Thread selection affects fit, tensile stress area, assembly, availability, coating allowance and flange compatibility. A complete B7 fastener order identifies the thread system and class—not only the nominal diameter.
Unified and metric choices
Unified-inch bolting may use UNC or 8-thread-series forms depending on diameter and the applicable flange/fastener standard. Metric products use a stated pitch and tolerance class. Never infer pitch from diameter, especially for replacement studs or international projects.
Thread series
Identify UNC, UNF, 8UN or metric pitch exactly as required. Large-diameter flange bolting often follows a specific thread series defined by the dimensional or piping standard.
Fit and tolerance
State the external thread class and mating internal thread requirement. Coatings can consume allowance, so the coating and gauging sequence must be agreed.
Thread manufacture
Cut and rolled threads can differ in process capability and project acceptance. If thread rolling after heat treatment, grain flow or a particular sequence matters, state it on the purchase order.
Stud length and end configuration
Fully threaded studs, double-end studs and tap-end studs use different length conventions. Chamfers, points, thread lengths and the location from which overall length is measured should follow the named standard or approved drawing. For flange joints, confirm flange rating, gasket, nut height and required thread projection.
Inspection checklist
- Nominal diameter and pitch/threads per inch.
- Thread form, series, class or tolerance and governing standard.
- Overall length convention and threaded-length requirements.
- Gauging condition before and after coating.
- Visual, dimensional and surface-discontinuity acceptance requirements.
- Mating nut grade, thread, coating and lubricant condition.
Use the stud-bolt range, hex-bolt range and weight calculator to continue the selection process, then send the complete joint data for quotation.