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Flanges & valves › Bevel & counterbore

Weld bevel & counterbore calculator

For guidance only. Always verify against the current edition of the applicable standard and the purchase spec before machining pressure-containing parts.

Works out how far back to machine a butt-weld bevel, and checks how far you can counterbore before the wall gets too thin.

Need the OD at the bevel, the bevel and root-face tolerances or the compound-bevel rule for a given size? See the butt-weld end table (valves and flanges, ASME B16.34 / B16.25).

Bevel

Counterbore (optional)

The minimum wall comes from the design calculation or the purchase spec, not from this page.

How it works, guides and notes

How it works

The bevel is a sloping cut on the pipe end that makes a V-groove for the weld. The calculator works out how wide that slope is at the outside, so you can set your tool or check the bevel with a rule.

Setback = (t − root face) × tan(bevel angle). For a compound bevel, the main angle runs to 19 mm (¾") from the bore and 10° above that, giving setback = (19 − root face)·tan α + (t − 19)·tan 10°. The tolerance band uses 37.5° ±2.5° and root face 1.6 ±0.8 mm (1/16" ±1/32"). Maximum counterbore = OD − 2 × minimum wall. The internal taper is shown at 1:4 and 30°, the usual limits for joining unequal bores.

Sources for the typical figures: ESCO Tool, pipe weld preparation guide; Wermac, unequal wall thickness. The governing figures are in ASME B16.25 and your welding procedure specification (WPS).

This page does geometry only. It doesn’t replace a qualified WPS, the applicable code or an engineer’s sign-off. LatheCalculator accepts no liability for parts machined using it.

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