Countersunk Screws Manufacturer in India | Countersunk Tapping Screws

Overview

Countersunk Tapping Screws ISO 7050, 1482 & 14586: Manufacturer & Supplier

A countersunk screw has a 90° cone-shaped head that sits in a countersink, leaving a flush surface with nothing to catch on.

Exotic Alloy manufactures countersunk screws in Mumbai, India, for sheet-metal, enclosure, appliance, HVAC and panel builders. We supply across India and to Bangladesh, South Asia, the Gulf, Africa and Europe. Heads are cold headed and the tapping threads rolled and, for steel, case hardened.

What this page covers

Countersunk tapping screws (ISO 7050 cross recessed, ISO 1482 slotted, ISO 14586 hexalobular) and hexalobular countersunk machine screws (ISO 14581). For other countersunk screws see flat head machine screws (ISO 2009, ISO 7046, inch 82°), hex socket countersunk bolts (ISO 10642) and raised (oval) countersunk heads.

ISO 7050 ISO 1482 ISO 14586 ISO 14581 90° head

Countersunk screw at a glance

Head: 90° countersunk, flush
Tapping: ST2.2–ST9.5, ends C / F / R
Machine: M2–M10 hexalobular (ISO 14581)
Length: Overall, head included
Drives: Cross No. 0–4, slot, T6–T50
Related: Flat head, CSK bolts, oval head

ISO 7050 ST4.8 × 19 countersunk tapping screw, form C, drawn to scale. Thread and recess shown schematically; the length of a countersunk screw is measured overall.

Specification

Countersunk Screw Specification

The range we manufacture and supply.

StandardsISO 7050 (ex DIN 7982); ISO 1482 (ex DIN 7972); ISO 14586; ISO 14581

Size rangeST2.2–ST9.5 (ISO 14586: ST2.9–ST6.3); M2–M10

ThreadTapping screw thread ST (ISO 1478); metric coarse 6g

LengthsOverall length, ISO 7050 commercial lengths 4.5–50 mm

DriveCross (H or Z) No. 0–4; slot; hexalobular T6–T50

Thread endForm C pointed, form F flat, form R rounded (ISO 14586)

MaterialsCase-hardened steel (ISO 2702); A2 / A4 stainless (ISO 3506-4); machine screws 4.8, A2-70, A4-70

FinishZinc plated, zinc flake, phosphated; stainless plain or passivated

CertificationMill certificate; EN 10204 3.1; hardness and torsion test reports

PackingBoxes of 100 to 10,000, bulk cartons

Types

Drives & Thread Ends of Countersunk Screws

One 9.3 mm head, four screws.

Slotted, cross recessed and hexalobular tapping screws and a hexalobular machine screw at the same scale. All four use the same countersunk head and the same countersink.

Standard	Screw	Drive	Sizes	Ends
ISO 7050	Tapping	Cross recess H or Z	ST2.2–ST9.5	C, F
ISO 1482	Tapping	Slot	ST2.2–ST9.5	C, F
ISO 14586	Tapping	Hexalobular T10–T30	ST2.9–ST6.3	C, F, R
ISO 14581	Machine	Hexalobular T6–T50	M2–M10	Metric thread

Dimensions

Countersunk Screw Dimensions

ISO 7050 heads from ST2.2 to ST9.5 at the same scale, from above and in profile.

Size	P	d_k head dia. max / min	k head height max	Cross recess ISO 7050	Slot n × t ISO 1482	Hexalobular ISO 14586	y thread end form C / F	y form R ISO 14586
ST2.2	0.8	3.8 / 3.5	1.1	No. 0	0.5 × 0.4 min	–	2 / 1.6	–
ST2.9	1.1	5.5 / 5.2	1.7	No. 1	0.8 × 0.6 min	T10	2.6 / 2.1	–
ST3.5	1.3	7.3 / 6.9	2.35	No. 2	1 × 0.9 min	T15	3.2 / 2.5	2.7
ST4.2	1.4	8.4 / 8	2.6	No. 2	1.2 × 1 min	T20	3.7 / 2.8	3.2
ST4.8	1.6	9.3 / 8.9	2.8	No. 2	1.2 × 1.1 min	T25	4.3 / 3.2	3.6
ST5.5	1.8	10.3 / 9.9	3	No. 3	1.6 × 1.1 min	T25	5 / 3.6	4.3
ST6.3	1.8	11.3 / 10.9	3.15	No. 3	1.6 × 1.2 min	T30	6 / 3.6	5
ST8	2.1	15.8 / 15.4	4.65	No. 4	2 × 1.8 min	–	7.5 / 4.2	–
ST9.5	2.1	18.3 / 17.8	5.25	No. 4	2.5 × 2 min	–	8 / 4.2	–

ISO 7050 / ISO 1482:2011 and ISO 14586, mm; the three standards share the same head and thread end lengths. y = incomplete thread at the end, max.

