for gaging the outer diameters of pins, shafts, splines, fasteners, dowels, studs, and other machined cylindrical parts. These gages are typically cylindrical in shape and are fabricated from a stable material (usually tool steel) with a highly precise (very high-tolerance) bore in their center that functions as the gage for the outer diameter of the parts. The primary function of ring gages is to establish on a go/no-go basis whether the part being gaged falls within the dimensional tolerance that was specified for it. The use of ring gages enables inspections and quality decisions about machined parts to be made very quickly without the need to resort to the use of micrometers, calipers, thickness gages, or other measurement instruments that could take longer to yield a result.

It important to note that ring gages are used to quickly establish if a part falls within the accepted tolerances and yields a yes/no condition based on the gaging. It is not a measurement instrument in the sense that it is not providing an actual value of the part’s diameter – it simple gages whether the part falls within permissible limits and therefore can be accepted from a quality control perspective.

This article will provide information about the types of ring gages, the various configurations that exist, the tolerance sizes, and the uses of these instruments. Note that there is an alternative context of the phrase ring gage which is used in the jewelry industry and refers to tools (also called ring mandrels) that are used to gage the sizes of rings such as wedding bands. These types of gages are not addressed in this article.

To learn more about the other varieties of gages, see our related guide covering the different types of gages.

Photos (click to enlarge)

Types of Ring Gages

There are three primary types of ring gages from the functional perspective:

  • Go ring gages
  • No-go ring gages
  • Master or set ring gages

Go ring gages are designed to verify the upper tolerance limit of the outer diameter of the part. If the go ring gage fits over the outer diameter of the part, then this indicates that the maximum allowable material condition for that part has not been exceeded, meaning that the diameter of the part falls within the upper limit of its tolerance, and therefore, the part is acceptable.

No-go ring gages check the lower tolerance limit on the outer diameter of the part. If the no-go ring gage does not fit over the outer diameter of the part, then this indicates that the minimum allowable material condition for the part has been satisfied, meaning that the diameter of the part exceeds the minimum or lower limit of its tolerance, and therefore, the part is acceptable.

If the go ring gage will not fit over the part being tested, the part diameter is too large, meaning that it contains excess material and should be rejected. Similarly, if the no-go ring gage fits over the part being tested, then too much material has been removed and the part falls below its minimum tolerance value and similarly should be rejected.

When ring gages are used to directly assess the acceptability of parts, the practice is known as direct gaging.

Master ring gages, also called set ring gages, are used for the mastering of other metering instruments. These gages may be used to set other measuring instruments such as bore gages or internal micrometers, for example, by providing a measurement standard or reference standard for calibration purposes. The practice is known as indirect gaging.

Ring Gage Tolerance Classes

Ring gages are available in a variety of tolerance classes. They are typically graded to the following levels, with XXX representing the highest-grade gage that has the tightest tolerances and proceeding to looser tolerances as the grades progress towards ZZ:

  • XXX
  • XX
  • X
  • Y
  • Z
  • ZZ

The applicable standard that establishes these grades is Measurement of Plain External Diameters for use as Master Discs or Cylindrical Plug Gages, B89.1.5 – 1998, published by the American Society of Mechanical Engineers.

The gage tolerance chart that defines the tolerance values as a function of class for different size ranges is shown in Table 1 below. Note that as you proceed from left to right in the table along a given row, the tolerance values increase (moving from class XXX to class ZZ). Also, absolute tolerance values rise with larger values of ring gage sizes.

Ring gage tolerances as a function of tolerance class and ring gage size

Tolerance Chart (English units, Total tolerance)
Ring Gage Size Range (Inches)
Tolerance by Class (micro-inches)
0.010 0.825 10 20 40 70 100 200
0.825 1.510 15 30 60 90 120 240
1.510 2.510 20 40 80 120 160 320
2.510 4.510 25 50 100 150 200 400
4.510 6.510 33 65 130 190 250 500
6.510 9.010 40 80 160 240 320 640
9.010 12.010 50 100 200 300 400 800
12.010 15.010 75 150 300 450 600 1,200
15.010 18.010 100 200 400 600 800 1,600
18.010 21.010 125 250 500 750 1,000 2,000

Ring gage configurations and material options

There are several configurations of ring gage available, which are used for checking different types of parts. Plain ring gages feature a smooth inner diameter and are designed for checking shafts and cylindrical parts that do not have threads or a spline cut along the surface. There are also thread ring gages that are used to verify parts that have been threaded along their outer diameter. These gages will have a corresponding thread cut on the inside diameter of the gage that matches the thread type and pitch on the part. Ring gages are available for all the standard thread types, sizes, and pitches used, including BSPT, NPFT, NPSM, NPT, NPTF, UNC, UNEF, UNF, UNS, and Whitworth.

Within the threaded ring gages, special configurations exist for various types of thread including ACME Thread Ring Gages, Taperpipe Thread Ring Gages, Straight Pipe Thread Ring Gages, ANPT Thread Ring Gages, and Pg Conduit Thread Ring Gages (for use on fittings used in electrical conduit work).

Adjustable ring gages are also available, which contain a set of three slots cut at 120o intervals which enable the gage to be calibrated against a setting plug. This capability reducing production costs by extending the useful life of a gage by permitting one that is no longer within tolerance due to use and wear to be tuned back to tolerance and reused.

There are also miniature thread ring gages available for use in watches and other miniaturized mechanisms.

Ring gage materials are typically tool steel, with options for chrome plated and carbide available that provide for greater wear resistance.

Ring gage data and information credited to:
Source:, All About Ring Gauges – Definition, Sizes, and Uses


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