Self-Tapping / Thread-Forming Screws
Tapping screws make their own mating thread in sheet metal, plastic or a pre-drilled hole. Type A, AB and B are the common sheet-metal forms; thread-forming and thread-cutting types go into thicker material.
Common types
| Type | Point | Use |
|---|---|---|
| AB | Sharp gimlet | Sheet metal, wood, plastics (replaced Type A) |
| B | Blunt | Heavier sheet, pre-drilled |
| Thread-forming (e.g. Type C) | Blunt, tapered | Displaces metal; no chips |
| Thread-cutting (e.g. Type 23, F) | Cutting flute | Hard or brittle material, castings |
These tables carry the same figures as the printed sheet below.
The printed sheet
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Text version of this sheet
ASME B18.6.3 · self-tapping, thread-forming and thread-cutting screws
FIELD IDENTIFICATION
What it is
Tapping screws make their own mating thread in sheet metal, plastic or a pre-drilled hole. Type A, AB
and B are the common sheet-metal forms; thread-forming and thread-cutting types go into thicker
material.
Sharp point, forms or cuts its own thread
Common types
Type
Point
Use
AB
Sharp gimlet
Sheet metal, wood, plastics (replaced Type A)
B
Blunt
Heavier sheet, pre-drilled
Thread-forming (e.g. Type C)
Blunt, tapered
Displaces metal; no chips
Thread-cutting (e.g. Type 23, F)
Cutting flute
Hard or brittle material, castings
Key points
Pilot hole size decides whether the screw strips or cracks the part. Use the maker chart.
Governing standards: ASME B18.6.3-2023 (covers machine and tapping screws; the former B18.6.4 is now part of it). Editions shown are the latest confirmed as of September 2026.
The drawing and the governing standard always take precedence over this sheet.
torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability
arising from reliance on this reference.
Fastener Guide reference FG-7ACF50 · thefastenerapp.com/fastener-guide/technical-reference/self-tapping-thread-forming-screws · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
