The difference between gage classes:
The class of a gage refers to the tolerance which is allowed in the manufacturing process of the gage itself. A Class XX gage has an extremely tight tolerance for use in high precision applications, while Class ZZ gages have a lower tolerance and are more suitable for general purpose applications, with Class X thru Class Z falling between each of the aforementioned classes. With a range of tolerances available, it is critical to calculate the tolerance your application will require prior to selecting the class of the gage you use. Scroll down for tolerance table & link to downloadable guide.
Class XX Gages:
These gages have an inch tolerance of .000020" and a metric tolerance of .00051mm. They are one half of the deviation of the X. Ideal for high precision applications where tolerances are critical. (Note: tolerances vary as the diameter range changes, please see the Tolerance Table below for tolerance listings from .010" thru 12.010" and .254mm thru 305.05mm.
Class X Gages:
These gages are available with an inch tolerance of .000040"and a metric tolerance of .00102mm. These gages are used where greater precision is needed. (Note: tolerances vary as the diameter range changes, please see the Tolerance Table below for tolerance listings from .010" thru 12.010" and .254mm thru 305.05mm. See our website for Class X Pin Gages
Class Y Gages:
These gages are available with an inch tolerance of .000070" and a metric tolerance of .00178mm. These gages are used where moderate precision is needed. (Note: tolerances vary as the diameter range changes, please see the Tolerance Table below for tolerance listings from .010" thru 12.010" and .254mm thru 305.05mm.
Class Z Gages:
Class Z gages have an inch tolerance of .0001″ and a metric tolerance of .00245mm. They are one half the deviation of the ZZ for a better fit. (Note: tolerances vary as the diameter range changes, please see the Tolerance Table below for tolerance listings from .010" thru 12.010" and .254mm thru 305.05mm.
Class ZZ Gages:
These gages have an inch tolerance of .0002" and a metric tolerance of .00508mm. They are practical where good precision and speed are important. (Note: tolerances vary as the diameter range changes, please see the Tolerance Table below for tolerance listings from .010" thru 12.010" and .254mm thru 305.05mm. See our website for Class ZZ Pin Gages & Sets
ToleranceS:
DIAMETER TOLERANCE CHART (PER ANSI/ASME B89.1.5)
|
Diameter Range |
"XX" |
"X" |
"Y" |
"Z" |
"ZZ" |
|
Above - Including |
INCH |
||||
|
.010" - .825" |
.000020" |
.000040" |
.000070" |
.0001" |
.0002" |
|
.825" - 1.510" |
.000030" |
.000060" |
.000090" |
.00012" |
.00024" |
|
1.510" - 2.510" |
.000040" |
.000080" |
.00012" |
.00016" |
.00032" |
|
2.510" - 4.510" |
.000050" |
.0001" |
.00015" |
.0002" |
.0004" |
|
4.510" - 6.510" |
.000065" |
.00013" |
.00019" |
.00025" |
.0005" |
|
6.510" - 9.010" |
.000080" |
.00016" |
.00024" |
.00032" |
.00064" |
|
9.010" - 12.010" |
.0001" |
.0002" |
.0003" |
.0004" |
.0008" |
|
Above - Including |
|
|
METRIC |
|
|
|
.254mm - 20.96mm |
.00051mm |
.00102mm |
.00178mm |
.00254mm |
.00508mm |
|
20.96mm - 38.35mm |
.00076mm |
.00152mm |
.00229mm |
.00305mm |
.00610mm |
|
38.35mm - 63.75mm |
.00102mm |
.00203mm |
.00305mm |
.00406mm |
.00813mm |
|
63.75mm - 114.55mm |
.00127mm |
.00254mm |
.00381mm |
.00508mm |
.01016mm |
|
114.55mm - 165.35mm |
.00165mm |
.00330mm |
.00483mm |
.00635mm |
.01270mm |
|
165.35mm - 228.85mm |
.00203mm |
.00406mm |
.00610mm |
.00813mm |
.01626mm |
|
228.85mm - 305.05mm |
.00254mm |
.00508mm |
.00762mm |
.01016mm |
.02032mm |
WAnt to learn more about Precision Gaging?
Download the Gaging Fundamentals Guide to learn the basics of precision gaging and secure essential reference materials including:
- The types of gages.
- The differences between each gage class.
- Gage tolerance selection.
- How to calculate gage tolerance.
- Gage tolerance charts.
- Proper gage maintenance.
