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Socket Screws Supplier in India: Types, Standards, Size Charts, Materials & Grades
Socket Screws: Types, ISO/DIN Standards, Size Charts, Materials & Grades
Socket (Allen) screws deliver high torque in compact spaces, making them essential in machinery, tooling, robotics, and automotive assemblies. This guide covers common types, ISO/DIN standards, practical size charts, materials, and grades.
Shop: Socket Head Cap Screws • Flat Head Socket (CSK) • Socket Grub/ Set Screws • Socket Button Head Screws • Flange Button Head Socket Screws • Low Head Socket Cap Screws • Socket Head Shoulder Screws
Types of Socket Screws (with ISO/DIN)
- Socket Head Cap Screws — ISO 4762 (≙ DIN 912): high-strength general purpose.
- Flat Head / CSK Socket Cap — ISO 10642 (≙ DIN 7991): flush surface.
- Socket Grub / Set Screws — ISO 4026/27/28/29 (DIN 913/914/915/916): headless positioning/locking.
- Socket Button Head — ISO 7380-1: smooth, low-snag head.
- CSK Socket Head Cap Screws — alt. name for ISO 10642 countersunk.
- Flange Button Head Socket — ISO 7380-2 (button with collar/flange).
- Low Head Socket Cap — DIN 7984: reduced head height for tight clearances.
- Socket Head Shoulder Screws — ISO 7379: precision shoulder for sliding/rotating joints.
Practical Size Charts (Metric)
Hex key sizes and ranges are typical; always confirm with the product drawing on the PDP.
Socket Head Cap Screws — ISO 4762 / DIN 912
| Thread (M) | Hex Key | Common Length Range |
|---|---|---|
| M3 | 2.5 mm | 6–40 mm |
| M4 | 3 mm | 8–60 mm |
| M5 | 4 mm | 10–80 mm |
| M6 | 5 mm | 10–100 mm |
| M8 | 6 mm | 16–120 mm |
| M10 | 8 mm | 20–150 mm |
| M12 | 10 mm | 25–160 mm |
| M16 | 14 mm | 30–200+ mm |
| M20 | 17 mm | 40–200+ mm |
| M24 | 19 mm | 50–200+ mm |
Flat Head Socket (Countersunk) — ISO 10642 / DIN 7991
| Thread (M) | Hex Key | CSK Angle | Common Length Range |
|---|---|---|---|
| M3 | 2 mm | 90° | 6–25 mm |
| M4 | 2.5 mm | 90° | 8–40 mm |
| M5 | 3 mm | 90° | 10–50 mm |
| M6 | 4 mm | 90° | 12–60 mm |
| M8 | 5 mm | 90° | 16–80 mm |
| M10 | 6 mm | 90° | 20–100 mm |
| M12 | 8 mm | 90° | 25–120 mm |
Socket Button Head — ISO 7380-1
| Thread (M) | Hex Key | Head Profile | Common Length Range |
|---|---|---|---|
| M3 | 2 mm | Low, domed | 6–25 mm |
| M4 | 2.5 mm | Low, domed | 8–30 mm |
| M5 | 3 mm | Low, domed | 10–40 mm |
| M6 | 4 mm | Low, domed | 12–60 mm |
| M8 | 5 mm | Low, domed | 16–60 mm |
| M10 | 6 mm | Low, domed | 20–60 mm |
Button Head with Collar/Flange — ISO 7380-2
| Thread (M) | Hex Key | Note |
|---|---|---|
| M4 | 2.5 mm | Small collar for extra bearing |
| M5 | 3 mm | — |
| M6 | 4 mm | — |
| M8 | 5 mm | — |
| M10 | 6 mm | — |
Low Head Socket Cap — DIN 7984
| Thread (M) | Hex Key | Head Height | Common Length Range |
|---|---|---|---|
| M4 | 3 mm | Reduced vs DIN 912 | 8–30 mm |
| M5 | 4 mm | Reduced | 10–40 mm |
| M6 | 5 mm | Reduced | 12–50 mm |
| M8 | 6 mm | Reduced | 16–60 mm |
| M10 | 8 mm | Reduced | 20–60 mm |
| M12 | 10 mm | Reduced | 25–80 mm |
Socket Grub / Set Screws — ISO 4026/4027/4028/4029
| Thread (M) | Hex Key | Point Style | Typical Lengths |
|---|---|---|---|
| M4 | 2 mm | Flat / Cone / Dog / Cup | 4–16 mm |
| M5 | 2.5 mm | Flat / Cone / Dog / Cup | 5–20 mm |
| M6 | 3 mm | Flat / Cone / Dog / Cup | 6–24 mm |
| M8 | 4 mm | Flat / Cone / Dog / Cup | 8–32 mm |
| M10 | 5 mm | Flat / Cone / Dog / Cup | 10–40 mm |
| M12 | 6 mm | Flat / Cone / Dog / Cup | 12–48 mm |
Socket Head Shoulder Screws — ISO 7379
| Shoulder Ø (mm) | Typical Thread | Hex Key | Shoulder Lengths |
|---|---|---|---|
| 5–6 | M4–M5 | 3 mm | 6–20 mm |
| 8–10 | M6–M8 | 5 mm | 8–40 mm |
| 12–16 | M8–M10 | 6–8 mm | 10–60 mm |
| 20–25 | M12–M16 | 10–14 mm | 12–80 mm |
Materials Used for Socket Screws
- Alloy Steel (quenched & tempered) — highest strength; typically black oxide/oiled.
- Stainless Steel — A2 (304) for general corrosion; A4 (316) for marine/chemical.
- Carbon Steel — 8.8/10.9, often zinc plated for general duty.
- Brass — electrical, non-sparking, decorative.
- Engineering Plastics — specialty, non-conductive, light duty.
Common finishes: black oxide, zinc, zinc-nickel, phosphate, Geomet/Dacromet, passivated stainless. HDG is uncommon for socket styles due to thread/socket fit.
Property Classes / Grades (Metric)
- Alloy Steel Socket Caps: 12.9 (most common), 10.9 where specified.
- General Steel: 8.8, 10.9 (button/csk/low-head often 8.8/10.9).
- Stainless: A2-70, A4-70, A4-80 (higher strength).
- Set/Grub Screws: typically high hardness (≈ 12.9 class) — check spec.
Standards Summary
- ISO 4762 (DIN 912): Socket Head Cap Screws
- ISO 10642 (DIN 7991): Flat Head / Countersunk Socket
- ISO 7380-1/-2: Button Head (plain / with collar)
- DIN 7984: Low Head Socket Cap
- ISO 4026 / 4027 / 4028 / 4029 (DIN 913 / 914 / 915 / 916): Set/Grub Screws (flat / cone / dog / cup)
- ISO 7379: Socket Head Shoulder Screws
FAQs
Are ISO and DIN socket screws interchangeable?
Often yes—ISO is the modern equivalent with minor dimensional/tolerance updates. Always verify with the drawing.
What hex key size should I use?
Refer to the charts above. Sizes can vary slightly by manufacturer; check the PDP drawing.
Can I use hot-dip galvanised socket screws?
Generally no—coating thickness affects socket and threads. Prefer zinc, zinc-nickel, or stainless for corrosion resistance.
