Sheet Metal Thread Dimensions (Type AB and Type U Tapping Screws)
Thread-form dimensions for ANSI type AB thread-forming tapping screws (formerly type BA) — major/minor diameter by screw size 0 through the ladder — and type U metallic drive screws: starts, outside and pilot diameters.
Last updated: 2026-11
Specifications
Tapping screws form their own mating thread, so the screw's thread geometry is the hole specification: too big a pilot and the formed thread is weak, too small and the screw stalls or the sheet tears. The collected tables give the two numbers that set it. Type AB (the current designation of the old type BA, and the most common thread-forming form): screw sizes #0 (0.0600) through the ladder with threads per inch from 48 down, major diameter max/min (0.060/0.054 at #0) and minor diameter max/min (0.036/0.033) — the minor pair brackets what the formed thread must grip. Type U metallic drive screws are the hammer-in form: the table prints thread starts (the multiple-start helix that lets them drive straight), outside and pilot diameters in a repeated side-by-side grid as the source lays it out. These are the ANSI thread-form tables behind the DIN/ISO tapping-screw product dimensions registered elsewhere — the head, length and material choices sit on those product pages; this page is the thread-form geometry that sizes the sheet-metal hole.
| Type AB (formerly BA) | Thread-forming tapping screws, sizes #0-0.0600 (48 tpi) up the ladder: major diameter max/min 0.060/0.054 at #0; minor diameter max/min 0.036/0.033 — banner and footnote-letter layout carried verbatim |
|---|---|
| Type U metallic drive screws | Nom. size / number of starts / outside dia. max-min / pilot dia. max-min, grid repeated side by side as printed — the hammer-drive thread form |
| Use | The minor-diameter columns set the pilot/filled-hole band for the formed thread; the major columns set clearance and engagement checks in the sheet gauge being fastened |
| Not tabulated | Types A/B/BP/BF/BT forms (the companion sheet-metal-self-threading identity), hole preparation by sheet thickness and material, screw lengths and heads — see the companion page or per RFQ |
Materials
- The AB form works in plyable sheet metals and plastics; the U drive form displaces rather than cuts and suits blind, torque-free plugs in soft metals and plastics. Pilot-hole selection depends on the sheet material as much as the screw size — steel, aluminum and sheet modulus each shift the band — so pair this geometry with a tested pilot for the actual gauge/material, and quote non-standard sheets per 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 Thread Dimensions (Type AB and Type U Tapping 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
Type AB replaced type BA — does that change the hole I drill?
No — the AB designation carried the same thread form forward with tightened manufacturing tolerances, and the collected table's geometry is the controlling data either way: at #0, a major diameter of 0.054-0.060 and a minor of 0.033-0.036. The formed thread's engagement is set against the minor diameter (the crest of the formed thread fills against the screw's minor), and the practical band is set by sheet thickness and material ductility — a soft aluminum sheet takes the lower end of the pilot band, springy steel the higher. What did change between BA and AB generations is quality-consistency (major/minor stayed in band across production lots), not the form. Use this table's columns for the hole decision, and treat "BA" on a legacy drawing as "AB" for geometry — but confirm the engagement band on the actual sheet gauge, since the table prints thread geometry, not hole charts.
What is a "metallic drive screw" (type U) and when is it the right choice?
A hammer-in fastener: multiple thread starts on a hard, blunt form that is driven straight into a pilot or unfilled hole with no rotational torque at all — the collected table's "number of starts" column is the tell, since a single-start form would twist rather than drive. It holds by displacement in soft metals and plastics, which makes it the answer for plugs, nameplates and blind locations where a screwdriver cannot reach or torque control is impossible — and the wrong answer anywhere the joint sees vibration or needs removal, because removal typically destroys the formed thread and the screw is not designed to be re-driven. Size it by the pilot-diameter column (the hole it displaces into), not by the outside diameter, and treat retention values as application-test results, not catalogue ratings — the collected page carries geometry only.
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