Tapping screws type 1 and 2, and trilobular thread-forming screws — point, use and how to choose
Sharp point is type 1, blunt point is type 2, and a rounded-triangle cross-section is a trilobular thread-forming screw (often called TAPTITE). Choose by base material and pilot hole, then confirm with a trial.
A tapping screw forms its own mating thread as it is driven. A machine screw needs a tapped hole or a nut; a tapping screw goes into a pilot hole or thin sheet and cuts or forms the thread itself, which removes tapping and nuts from the assembly line.
The most common mix-up on the shop floor is ordering type 1 when type 2 was needed, or the reverse. Head and size look identical on a drawing, but the point and thread differ, and so does the material they suit. Trilobular thread-forming screws, often called by the trade name TAPTITE, work on a different principle altogether.
Type 1, type 2 and trilobular screws at a glance
| Type 1 | Type 2 | Trilobular thread-forming (B, C) | |
|---|---|---|---|
| Point | Sharp | Blunt (flat end) | Blunt |
| Cross-section | Round | Round | Rounded triangle (trilobular) |
| How the thread is made | Cut | Cut (slotted point) | Rolled / formed — almost no chips |
| Thread spacing | Wide (coarse) | Closer than type 1 | B: like type 2 · C: same as machine screw |
| Pilot hole | Optional in thin or soft material | Required | Required |
| Suited to | Thin steel sheet, sheet metal, wood, plastic | Pre-punched sheet, non-ferrous metal, thicker sheet, plastic | Aluminium die-casting, mild sheet, electrical and battery housings |
| Rough overseas equivalent | Type A | Type B | Thread forming (trilobular) |
| Our stock | 471 items | 196 items (all slotted) | 54 items (M3, M4 · B 42, C 12) |
"Equivalent" means similar use, not identical dimensions. When converting an overseas drawing, check size and pitch separately.
Type 1 and type 2 are classes of the KS B 1032 annex. The main body of KS B 1032 follows ISO, with ST2.9, ST3.5, ST4.2 designations and different dimensions; type 1, type 2 and M3/M4 sizes sit in the annex (the former main body). Most tapping screws made in Korea follow the annex, and our type 1 and type 2 follow the annex. If your drawing specifies ST sizes, tell us when requesting a quote.
Type 1 has a sharp point and bites in on its own. In thin sheet or plastic it can go in without a pilot hole; in thicker steel a pilot hole is recommended.
Type 2 has a blunt point, so it relies on an existing hole. The closer thread grips well in thicker material, and the blunt point is safer where it protrudes through the part.
Type 2 slotted and unslotted
A type 2 screw with a small slot at the point is called slotted (cutting); one without is unslotted. The slot acts as a cutting edge and lowers driving torque; the unslotted type relies more on forming.
All 196 type 2 items in our catalog are slotted — shown as "Type 2 (cutting)" in the Point row of each product page. Unslotted type 2 is made to order.
Trilobular screws are not tapping screws
What the shop floor often calls "TAPTITE" — a registered trademark of REMINC — is, generically, a thread-forming screw with a rounded-triangular (trilobular) cross-section. It rolls the thread instead of cutting it, so it produces almost no chips and the formed thread resists vibration loosening.
- Type B — pitch and use similar to type 2 tapping screws. Aluminium die-casting, non-ferrous metals, electrical parts sensitive to loosening.
- Type C — same pitch as a metric machine screw. Form the thread with the trilobular screw first; in service, a standard machine screw of the same size can replace it. Used in electrical housings and battery packs where chips are not acceptable.
We stock case-hardened carbon steel trilobular thread-forming screws in M3 and M4, both type B and type C (pan head; zinc, coloured or nickel plated). The last letter of the part number, B or C, shows the type.
Material decides the base it suits
| Material | Heat treatment | Our stock (type 1, 2) | Notes |
|---|---|---|---|
| Carbon steel (10A) | Case hardened (except some small and long sizes) | 420 items | Hard surface forms threads in steel sheet. Used with zinc or nickel plating against rust |
| Stainless A2 (STS304Cu) | None | 255 items | Corrosion resistant. Cannot be hardened, so results vary against hard mating material |
Case hardening gives carbon steel tapping screws a hard skin, so their own thread survives while forming one in steel sheet. Heat treatment is shown per part number in the "Heat treatment" row of each product page.
Austenitic stainless steel cannot be hardened by quenching. It is the choice where rust is not acceptable, but in thick or hard mating material its thread may fail first, so it should be confirmed against the actual part.
Why we don't publish a pilot-hole table
The question we hear most is "what pilot hole diameter should I use?" We deliberately do not give a single table. For the same M4 screw the right hole depends on whether the part is cold-rolled sheet or aluminium die-casting, on its thickness, and on whether the hole is punched or drilled. Without knowing the mating material and hole condition, one number presented as the answer does more harm than good.
The reliable way is a trial on the actual part. If driving torque is too high or the thread strips, enlarge the hole slightly; if it spins or grips weakly, reduce it. Before production, request samples through Quote & samples and test them.
How to choose
- Base material — thin sheet, wood or plastic: type 1. Thicker sheet, non-ferrous or pre-punched: type 2.
- Pilot hole — none: type 1. Existing hole: type 2 grips better.
- Chips — where chips are not allowed (electrical, battery): trilobular thread-forming screw.
- Re-assembly — frequent service: trilobular type C, replaceable with a machine screw.
- Corrosion — outdoor or wet: stainless; against hard material: case-hardened carbon steel with plating.
- Confirm by trial — pilot hole and driving torque are set on the actual part.
For driver bits see cross-recess driver bits; for thread engagement see engagement depth.
Tapping screws in our catalog
| Type | Stock | Browse |
|---|---|---|
| Type 1 | 471 items | Type 1 list |
| Type 2 (slotted) | 196 items | Type 2 list |
| Trilobular B, C | 54 items | Trilobular list |
| Sizes | M2 – M6 (M4 most common), inch 5/32 | |
| Heads | Pan · flat (countersunk) · truss · pan with washer face | |
| Finish | Plain · clear zinc · white zinc · nickel · coloured · passivated | |
Every item has a 3D model and drawing, so fit and engagement length can be checked at the design stage. Type 1 and type 2 follow the KS B 1032 annex.
TAPTITE® is a registered trademark of REMINC (Research Engineering & Manufacturing Inc.). Our thread-forming screws are our own manufacture and are not genuine or licensed TAPTITE® products.
FAQ
What is the difference between type 1 and type 2 tapping screws?
Point and thread. Type 1 has a sharp point and coarse thread and bites into thin sheet, wood or plastic by itself. Type 2 has a blunt point and closer thread, goes into a pre-made hole, and suits thicker sheet and non-ferrous metal.
What is a slotted (cutting) type 2 screw?
A type 2 screw with a small slot at the point that helps cut the thread and lowers driving torque. All type 2 items in our catalog are slotted; unslotted type 2 is made to order.
Is TAPTITE the same as a tapping screw?
No. What is often called TAPTITE (a registered trademark of REMINC) is a trilobular thread-forming screw that rolls the thread instead of cutting it, so it makes almost no chips and resists loosening. Type C has machine-screw pitch and can be replaced by a machine screw in service. We stock carbon steel M3 and M4 trilobular screws in types B and C.
What pilot hole should I use for a tapping screw?
It depends on the mating material, its thickness and how the hole is made, so there is no single answer. Test on the actual part: enlarge the hole if torque is too high, reduce it if grip is weak. We recommend testing samples before production.