ASME B18.6.3 Slotted Hex Head Machine Screws (Inch Series)
Slotted hex head machine screws to ASME B18.6.3, inch series #4–3/8 — the machine-screw body with a hex head you can also drive from the slot, with the collected per-size table: width across flats, head height, slot width and depth at max/min.
Last updated: 2026-11
Specifications
The slotted hex head machine screw combines two drives on one head: a hex formed on the head flanks for wrench or nut-driver work, and a slot across the top for a conventional screwdriver where access allows only a blade. That redundancy is the reason to specify it over a plain hex head (no driver when the wrench is out of reach) or a plain slotted head (no torque when the slot is chewed or painted over) — the pattern survives field maintenance better than either single-drive option. The collected table runs #4 through 3/8 and carries, per size, the width across flats A with max/min (0.187/0.181 at #4 rising to 0.562/0.551 at 3/8), head height H, slot width J and slot depth T, all max/min — the four figures that decide wrench fit, head clearance and whether the slot still takes a driver after finishing. Threads run both UNC and UNF at every size — the source prints the pitch pair as one compound cell per size (for example 48 UNF / 40 UNC at #4), so the same head geometry serves either series; name the series on the order. This is the first hex-head pattern in the site's B18.6.3 machine-screw coverage — the round, pan, fillister and truss patterns are on their own pages.
| Pattern | Machine screw with slotted hex head to ASME B18.6.3 — dual drive: hex across flats for wrench/nut-driver, slot for blade driver |
|---|---|
| Size range | #4 through 3/8, seven sizes in the collected ladder; each size available in UNC and UNF (pitch pairs tabulated per size, e.g. 48 UNF / 40 UNC at #4) |
| Tabulated geometry | Per size: width across flats A (max/min), head height H (max/min), slot width J (max/min), slot depth T (max/min) — e.g. 1/4: A 0.375/0.367, H 0.190/0.172, J 0.075/0.064, T 0.101/0.083 |
| Threads / finishes / lengths | UNC and UNF both tabulated; finishes and length ranges are not tabulated by the collected source — per RFQ (state thread series, length and finish with the order) |
| Nominal Size | Thread Pitches (UNF / UNC) | Width Across Flats (A) Max | A Min | Head Height (H) Max | H Min | Slot Width (J) Max | J Min | Slot Depth (T) Max | T Min |
|---|---|---|---|---|---|---|---|---|---|
| #4 · 0.112 in | 48 UNF / 40 UNC | 0.187 | 0.181 | 0.060 | 0.049 | 0.039 | 0.031 | 0.036 | 0.023 |
| #6 · 0.138 in | 40 UNF / 32 UNC | 0.250 | 0.244 | 0.093 | 0.080 | 0.048 | 0.039 | 0.046 | 0.033 |
| #8 · 0.164 in | 36 UNF / 32 UNC | 0.250 | 0.244 | 0.110 | 0.096 | 0.054 | 0.045 | 0.066 | 0.052 |
| #10 · 0.190 in | 32 UNF / 24 UNC | 0.312 | 0.305 | 0.120 | 0.105 | 0.060 | 0.050 | 0.072 | 0.057 |
| 1/4 in | 28 UNF / 20 UNC | 0.375 | 0.367 | 0.190 | 0.172 | 0.075 | 0.064 | 0.101 | 0.083 |
| 5/16 in | 24 UNF / 18 UNC | 0.500 | 0.489 | 0.230 | 0.208 | 0.084 | 0.072 | 0.122 | 0.100 |
| 3/8 in | 24 UNF / 16 UNC | 0.562 | 0.551 | 0.295 | 0.270 | 0.094 | 0.081 | 0.156 | 0.131 |
Materials
- Material and finish specified per RFQ — steel with zinc or black oxide are the common stock finishes for this pattern; name the environment and any tooling constraints (nut-driver sizes on hand) with the order
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 Slotted Hex Head Machine Screws (Inch Series)) 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
When is a slotted hex head the right machine-screw pattern?
Specify it when the assembly will be maintained by people and tooling you cannot control. The pattern's value is drive redundancy: the hex takes a nut driver or wrench for assembly torque (the flats at 1/4 size are 0.375/0.367 — a 3/8 nut driver), while the slot keeps a flat-blade screwdriver usable when the hex corners round off or the head is painted over — the common failure that strands a plain hex-head screw in the field. It earns its place on equipment enclosures, terminal covers, jigs and fixtures — anywhere a stripped drive means machining or drilling the head off. Compare against your other options honestly: for production assembly with controlled torque, a plain hex or a socket head drives faster; for corrosive or painted-over environments, the slot is the fallback that keeps the screw removable. The slot dimensions matter for that fallback — at 1/4 the slot is 0.075/0.064 wide and 0.101/0.083 deep, enough for a driver blade that will not cam out under a painted-in head — and the collected table gives those figures at max/min for all seven sizes so the mating blade can be checked, not guessed.
What is the MOQ and lead time for these screws?
The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common sizes in these designations are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
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