EKINSUN is a custom parts manufacturer that turns tapping screws to drawing when the standard series stops: a length or head outside the range, a thread form for a plastic or an alloy the series was not designed for, a shoulder or a dog point, a material such as 316L, brass or PEEK.
A typical request: countersunk tapping screws for a 12 mm glass-filled nylon boss, where every stock screw either cracks the boss or strips on the second assembly.
Glass-filled plastic is where standard tapping threads stop working and thread-forming screws for plastics begin.
ST sizes, and what the catalogue list calls them
| ST size (ISO 1478) | Sold as | Common standard heads | Typical sheet |
|---|---|---|---|
| ST2.2 | M2 | pan PA, countersunk KA | 0.5–1 mm |
| ST2.9 | M3 | pan, countersunk, truss, pan washer | 0.7–1.5 mm |
| ST3.5 | M3.5 | pan, countersunk | 0.8–2 mm |
| ST3.9 / ST4.2 | M4 | pan, countersunk, truss, hex washer | 1–2.5 mm |
| ST4.8 | M5 | pan, countersunk, hex washer | 1.2–3 mm |
| ST5.5 | M5.5 | hex washer (self-drilling) | 1.5–4 mm |
| ST6.3 | M6 | pan, hex washer, hex | 2–5 mm |
| ST8 | M8 | hex | 3–6 mm |
Standard: pan PA M1–M8, countersunk KA M1–M8, truss TA M2–M6.3, large pan BA M2–M3, thin CA M2–M6, pan washer PWA M1.2–M5, hex washer M3–M6.3, socket-cap HA M1.7–M6, button PCA M2–M6, countersunk socket KCA M2–M6, Torx pan and countersunk M2–M6, in A2 and zinc steel; brass M2–M8. Sheet thicknesses are indicative for steel.
Need self-tapping screws in a size, thread or material no catalogue lists? EKINSUN is a custom parts manufacturer: we make self-tapping screws to your drawing, sketch or sample, steel, 304 or 410 stainless steel, from 1 piece, quoted in 12 hours and shipped duties paid. Already a catalogue size? Ask us too, we may have it in stock, and larger quantities cost less per piece. All custom fasteners
Which screw end for which material
| End | Standard code | Standard | Material | Hole |
|---|---|---|---|---|
| Pointed (type C / AB thread) | A: PA, KA, TA, BA, CA | ISO 1478 type C; ISO 7049 / 7050 / 7051 | thin steel and aluminium sheet, soft plastics, wood | pilot hole or pierced; the point starts the thread |
| Flat end (type F / B thread) | B: PB, KB, TB, CB | ISO 1478 type F | thicker sheet, castings, plastics with a moulded hole | pre-drilled to the maker's table; no point to wander |
| Cutting end (BT / type 25) | T: PT, KT, TT, BT | maker series | thick, hard or brittle: die castings, hard plastics, phenolic | pre-drilled; the slot cuts chips and lowers driving torque |
| Drill point (self-drilling) | — | ISO 15480 (hex washer), 15481 (pan), 15482 (countersunk); DIN 7504 K / N / P | steel and aluminium sheet, purlins, roofing; 410 stainless or zinc steel | no hole; the drill point number sets the thickness it drills |
| Tri-lobular thread-forming | — | DIN 7500 (Taptite-type) | steel, aluminium, brass; rolls a metric thread a machine screw can follow | pilot near the pitch diameter; no chips |
| Thread-forming for thermoplastics (PT-type) | — | maker series | ABS, PC, PA, PBT, glass-filled grades | moulded boss hole; 30° flank and deep thread avoid boss stress |
| Chipboard and drywall | — | DIN 7997; DIN 18182 | wood, particleboard, plasterboard | no pilot in soft board |
| Hardened fibre and concrete nails | — | maker series | masonry, fibreboard | on request, from 1 piece |
What to send for a tapping screw that is not standard
- Material and thickness of what the screw goes into, and whether the hole is pierced, drilled or moulded.
- Screw end: pointed, flat, cutting, drill point or thread-forming; if unsure, send the material and we choose.
- Head: type and diameter, and whether a captive or sealing washer is wanted.
- Length under the head, and the thread length if a plain shank is needed.
- Drive: Phillips, Pozi, Torx, hex socket, hex washer head.
- Material: A2, A4 / 316L, 410 hardened, zinc steel, brass, or a plastic screw; quantity.
A tapping screw with the wrong end is the commonest field failure in plastics: a pointed steel screw in a glass-filled boss cuts the boss instead of forming it. Send the plastic grade and the boss size before the screw size.
