Countersunk socket head screw (CSK allen screw)

CSK Allen Screws

TVS/Sundaram Fasteners Countersunk Socket Screws

Flush-fitting countersunk socket head screws (CSK allen screws) to DIN 7991 / ISO 10642 for dies, jigs, fixtures and machine guards.

Also calledCSK allen screwCSK boltFlat head allen screwCountersunk allen boltCSK socket screw

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Overview

About our countersunk screws range

Countersunk socket screws sit flush with the surface, making them the standard choice for tooling, moulds, fixtures and anywhere a protruding head would get in the way. We stock TVS/Sundaram Fasteners, Unbrako and LPS CSK screws in alloy steel and stainless steel.

Slotted countersunk screws (DIN 963) and inch CSK screws (BS 2470 / ANSI B18.3) are also available.

Common sizes we supply: M4, M5, M6, M8, M10 and M12 CSK allen screws — for example M6 x 16, M8 x 25 and M10 x 30.

Also known in the trade as: CSK allen screw, CSK bolt, Flat head allen screw, Countersunk allen bolt, CSK socket screw.

Genuine TVS/Sundaram Fasteners (Sundram Fasteners Ltd) M6 x 1 x 25 CSK allen screw countersunk socket screw grade 12.9 box – Perfect Engineering Co, Mumbai — Genuine TVS/Sundaram Fasteners M6 × 25 CSK allen screw, grade 12.9 — original box from our Mumbai stock.

Makes / Suppliers

Available makes

TVS/Sundaram FastenersChennai · Genuine stock

UnbrakoPrecision socket products

LPSLakshmi Precision Screws, Rohtak

Local MakeEconomical everyday grade

Specifications

Technical specifications

Material: Alloy steel · Stainless steel SS 304 / 316
Grade: 10.9, 12.9 · A2-70
Standards: DIN 7991 · ISO 10642 · DIN 963 (slotted) · Inch: ANSI B18.3
Diameter: Metric M3 – M20 · Inch 1/8" – 3/4"
Length: 6 mm – 100 mm

Coatings & Finishes

Finishes available

Black Oxide / Self Colour

Standard heat-treated finish with light oil. Default for high-tensile grades 8.8–12.9.

Zinc Plated – White / Clear

Bright silver electroplate for indoor corrosion protection.

Zinc Flake (Geomet / Dacromet)

Non-electrolytic coating with high corrosion resistance and no hydrogen embrittlement — preferred for 10.9 & 12.9.

Stainless Steel SS 304 (A2)

Natural finish; general corrosion resistance for food, pharma, and outdoor use.

Stainless Steel SS 316 (A4)

Molybdenum grade for marine, chemical, and coastal environments.

Sizes

Countersunk screw size chart (DIN 7991)

Size	Pitch (mm)	Head Dia (mm)	Allen Key (mm)	Typical Lengths
M3	0.5	6	2	6 – 30 mm
M4	0.7	8	2.5	8 – 40 mm
M5	0.8	10	3	8 – 50 mm
M6	1.0	12	4	10 – 60 mm
M8	1.25	16	5	12 – 80 mm
M10	1.5	20	6	16 – 100 mm
M12	1.75	24	8	20 – 100 mm
M16	2.0	30	10	30 – 100 mm
M20	2.5	36	12	40 – 100 mm