IS 1364 Part 1 : 2017Hexagon Head Bolts, Screws and Nuts of Product Grade A and B - Part 1: Hexagon Head Bolts (Size Range 1.6 mm to 64 mm)

IS 1364 (Part 1) is the specification for hexagon head bolts, screws and nuts of product grade A and B — the headline specification for hex bolts and nuts used in structural connections, mechanical assemblies, and general engineering. The code aligns with international ISO 4014 / 4017 / 4032 standards.

Use IS 1364 hex bolts when designing or specifying: - Structural steel connections (IS 800:2007) — bolted joints in beams, columns, gussets, base plates - Bridge connections (IRC:24:2010, IRC:22:2008) - Crane / equipment foundations — anchor bolts (often M20 to M64) - Pre-engineered building (PEB) assembly - Steel rolling-stock connections (railways) - Storage rack assembly - Heavy machinery installation (motor / pump / compressor mounting) - Concrete-to-steel anchoring (with chemical / mechanical anchor base)

IS 1364 has multiple Parts: - Part 1: Hex head bolts (full-shank with hex head — this code) - Part 2: Hex head screws (full-thread with hex head) - Part 3: Hex nuts (style 1 and 2) - Part 4: Hex thin nuts - Part 5: Slotted nuts + castle nuts

'Product grade A' = tighter tolerance (precision); 'product grade B' = looser tolerance (general use). Most structural / construction applications use Product Grade B; precision machinery uses Grade A.

Property classes (per IS 1367 Part 3 / ISO 898-1):

| Property class | Tensile strength (MPa) | Yield strength (MPa) | Use | |---|---|---|---| | 4.6 | 400 | 240 | General mild steel — non-structural | | 5.6 | 500 | 300 | General use — light structural | | 8.8 | 800 | 640 | Standard structural — most common | | 10.9 | 1040 | 940 | High-strength structural; pre-loaded connections | | 12.9 | 1220 | 1100 | Very high-strength; critical applications |

First digit × 100 = nominal tensile strength (MPa). Second digit / 10 × first digit = nominal yield (e.g., 8.8 → 0.8 × 800 = 640 MPa).

Bolt + nut compatibility: - 8.8 bolt with 8 / 10 / 12 nut - 10.9 bolt with 10 / 12 nut - Nut yield < bolt yield (so nut deforms first under over-load — preferred failure mode)

Standard bolt sizes (IS 1364 Part 1): - M3, M4, M5, M6, M8, M10, M12, M16, M20, M24, M30, M36, M42, M48, M56, M64 - M16 + M20: most common in structural steel construction - M24 + M30: heavy structural / bridge - M36 + above: anchor bolts, mega-equipment

Bolt length: - Per design (grip length + nut + thread engagement) - Standard increments: 5 mm increments to 50 mm length; 10 mm to 100; 25 mm beyond - Long bolts (> 200 mm) often custom

Surface treatment: - Zinc-plated (electroplated): light corrosion protection; for indoor / dry use - Hot-dip galvanised (HDG): heavy zinc coating; for outdoor / marine - Phosphated + oiled: short-term corrosion protection - Stainless steel (per IS 6603): for severe corrosion / chemical exposure (typically grade A4-70 / A4-80 stainless)

Pre-load + tightening (per IS 800:2007):

| Bolt size + grade | Specified pre-load (kN) | |---|---| | M16 grade 8.8 | 99 | | M20 grade 8.8 | 154 | | M24 grade 8.8 | 221 | | M30 grade 8.8 | 351 | | M36 grade 8.8 | 511 |

(For pre-loaded connections per IS 800:2007; applied by torque wrench or turn-of-the-nut method.)

Hex head dimensions (IS 1364 Part 1, simplified):

| Bolt size (mm) | Hex across flats (mm) | Head height (mm) | |---|---|---| | M6 | 10 | 4 | | M8 | 13 | 5.3 | | M10 | 17 | 6.4 | | M12 | 19 | 7.5 | | M16 | 24 | 10 | | M20 | 30 | 12.5 | | M24 | 36 | 15 | | M30 | 46 | 18.7 | | M36 | 55 | 22.5 |

Bolt hole size: - Standard hole = bolt diameter + 2 mm clearance (e.g., M20 bolt → 22 mm hole) - Slotted hole (for variable assembly): bolt diameter + 8 mm long - Per IS 800:2007 hole class

Bolt connection types: - Bearing connection: bolt transfers load by bearing on hole walls; relies on bolt shear capacity - Friction-grip (high-strength friction grip — HSFG) connection: pre-loaded bolt clamps plates; load transferred by friction at faying surface; no bolt shear - Higher capacity per bolt - Used for fatigue-loaded connections (cyclic loads) - Requires controlled tightening - Surface preparation critical (sandblast, grit-blast for HSFG)

Fatigue performance: - Bearing connection: poor fatigue (stress concentration at hole) - HSFG connection: excellent fatigue (clamping prevents stress concentration) - For dynamic loads (cranes, bridges, machine bases): HSFG mandatory

Thread engagement: - Minimum 1 × bolt diameter for full strength - Standard: 1.5 × diameter for safety margin - Additional washer / plate for soft material connections