Where the tapping screw catalogue stops
| What you need | In the catalogue? | What we make |
|---|---|---|
| Pan, countersunk or truss tapping screw ST2.2–ST6.3 in A2 or zinc steel, standard length | Yes | Buy it from stock, or have it made to order from 1 piece. No one-off competes with a rolled tapping screw. Standard parts: ask us too, we may have them in stock. |
| Self-drilling screw 3.5–6.3 mm in 410 stainless or zinc steel, with or without EPDM washer | Yes | Standard sizes: buy them off the shelf, or have them made to order from 1 piece. Standard parts: ask us too, we may have them in stock. |
| Thread-forming DIN 7500 M3–M6 in pan, countersunk, hex flange, Torx | Yes | Standard in zinc and nickel steel; buy it. |
| A tapping screw longer than the standard lengths, or with a plain shank section | No | Turned from bar with the tapping thread cut to the standard form, from 1 piece. |
| A head diameter or drive the series does not pair with that size | No | Head and recess machined on the turned screw. |
| A tapping screw in 316L, brass above M8, titanium or PEEK | No | Same thread form, your material; PEEK tapping screws for insulating assemblies. |
| A thread-forming screw for a glass-filled plastic in a size the PT series does not run | No | Turned with the 30° flank form to the boss. |
| A tapping screw in aluminium 6061 or 7075 | No | Not offered: an aluminium tapping thread strips in anything harder than soft plastic, and we say so; use a 7075 machine screw in an insert instead. |
Materials
| Material | Designation | Where it fits here |
|---|---|---|
| Stainless 304 | 1.4301 / A2 | standard tapping screws in every head; not self-drilling (too soft to drill) |
| Stainless 410, hardened | 1.4006 | standard self-drilling screws 3.5–6.3 mm |
| Stainless 316L | 1.4404 / A4 | turned to order for marine and chemical assemblies |
| Carbon steel, case-hardened | zinc, nickel, phosphate | standard tapping, self-drilling, chipboard and drywall screws |
| Brass | CW614N / CuZn37 | standard M2–M8 tapping screws; turned above |
| PEEK, nylon 66 | PEEK, PA66 | insulating tapping screws, see plastic fasteners |
| Aluminium 6061 | AlMg1SiCu | the sheet the screw goes into, not the screw |
| Aluminium 7075 | AlZn5.5MgCu | machine screws into inserts, not tapping screws |
Related pages
- the nut, bolt, washer and pin chart, all families with standard and size range
- pan, cheese and countersunk heads, head and drive types chart
- heat-set and press-in inserts, when a tapping screw is the wrong answer in plastic
- screws with captive washers, tapping screws with captive washers
- pin-Torx and tri-head screws, pin-Torx tapping screws
- clinch fasteners for sheet metal, a permanent thread in thin sheet
- Custom plastic parts, the moulded boss the screw goes into
Frequently asked questions
AB (ISO 1478 type C) has a pointed end and a fine spaced thread for thin sheet; B (type F) has a flat end for pre-drilled holes in thicker material; BT (type 25) is a B thread with a cutting slot at the tip for thick, hard or brittle material. Catalogue lists mark them A, B and T after the head letter.
ST is the ISO 1478 tapping-screw thread designation and 4.2 is the nominal diameter in millimetres; catalogue lists usually print it as M4. ST2.9 is sold as M3, ST4.8 as M5, ST6.3 as M6.
Yes, but the end and thread form must suit the plastic: pointed screws work in soft ABS and PP, while glass-filled nylon, PBT and PC need thread-forming screws with a 30-degree flank (PT-type) so the boss is not cracked. For repeated assembly, a threaded insert is the durable answer.
Because the drill point has to be harder than the steel it drills, and 410 can be hardened while 304 cannot. 410 is less corrosion-resistant than 304, so standard self-drilling screws for outdoor use are often zinc-coated 410 or carbon steel with a zinc-flake finish.
EKINSUN is a custom parts manufacturer that turns tapping, thread-forming and drill-point screws in 304, 316L and 410 stainless, steel, brass and PEEK, with the length, head, drive and thread form the assembly needs, from 1 piece, with a quote within 12 hours.
No list price; the drivers are material, the thread form, head and drive machining, and quantity. A batch of A2 tapping screws in an odd length is a short lathe job; a single PEEK thread-forming screw for a glass-filled boss is a small precision part and priced as one. The quote names the drivers.
Send the material it goes into
Material and thickness of the part, hole type, screw end, head and drive, length, screw material, quantity. A photo of the boss or sheet with a rule works. From 1 piece, quote within 12 hours.