ASME B18.6.3 UNC Slotted Pan Head Machine Screws
Slotted pan head machine screws per ASME B18.6.3, UNC thread — gauge 0000 through 3/4 in basic diameter in steel or stainless steel. The low, wide domed head with a flat top: the general-purpose slotted head of inch-series small machinery and consumer electronics.
Last updated: 2026-11
Specifications
The pan head is the workhorse slotted head of the inch series: lower and wider than the traditional round head, with a flat top and a generous bearing circle, designed to be driven by a flat blade in assemblies that do not need high-torque drives. The collected ASME B18.6.3 table covers the full machine screw gauge range from 0000 up to 3/4 in basic diameter on UNC threads. At #4 the head measures 0.219 in maximum diameter by 0.068 in maximum height with a 0.042 in head edge radius; at 1/4 it grows to 0.492 in by 0.144 in — roughly one diameter across, the proportion that makes pan heads predictable to design around. Compared with its metric counterpart DIN 7985 (cross recessed pan head), the head form is the same idea with a single slot; the slotted round head is the taller, narrower member of the same lineage.
| Standard | ASME B18.6.3 — slotted pan head machine screws, UNC (unified coarse) thread |
|---|---|
| Size range | Gauge 0000 – 3/4 in basic diameter, UNC threads per inch |
| Dimensions at #4 (#4-40) | dk (head diameter) max 0.219 in (min 0.205 in); k (head height) max 0.068 in (min 0.058 in); r (head edge radius) 0.042 in; slot width n 0.039–0.031 in; slot depth t 0.040–0.030 in |
| Dimensions at #10 (#10-24) | dk max 0.373 in (min 0.357 in); k max 0.110 in (min 0.099 in); r 0.061 in; slot width n 0.060–0.050 in; slot depth t 0.068–0.053 in |
| Dimensions at 1/4 (1/4-20) | dk max 0.492 in (min 0.473 in); k max 0.144 in (min 0.130 in); r 0.087 in; slot width n 0.075–0.064 in; slot depth t 0.087–0.070 in |
| Materials | Steel, stainless steel — grade and finish confirmed at quotation (tenant supply range) |
Materials
- Steel
- Stainless steel
Ordering & documentation
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 Pan Head 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.
Frequently asked questions
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 minimum printed off the size progression), 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.
Pan head slotted or cross recessed — which drive for the same head?
The pan head geometry exists in both drives: the slotted version here takes a flat blade, while cross recessed pan head screws (the DIN 7985 form on the metric side) centre a Phillips driver and resist cam-out under powered assembly. The head dimensions are close enough that the choice usually follows the tooling on the line: hand service with a flat blade favours the slot, production driving favours the recess. State the drive explicitly on the RFQ — a slotted callout filled with Phillips drivers is the classic bench error.
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.
Related knowledge
- Thread-Forming vs Thread-Cutting vs Thread-Rolling Self-Tapping Screws: What the Evidence Settles on Base Material
- Screw Family Selection by Base Material: Wood, Machine and Self-Tapping Threads, Engagement and Coating
- Hex Bolts vs Socket Head Cap Screws: What the Evidence Settles on Strength, Clearance and Cost
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support