Sheet Metal Self-Threading Screws — Types B/BP and BF/BT
Thread dimensions for ANSI sheet-metal self-threading screws: thread-forming types B and BP (major/minor diameter max/min by nominal size 0-0.0600 upward) and thread-cutting types BF and BT — the forms that cut or form their own mating thread in sheet.
Last updated: 2026-11
Specifications
Types B/BP are the workhorse thread-forming forms — BP with a blunter, piercing point — and types BF/BT the thread-cutting forms with chip-cutting flutes; the collected tables print both as major/minor diameter max/min ladders by nominal size, starting at #0-0.0600 (48 tpi): major 0.060/0.054, minor 0.036/0.033, with threads per inch stepping down as sizes grow. The forming vs cutting split is a materials decision the geometry serves: forming forms (B/BP) displace sheet material into the mating thread — strongest formed joint, but they need enough sheet ductility and push force; cutting forms (BF/BT) machine the thread and suit brittle or thick stock where forming forces would distort the part. The tables carry the source's footnote letters attached to the headers (Nominal Sizea, Thds per Inchb, the BTd banner) verbatim — legends live on the collected page. Head styles, lengths, and the type AB/U forms are separate identities; this page is the B-family thread geometry that sets the pilot band in the sheet.
| Thread forming — types B and BP | Sizes #0-0.0600 (48 tpi): major dia. max/min 0.060/0.054, minor dia. max/min 0.036/0.033; ladder continues up through the collected sizes with tpi stepping down — footnote letters on headers carried verbatim |
|---|---|
| Thread cutting — types BF and BT | Same column convention (Nominal Size / Thds-per-Inch / D max-min / d max-min), the cutting forms for brittle or thick sheet; BT banner carries its footnote letter (BTd) as printed |
| Form choice | B/BP form the thread (displacement — max joint strength, needs ductility); BF/BT cut it (chipping flutes — brittle/thick stock, lower drive force) |
| Not tabulated | Type AB/U forms (separate registry identity), pilot-hole charts by sheet material/thickness, lengths and heads — per RFQ |
Materials
- Forming forms need ductile sheet (mild steel, soft aluminum, thermoplastics); cutting forms extend the range to castings, hard sheet and thicker gauge where drive torque would otherwise stall or bulge the part. The geometry on this page is common to steel and stainless screws — corrosion surface and case hardness are order variables, not table variables; quote sheet stack-up (gauge and materials) with the RFQ
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 (Sheet Metal Self-Threading Screws — Types B/BP and BF/BT) 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 does a thread-cutting type (BF/BT) beat a thread-forming type (B/BP)?
When the sheet cannot give. Forming a thread displaces sheet metal, and the forces that make it the strongest joint in ductile steel become the problem in brittle or thick stock: a casting or hardened sheet can crack along the displaced crest, and thick sections raise drive torque until the screw twists off before seating. The BF/BT forms cut chips instead — lower drive force, no work-hardened crest — at the cost of a weaker formed thread (material is removed, not compressed) and chips to manage in the assembly. The collected geometry is deliberately parallel between the two tables (same column convention, same nominal-size ladder) because the size that works is set by the joint; the form is set by the sheet. Pick the form by material and gauge, then hold both tables' major/minor bands against the pilot you actually drill.
The headers carry letters (a, b, d) — are those footnotes I am missing?
They are the collected page's footnote markers, and this transcription carries them verbatim attached to the headers ("Nominal Sizea", "Thds per Inchb", the "BTd" banner) rather than reconstructing the legend, which lives on the source page. On these ANSI tables the letters mark general notes about size designation and threading conventions, not data modifiers — no cell value in the ladder depends on them. The evidence rule this page follows is not to guess at a legend the collected page does not carry: use the numbers as printed, and if a drawing or inspection plan cites a specific footnote text, confirm it against the current ANSI/ASME B18.6.3 sheet before sign-off. The same verbatim policy applies to the repeated banner rows and the max/min stacked headers on this page.
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