Size	T size	A ref lobe width	t recess depth min / max	d_k / k
ST2.9	T10	2.8	0.65 / 0.91	5.5 / 1.7
ST3.5	T15	3.35	1 / 1.3	7.3 / 2.35
ST4.2	T20	3.95	1.14 / 1.58	8.4 / 2.6
ST4.8	T25	4.5	1.39 / 1.78	9.3 / 2.8
ST5.5	T25	4.5	1.65 / 2.03	10.3 / 3
ST6.3	T30	5.6	2.02 / 2.42	11.3 / 3.15

ISO 14586 hexalobular socket countersunk tapping screws, mm.

Size	P	d_k head dia. max	k head height max	Hexalobular T size	b thread length, long screws	Clearance hole ISO 273 medium
M2	0.4	3.8	1.2	T6	25	2.4
M2.5	0.45	4.7	1.5	T8	25	2.9
M3	0.5	5.5	1.65	T10	25	3.4
M3.5	0.6	7.3	2.35	T15	38	3.9
M4	0.7	8.4	2.7	T20	38	4.5
M5	0.8	9.3	2.7	T25	38	5.5
M6	1	11.3	3.3	T30	38	6.6
M8	1.25	15.8	4.65	T45	38	9
M10	1.5	18.3	5	T50	38	11

ISO 14581 hexalobular socket countersunk machine screws, mm; same head as ISO 2009 and ISO 7046. b applies to longer screws; shorter ones are threaded to the head.

Countersinks

One Countersink, and When the Sheet Is Too Thin

The countersink must stop short of the far side. In a 3 mm sheet a land remains under the cone; in a 2 mm sheet the cone runs through and leaves a knife edge.

Every ISO countersunk tapping screw has the same theoretical head diameter as the machine screw it pairs with, so one countersink tool serves both, for example ST4.8 and M5.

A 90° countersink is half as deep as it is wide beyond the hole. When the sheet is thinner than that, use a thicker sheet, a dimpled (formed) countersink, or a raised or pan head.

Tapping screw	Machine screw	Theoretical head D_t, mm	Actual d_k max both	k tapping ISO 7050	k machine ISO 7046 / 14581
ST2.2	M2	4.4	3.8	1.1	1.2
ST2.9	M3	6.3	5.5	1.7	1.65
ST3.5	M3.5	8.2	7.3	2.35	2.35
ST4.2	M4	9.4	8.4	2.6	2.7
ST4.8	M5	10.4	9.3	2.8	2.7
ST6.3	M6	12.6	11.3	3.15	3.3
ST8	M8	17.3	15.8	4.65	4.65
ST9.5	M10	20	18.3	5.25	5

D_t from the ISO machine-screw tables; for tapping screws D_t = d + 2k matches it exactly (our check).

Old DIN vs ISO

DIN 7982 / DIN 7972 vs ISO 7050 / ISO 1482 Heads

The ISO heads are not the old DIN heads. ST3.5 and ST4.2 grew, ST2.2 and ST4.8 to ST6.3 shrank, and only ST2.9 is unchanged.

Size	Old DIN 7982 / 7972 d_k × k	ISO 7050 / 1482 d_k × k	Change d_k / k	Cross recess DIN / ISO
ST2.2	4.3 × 1.3	3.8 × 1.1	-0.5 / -0.20	No. 1 / No. 0
ST2.9	5.5 × 1.7	5.5 × 1.7	+0.0 / +0.00	No. 1 / No. 1
ST3.5	6.8 × 2.1	7.3 × 2.35	+0.5 / +0.25	No. 2 / No. 2
ST3.9	7.5 × 2.3	not in ISO	–	No. 2 / –
ST4.2	8.1 × 2.5	8.4 × 2.6	+0.3 / +0.10	No. 2 / No. 2
ST4.8	9.5 × 3	9.3 × 2.8	-0.2 / -0.20	No. 2 / No. 2
ST5.5	10.8 × 3.4	10.3 × 3	-0.5 / -0.40	No. 3 / No. 3
ST6.3	12.4 × 3.8	11.3 × 3.15	-1.1 / -0.65	No. 3 / No. 3

DIN 7982 / DIN 7972 (1990, withdrawn) and ISO 7050 / ISO 1482 (2011), maximum values, mm. Check old drawings that call up DIN numbers before re-ordering.

Calculator

Countersink & Sheet Thickness Calculator

Pick the screw, enter your sheet thickness and hole diameter, and see the countersink size and depth for a flush head, and the land left under it.

Screw & sheet

Screw size

Sheet thickness, mm

Hole diameter, mm

Our calculation for a 90° countersink cut to the theoretical head diameter D_t: depth = (D_t − hole) ÷ 2; land = sheet − depth. The hole resets to an example clearance hole (ISO 273 medium for M sizes) when you change the size; edit it to suit.

