THE ABC'S OF Pin PLUG GAGES, and the 10 percent gauge rule , info and tolerances, class ZZ, Z, Y, X, XX

30 Sep.,2022


Plug Gages

Plug Gage Measuring - the art of using pre-sized precision metal plugs to determine the acceptability of diameters of drilled or machined holes.

The difference between any class of gage is not the wear or life span of the gage, it's the tolerance which is allowed in the manufacturing process of the gage.

GO/NOGO Measurement - A GO gage is used to check the lower limit of a hole.

A NOGO gage is used to check the upper limit of a hole.

If the GO gage enters the hole and the NOGO gage is unable to enter, the design specifications of the hole have been met.


Uses - for precision GO/NOGO measuring of hole sizes and depths, checking hole location and distance, and setting micrometers.

All gages are uniformly 2” long with ground ends, allowing you to use both ends for increased gage life. Gages are Carbon Chrome Alloy Steel (grade 52100 bearing quality steel) and heat treated to a 60-62 Rockwell C hardness.

All of our products come with a Certificate of Class Conformance, traceable to NIST (National Institute for Standards Technology).

The size and “+” (GO) or “-” (NOGO) are laser etched with a Meyer Exclusive Serial Number feature to ensure traceability on your shop floor on all gages that are .061” and larger.

Class ZZ Gages - These gages have an inch tolerance of .0002” and a metric tolerance of .005mm.

They are practical where good precision and speed are important.

Class Z Gages - These gages have an inch tolerance of .0001” and a metric tolerance of .0025mm.

They are one half the deviation of the ZZ for a better fit.

Class X Gages - These gages are available with an inch tolerance of .00004” and a metric tolerance of .001mm.

These gages are used where greater precision is needed.

Class XX Gages - These gages have an inch tolerance of .00002” and a metric tolerance of .0005mm.

They are one half of the deviation of the X.

Great for your most critical needs.

Length and Finish - All gages are 2 inches or 51mm long with ground ends for long life.

52100 Steel - This is bearing quality, Carbon Chrome Alloy Steel, heat treated to 60-62 Rockwell C hardness and is considered the preferred material for the highest quality plug gages.

Certificate of Class Conformance - Assurance issued with each shipment of quality gages that conformance characteristics are traceable to NIST.

NIST - National Institute of Standards and Technology

Serial Number Etching - A feature that is exclusive to Meyer Gages and essential in assuring traceability on the shop floor on all gages over .060”.

Plus Gage Tolerance - plus the tolerance, minus 0.0000

Minus Gage Tolerance - minus the tolerance, plus 0.0000


Gage Makers Tolerance Chart
Plain Plug, Plain Ring & Master Gage Tolerances RANGE CLASS INCH   XX X Y Z ZZ .0009" to .8250" .000020" .000040" .000070" .000100" .000200" .8251" to 1.5100" .000030" .000060" .000090" .000120" .000240" 1.5101" to 2.5100" .000040" .000080" .000120" .000160" .000320" 2.5101" to 4.5100" .000050" .000100" .000150" .000200" .000400" 4.5101" to 6.5100" .000065" .000130" .000190" .000250" .000500" 6.5101" to 9.0100 .000080" .000160" .000240" .000320" .000640" 9.0101" to 12.2600" .000100" .000200" .000300" .000400" .000800" METRIC   XX X Y Z ZZ 1.00mm to 21.00mm .0005mm .0010mm .0018mm .0025mm .0050mm 21.01mm to 38.00mm .0008mm .0015mm .0023mm .0030mm .0060mm 38.01mm to 64.00mm .0010mm .0020mm .0030mm .0040mm .0080mm 64.01mm to 115.00mm .0013mm .0025mm .0038mm .0050mm .0100mm 115.01mm to 165.00mm .0017mm .0033mm .0048mm .0060mm .0130mm 165.01mm to 230.00mm .0020mm .0041mm .0061mm .0080mm .0160mm 230.01mm to 300.00mm .0025mm .0051mm .0076mm .0100mm .0200mm





10% Rule The 10% Rule is intended to assist in the selection of the tolerance for Go & No-Go gages. The premise is; if you surrender 10% of the total product tolerance to the gages, you will pass 90% of your product tolerance 100% of the time, if the Go fits and the No-Go does not. Go Plug Gage Using the minimum diameter of the hole as the Go and applying the tolerance PLUS insures that, if the Go plug goes through the hole, the hole is larger than the the minimum diameter. No-Go plug Gage Using the maximum diameter of the hole as the No-Go and applying the tolerance MINUS insures that, if the No-Go plug does not enter the hole, the hole diameter is smaller than the maximum diameter of the hole and in tolerance.  

See ASME B89.7.3.1 for more information on the 10% Rule and options beyond this rule.



  • Hole Size =.250 +.004"
  • Product Tolerance = .004"
  • .004 x 10% = .0004"
  • .0004 X .5 = .0002"
  • .0002" = Class ZZ Tolerance per ASME B89.1.5 (See Tolerance Chart Above )
  • GO Plug Gage = .250 +.0002" (Suggested)
  • NO-GO Plug Gage = .254 -.0002" (Suggested)



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