Bolt Root and Tensile Stress Area

Documents

Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.

Quotation

• The fastener family (Bolt Root and Tensile Stress Area) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
• Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
• Quantity per size and your target delivery date.
• Destination country, and any required documents (for example a mill test certificate) so the quote includes them.

Sample & supply

Minimum order quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at quotation.

Storage & shipping

Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.

Which area should I use for a bolted-joint calculation — root or tensile stress area?

For static pretension and clamp-load calculations, the tensile stress area: it is the standard effective area for a threaded bolt in tension and is what torque-to-preload tables assume. For fatigue assessment, work from the root area, because the root is the stress-concentrated section where cracks initiate — comparing the root area of the threaded section against the full shank area also tells you whether the bolt will yield in the shank or at the threads first. The two columns in this table are roughly 8-10% apart in the metric range (e.g. M 16: 141.0 vs 156.7 mm 2), so using the wrong one shifts a capacity estimate by that much. If the joint is governed by shear, bearing or a code basis (AISC, Eurocode, BS 5950 legacy data on this site), use that code's own areas and rules instead.

Why does the inch table stop changing threads per inch above 1 in.?

Because the tabulated inch series is the coarse 8-UNC thread from 1 in. upward: large-diameter coarse threads keep 8 threads per inch all the way to 4 in., so only the areas grow with diameter (root 0.5509 in 2 at 1 in. against 11.57 in 2 at 4 in.). This matches how stock inch bolts are supplied — an 8-UN thread on large coarse-series sizes. If your joint specifies 8-UN specifically, fine-pitch (UNF) or 8-thread heavy-duty practice, confirm the thread callout on the drawing and quote the size with it; this page carries the tabulated series only, and special pitches are per RFQ.