Bolt and stud dimensions to the ANSI/ASME B16.5 standard, covering number of bolts, bolt diameter, and stud length by pressure class.
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Dimensions and weights
Dimensional tolerances
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Select a pressure class to view the ANSI/ASME B16.5 bolt and stud dimensions, including number of bolts, bolt diameter, and stud length.
| Nominal Pipe Size (in) | No. Bolts | Bolt Diameter (in) | Stud Length—RF (in) | Stud Length—RJ (in) | Machined Bolt—RF (in) |
|---|---|---|---|---|---|
| 0.5 | 4 | 0.500 | 2.25 | — | 2.00 |
| 0.75 | 4 | 0.500 | 2.50 | — | 2.00 |
| 1 | 4 | 0.500 | 2.50 | 3.00 | 2.25 |
| 1.25 | 4 | 0.500 | 2.75 | 3.25 | 2.25 |
| 1.5 | 4 | 0.500 | 2.75 | 3.25 | 2.50 |
| 2 | 4 | 0.625 | 3.25 | 3.75 | 2.75 |
| 2.5 | 4 | 0.625 | 3.50 | 4.00 | 3.00 |
| 3 | 4 | 0.625 | 3.50 | 4.00 | 3.00 |
| 3.5 | 8 | 0.625 | 3.50 | 4.00 | 3.00 |
| 4 | 8 | 0.625 | 3.50 | 4.00 | 3.00 |
| 5 | 8 | 0.750 | 3.75 | 4.25 | 3.25 |
| 6 | 8 | 0.750 | 4.00 | 4.50 | 3.25 |
| 8 | 8 | 0.750 | 4.25 | 4.75 | 3.50 |
| 10 | 12 | 0.875 | 4.50 | 5.00 | 4.00 |
| 12 | 12 | 0.875 | 4.75 | 5.25 | 4.00 |
| 14 | 12 | 1.000 | 5.25 | 5.75 | 4.50 |
| 16 | 16 | 1.000 | 5.25 | 5.75 | 4.50 |
| 18 | 16 | 1.125 | 5.75 | 6.25 | 5.00 |
| 20 | 20 | 1.125 | 6.25 | 6.75 | 5.50 |
| 22 | 20 | 1.250 | 6.75 | 7.25 | 6.00 |
| 24 | 20 | 1.250 | 6.75 | 7.25 | 6.00 |
We manufacture to your specifications and stock domestic AIS/Buy America and imported materials, with galvanized, epoxy, and additional coatings available. Rubber expansion joints and gaskets are also supplied on request.
A stud bolt is threaded on both ends and fully threaded, and uses two heavy hex nuts, one on each side of the joint; it's the standard choice for most ANSI/ASME B16.5 flange assemblies. A machine bolt has a fixed head on one end and threads only partway up the shank, and is used less often on pressure flanges. This chart lists lengths for both.
ANSI/ASME B16.5 drilling is arranged symmetrically around the bolt circle so the pattern divides evenly into quadrants, which keeps clamping load even and lets the flange bolt up correctly regardless of rotational orientation. That's why every bolt count in this chart, 4, 8, 12, 16, 20, and so on, is a multiple of four.
No. The same bolt count, bolt diameter, and stud length apply whether the flange is slip-on, weld neck, blind, threaded, or socket weld, for a given size and class. Only the stud length facing (raised face versus ring joint) changes the number, not the flange type.
ANSI/ASME B16.5 covers flanges from NPS ½ inch through 24 inch in seven pressure classes: 150, 300, 400, 600, 900, 1500, and 2500.
API International stocks the flanges you need for your project, and our machine shop can modify stock products for special requirements. Contact API International’s experienced sales team, and we will help you select the right flange for your application.
