Unified Tap Drill Chart — UNC / UNEF / UNF Reference, #0-80 to 1-3/4-5, inch

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 (Unified Tap Drill Chart — UNC / UNEF / UNF Reference, #0-80 to 1-3/4-5, inch) 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.

The same 1/4 in size appears at 20, 28 and 32 TPI with three different drills — how should I read this chart and what decides the drill finally used?

The drill is a function of the whole thread callout, which is why the chart lists every TPI as its own row: 1/4-20 UNC takes a #7 (0.201 in), 1/4-28 UNF a #3 (0.213 in), 1/4-32 UNEF a 7/32 (0.2188 in) — finer pitch leaves more minor-diameter room, so the hole grows as threads per inch rise on the same nominal. Reading the chart is therefore always: find the exact thread designation, take the drill, verify the decimal, and remember the major-diameter column is what the finished thread should measure outside, useful as a sanity check after tapping. What finally decides the drill on the shop floor is the tolerance window those decimals imply: drills wear and run oversize, so a production shop checks the first holes against the internal minor-diameter limits of the thread class — the modern selection basis this chart follows — rather than trusting the nominal drill to hit the window forever. For long engagement, the FED-STD-H28/2B-1991 banding (cited in the source) shifts the target hole upward toward the maximum to reduce tap torque; for short engagement it tightens toward the minimum for thread height. Two flagged rows (1-1/16-18 and 1-9/16-18 UNEF) print improbable drill tokens in the source; use their decimal columns. If you need a reamed hole to hold 3B reliably, that is a process call — per RFQ.

What is the MOQ and lead time for threaded parts and tooling referenced by this chart?

The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Confirm the exact schedule against quantity, size mix and any tooling items at quotation.