Result

10.4

mm countersink Ø (90°)

2.45

mm countersink depth

Land under the cone:0.55 mm

Head d_k × k:9.3 × 2.8 mm

Thread / pitch:ST4.8 / 1.6 mm

Drive:No. 2 cross / slot / T25

Materials

Countersunk Screw Materials & Finishes

Material	Standard	Finish	Best for
Case-hardened steel	ISO 2702	Zinc plated, zinc flake, phosphated	Steel sheet, HVAC, appliances
A2 stainless (304)	ISO 3506-4 / ISO 3506-1	Plain, passivated	Aluminium, plastics, outdoor panels
A4 stainless (316)	ISO 3506-4 / ISO 3506-1	Plain, passivated	Marine, coastal, food plant
Steel 4.8	ISO 898-1	Zinc plated	ISO 14581 machine screws

Stainless tapping screws suit softer materials; for tapping into steel sheet the case-hardened steel screw is the usual choice.

Carbon steel

Case hardened

Hard surface to form threads.

1018 1022

Stainless A2

304

As in the photo.

304

Stainless A4

316

Chlorides and washdown.

316

Steel 4.8

Machine screws

ISO 14581, zinc plated.

1018

Manufacturing

How Our Countersunk Screws Are Made

1

Wire

Cold heading wire, certified by heat.

2

Cold heading

90° head and recess formed in a two-blow header.

3

Pointing & slotting

End form C, F or R; slots cut.

4

Thread rolling

ST tapping thread or metric 6g.

5

Case hardening

Steel tapping screws, to ISO 2702.

6

Finishing

Zinc, zinc flake or passivation.

Applications

Where Our Countersunk Screws Are Used

Enclosures & panels

Flush covers on sheet-metal cabinets.

HVAC

Ducting, grilles and air handling units.

Appliances

Hinges, trims and plastic housings.

Doors & hardware

Hinges, plates and fittings.

Vehicle bodies

Interior panels and trim strips.

Electronics

Flush machine screws in housings (ISO 14581).

Quality & testing

Countersunk Screw Inspection & Certification

Check	Method	Applied to
Head d_k, k	Callipers, head gauge	Every lot
Recess	Penetration / hexalobular gauges	Every lot
Thread	Ring or profile gauges	Every lot
Surface & core hardness	Vickers / Rockwell, ISO 2702	Steel tapping screws
Torsion & driving test	ISO 2702 / ISO 3506-4	Tapping screws, per lot
Material	PMI / chemical analysis	Stainless lots

Every shipment includes

Mill certificate with heat number
Dimensional report
Lot number on every box

On request

EN 10204 3.1 certificate
Hardness and torsion test reports
Salt spray test for plated lots

FAQ

Countersunk Screw Questions, Answered

A screw with a 90 degree cone-shaped head that sits in a countersink, so its top is flush with the surface. Metric countersunk heads are standardised for machine screws (ISO 2009 slotted, ISO 7046 cross recessed, ISO 14581 hexalobular, ISO 10642 hex socket) and for tapping screws (ISO 1482 slotted, ISO 7050 cross recessed, ISO 14586 hexalobular).

A countersunk screw with a coarse tapping thread that forms its own thread in sheet metal or plastic. ISO 7050 and ISO 1482 cover sizes ST2.2 to ST9.5 and ISO 14586 covers ST2.9 to ST6.3; an ST4.8 screw has a 1.6 mm pitch and a 9.3 mm head.

Yes, for the paired sizes. ST4.8 and M5 have the same theoretical head diameter, 10.4 mm, and the same 9.3 mm actual head, so one 90 degree countersink suits both. The same holds for ST2.2 and M2, ST2.9 and M3, ST3.5 and M3.5, ST4.2 and M4, ST6.3 and M6, ST8 and M8, and ST9.5 and M10. Head heights differ by up to 0.25 mm because the shank diameters differ.

Form C has a pointed end, form F a flat end and form R a rounded end (ISO 14586 only). The incomplete thread at the end, y, differs: on an ST4.8 it is up to 4.3 mm for form C, 3.2 mm for form F and 3.6 mm for form R, which matters in short engagements.

Overall, from the top of the head to the end of the screw, because the countersunk head finishes level with the surface. Pan and cheese head screws are measured from under the head.

Thicker than the countersink is deep. For an ST4.8 countersunk to its 10.4 mm theoretical head diameter over a 5.5 mm hole, the countersink is 2.45 mm deep, so a thinner sheet is left with a knife edge and little support. Then use a thicker sheet, a dimpled (formed) countersink, or a raised or pan head. Our calculator works it out for every size.

DIN 7982 (cross recessed) and DIN 7972 (slotted) were replaced by ISO 7050 and ISO 1482, and the heads changed: ST6.3 went from 12.4 × 3.8 mm to 11.3 × 3.15 mm, ST4.2 from 8.1 × 2.5 mm to 8.4 × 2.6 mm, and size ST3.9 was dropped. A countersink cut for the old head will not always fit the new one flush.

Tapping screws in case-hardened carbon steel to ISO 2702, zinc plated or phosphated, and in A2 or A4 stainless steel to ISO 3506-4. Countersunk machine screws in steel 4.8 and stainless A2-70 or A4-70, like the stainless screws in our photo.