Anchor bolts (concrete to steel): - L-bolt, J-bolt, or headed stud cast in concrete - Hex nut + plate washer at the steel base - Anchor design per ACI 318 Annex D OR IS 1893 / IS 13920 for seismic

• IS 1364 Part 2-5 — hex screws, nuts, thin nuts, slotted nuts.
• IS 800:2007 — code of practice for general construction in steel (bolt design).
• IS 4923:1997 — hollow steel sections.
• IS 808:1989 — dimensions for rolled steel sections.
• IS 1367 (Parts 1-15) — technical supply conditions for fasteners (mechanical properties, tolerances).
• IS 6760 — slotted countersunk head wood screws.
• IS 6603 — stainless steel bolts, screws, nuts (for corrosion-resistant applications).
• IS 6649 — washers for high-strength friction-grip bolts.
• IS 5369 — plain washers.
• IS 1370 — coupling nuts.
• IS 1366 — slotted countersunk head screws.
• IS 1369 — wedge-shaped washers.
• IS 4759 — hot-dip galvanising of iron and steel.
• IS 9595 — recommendations for metal arc welding (alternative to bolting).
• IS 1893 Part 1:2016 — earthquake design (seismic load on connections).
• IS 13920:2016 — ductile detailing.
• IRC:24:2010 — steel road bridges.
• IRC:22:2008 — composite construction.
• ASTM A325 / A490 — international counterparts for high-strength bolts.
• ISO 4014 / 4017 / 4032 — international counterparts for hex bolts / screws / nuts.

1. Wrong property class for application. Grade 4.6 bolt in critical structural connection = under-strength; grade 12.9 in routine connection = over-design. Match grade to design; usually 8.8 for structural. 2. No bolt + nut grade match. Nut grade < bolt grade preferred (so nut deforms first); reverse causes thread strip + sudden bolt failure. 3. No surface treatment for outdoor application. Bolt rusts, fastener loosens, joint fails. HDG for outdoor; stainless for marine. 4. Insufficient thread engagement. < 1 × bolt diameter; bolt strips thread before reaching design load. Maintain 1-1.5 × diameter engagement. 5. Pre-load not applied (HSFG connection treated as bearing). Friction not engaged; connection capacity halved or worse. Specify and apply pre-load per IS 800:2007. 6. Surface preparation skipped for HSFG. Painted / rusted surfaces have low friction; no clamping. Sandblast or grit-blast for HSFG faying surfaces. 7. Wrong bolt hole size. Hole too tight = no insertion; hole too large = excessive movement. Standard hole = bolt + 2 mm; verify. 8. Inadequate tightening verification. Torque wrench accuracy ±10 %; turn-of-the-nut method more accurate. Random spot-check on critical connections. 9. Re-using bolts after disassembly. High-strength bolts (grade 10.9, 12.9) lose pre-load capacity after stretching; do not re-use. 10. No quality test on bolt batch. Counterfeit bolts (low-grade with high-grade markings) common. Spot-test tensile + hardness on critical batches. 11. Anchor bolts cast at wrong depth / position. Embedment too shallow; foundation breakout. Per design; verify position before concrete pour. 12. No corrosion inhibitor in concrete around anchor bolt. Anchor bolt corrodes; loosens. Use corrosion-inhibitor in concrete OR sleeved bolt. 13. Confusing bolt grade with property class. 'Grade 8.8' refers to property class; 'product grade A or B' refers to dimensional tolerance. Both required to specify.

Bolt connection design + assembly cascade:

1. Connection design (IS 800:2007): - Bearing or HSFG / friction-grip - Bolt size + property class - Number of bolts + spacing - Edge distance, pitch, gauge 2. Specification in BOQ: - 'M20 × 60 mm long, hex head bolt + nut + washer per IS 1364 Part 1, property class 8.8, hot-dip galvanised' - Per shop drawing tagged on each connection 3. Procurement — ISI marked bolts from BIS-licensed manufacturer with batch test certificate. 4. Storage — dry, organised by size + grade. 5. Installation: - Bolts inserted; washer under nut - Hand-tight initial assembly - Final torque OR turn-of-the-nut method (for pre-loaded HSFG) - Periodic spot-check by quality engineer 6. Quality acceptance: - Visual: bolt + nut + washer in place; protrusion correct (≥ 2 thread above nut) - Torque verification on random sample - For HSFG: friction grip verified per IS 800:2007 7. Maintenance: - Periodic inspection for loosening, corrosion - Re-tightening if needed (typically not for HSFG; bearing connections may loosen) - Replacement of corroded / damaged bolts

Field error rates: - Wrong size bolt at site: ~5 % typical (minor; correctable) - Wrong grade bolt: ~1 % (serious; structural risk) - Inadequate torque: ~10-20 % (HSFG connections vulnerable to friction loss) - Random testing + supervisor check critical for ensuring quality

IS 1364 Part 1 is one of the most-used fastener codes in Indian construction. The bolt is small but the connection is everything — design rigor + quality procurement + careful installation + periodic inspection together make safe steel structures.