Flange Face Surface Finish & Serration Calculator
Calculate arithmetic average roughness Ra (µin & µm), peak-to-valley groove depth Rz, phonographic spiral feed rates, and gasket compatibility per ASME B16.5.
Machining Feed & Tool Geometry
Intended Gasket Specification
Calculated Roughness & Compliance
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
Why does ASME B16.5 specify a 125 to 250 microinch Ra serrated finish?
A perfectly mirror-smooth finish is detrimental for spiral-wound and sheet gaskets because the slick metal provides zero frictional traction, allowing the gasket to squirt outward or blowout under internal pressure. The 125 - 250 µin (3.2 - 6.3 µm) serrations act as mechanical teeth that grip the graphite or PTFE filler, locking it firmly in place.
What is the difference between phonographic spiral and concentric serrations?
A spiral (phonographic) groove is cut in a single continuous lathe feed pass from outer diameter to bore. A concentric serration consists of individual closed concentric circles. While spiral grooves are easier and cheaper to machine, hydrogen or lethal gas services require concentric grooves to eliminate the continuous spiral leak path.
How does tool nose radius directly determine surface roughness Ra?
From metal cutting mechanics, the peak-to-valley height of a round-nosed turning tool is Rz = f² / (8 * r), where f is feed per revolution and r is tool corner radius. Halving the feed rate slashes roughness height by a factor of 4, while doubling the nose radius cuts roughness height in half.