Flange Dimensions

Flange sizes will vary depending on how they will beflange used. Some of the more common specifications are listed below.

Common Sizes

A flange is measured by taking the maximum ID (inside diameter), OD (outer diameter), bolt circle, bolt hole, bolt size and number of bolts and clamps. An NW 16 CF/Mini has an ID of 0.630 and OD of 1.33. Its bolt circle is 1.063 and has a bolt hole of 0.169. The bolts are 6. It doesn’t need any clamps and has a bolt size of 832 x ¾ (#).

The NW 25 CF/2 ½” has an ID of 0.88 and an OD of 2.11. The bolt circle and hole measure 1.625 and 0.265 respectively. The number of bolts is 4 and no clamps are needed for this flange size. Its bolt size is ¼-28 x 1 1/4 (#).

An NW 35 CF/2 3/4" has an ID and OD of 1.500 and 2.75. The bolt measurements are 2.75, 2.312 and 0.262. Bolts are 6 and the bolt diameter is 1/4-28 x 1 1/4 (#). It doesn’t need any clamps either.

The NW 50 CF/3 3/8" has the following dimensions: 1.88 and 3.37 (ID and OD); the bolt circle and hole measure 2.850 and 0.332. Required bolts are 8 with a bolt size of 5/16-24 x 2 (#). The 1.5" ASA has dimensions of 2.200, 5.00, 3.875 and 0.62. The bolts are 4 (no clamps needed). The bolt size is 1/2-13 x 1 ½.

Other Flange Sizes

The NW 63 ISO-Bolt Flange has an ID and OD of 2.37 and 5.12. The bolt circle and hole are 4.331 and M8. The number of bolts and clamps are 4. The bolt size is M8 x 40. The NW 63 CF/4 1/2" has ID and OD dimensions of 2.500 and 4.47. The bolt circle and hole measure 3.628 and 0.332. The bolt number is 8. The bolt size is 5/16-24 x 2 (#). It does not need clamps.

The NW 80 ISO-Bolt Flange measures 2.87 and 5.71 (ID and OD). The bolt circle and hole are 4.920 and M8. Bolts and clamps needed are 4 each. The bolt size is M8 x 40.


There are a lot of flange sizes because they are used in various ways. Usually the flange is used for support or as a guide. In the case of the former it is used as the flange of a beam (I or T beam). For the latter it is used as a flange for a train wheel. It can also be used to link to a pipe. The flange can also be used to join up to a camera lens.

Flange is also used when constructing pipes. The plumbing fittings are also known flanges. Some flanges are placed above hot water tanks to allow for level flow of water. The flanges used in piping are now standardized.

Knowing the exact flange size is necessary for any project to be successful. If you are going to use these devices ensure you get the appropriate one for the task.

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