1-1/4 inch class 300 flange: dimensions, bolt circle and drilling (ASME B16.5)
The 1-1/4 inch class 300 flange to ASME B16.5 is 5.25 in (133.4 mm) across, with 4 holes of 0.75 in (19.1 mm) on a 3.88 in (98.4 mm) bolt circle, for 5/8 in bolts; the pipe is 1.66 in (42.2 mm) outside. The holes straddle the centre lines, the first one 45° off, and the chord between neighbouring holes, which is the divider setting for stepping the drilling out, is 2.74 in (69.6 mm).
Dimensions
| Outside diameter | 5.25 in (133.4 mm) |
|---|---|
| Bolt circle (PCD) | 3.88 in (98.4 mm) |
| Number of holes | 4 |
| Hole diameter | 0.75 in (19.1 mm) |
| Bolts | 5/8 in |
| Pipe outside diameter | 1.66 in (42.2 mm) |
| Angle between holes | 90° |
| First hole from the centre line | 45° |
| Chord between neighbouring holes | 2.74 in (69.6 mm) |
Draw this flange: 1:1 template and DXF
Hole coordinates
From the centre of the flange, in mm, with the first hole 45° off the horizontal axis and the others counter-clockwise, as the standards lay the drilling out.
| Hole | Angle | x (mm) | y (mm) |
|---|---|---|---|
| 1 | 45° | 34.8 | 34.8 |
| 2 | 135° | -34.8 | 34.8 |
| 3 | 225° | -34.8 | -34.8 |
| 4 | 315° | 34.8 | -34.8 |
Questions
- How many bolts does a %{size} %{class} flange have?
- %{holes}, of %{bolt}, through holes of %{hole} on a %{circle} bolt circle.
- What is the bolt circle of a %{size} %{class} flange?
- %{circle}. The holes are %{angle}° apart, and the first one sits %{half}° off the centre line, so that two flanges mate in any symmetric position. The chord between neighbouring holes is %{chord}.
- Can a %{size} %{class} flange be cut from plate?
- As a plate flange, for low pressure: ducts, tanks, water lines. The outline and the drilling above are what the flange calculator draws, with the 1:1 template and the DXF for plasma or laser. A pressure flange to %{standard} is forged, with a hub and a raised face, and its thickness and facing come from the standard.