ASME B18.6.3 UNC Slotted 82° Flat Countersunk Machine Screws

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 (ASME B18.6.3 UNC Slotted 82° Flat Countersunk Machine Screws) 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 10,000 pieces. Stock items run 3–7 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.

82° or 90° countersink — why does the angle matter across series?

Inch-series flat head machine screws seat in an 82° countersink; metric flat head screws per DIN 963/ISO 2009 seat in 90°. The head forms look alike, but the cones are not interchangeable — an 82° head in a 90° seat touches only at its outer edge and sits proud or rocks, and the reverse gouges the seat. Match the countersink tool to the screw series, and state the series explicitly when a drawing mixes inch hardware with metric tooling. The ASME B18.6.3 countersunk head designations and the 82° angle go together throughout the standard.

What does the undercut column in the table mean?

For each gauge size the ASME B18.6.3 countersunk table lists the length at or below which the screw is supplied undercut: the underside of the head is relieved so the thread runs up close against it, letting very short screws grip over nearly their full length in thin material — 3/16 in at #4, 5/16 in at #10, 7/16 in at 1/4, 9/16 in at 3/8. Longer screws carry a full shank between thread and head. If your joint is thin and you need maximum thread engagement at short length, ask for the undercut form explicitly on the RFQ.

Why does the table quote only selected sizes?

Every figure above is quoted verbatim from the collected ASME B18.6.3 table at sizes where the dimension columns are complete and consistent. A few cells elsewhere in the collected source carry transcription artefacts (for example a head-diameter maximum printed with a stray leading digit), so this page does not reproduce those cells rather than guess between them. Sizes not quoted are standard ASME B18.6.3 parts and are confirmed dimension-for-dimension against the standard table at quotation.

What is the MOQ and lead time for these inch machine screws?

Minimum order quantity is 10,000 pieces per item. Stocked sizes ship in 3–7 days; non-stock gauge sizes, lengths or finishes are quoted with a confirmed schedule. Common sizes in this designation are widely stocked — confirm the exact schedule against quantity and size mix at quotation.

What should an RFQ for these inch machine screws state?

State the standard designation (ASME B18.6.3 — often still called ANSI B18.6.3), gauge size and threads per inch (for example #4-40, #10-24, 1/4-20 UNC), length and head style, material and grade (steel or stainless; state the stainless grade such as 18-8/A2 or 316/A4 if specified), finish (plain, zinc plated, or other), required certificates such as a mill test report per EN 10204 3.1, and quantity per size — plus destination country.