# The Engineer's Guide to International Fastener Standards
In global engineering, consistency is everything. Fasteners are governed by several international standards organizations to ensure that a bolt manufactured in India fits a nut manufactured in Germany.
1. ASTM International (USA)
ASTM standards are widely used in the Americas and the oil and gas industry. Common specifications include **ASTM A193** (Alloy steel for high temperature) and **ASTM A325** (structural bolts).2. ISO (International Organization for Standardization)
ISO is the global benchmark for metric fasteners. **ISO 4014** (Hex head bolts) and **ISO 4017** (Hex head screws) are the most common metric specifications used worldwide.3. DIN (Deutsches Institut für Normung - Germany)
While many DIN standards are being replaced by ISO, many are still used in heavy machinery and automotive sectors. **DIN 931** and **DIN 933** remain industry staples.4. ASME (American Society of Mechanical Engineers)
ASME focuses on the dimensional standards and pressure vessel codes. **ASME B18.2.1** covers square and hex bolts and screws in imperial units.Cross-Reference: Global Hex Head Bolt Standards
| Fastener Type | ISO Standard | DIN Standard | ASME Standard |
|---|---|---|---|
| Hex Head Bolt (Partial Thread) | ISO 4014 | DIN 931 | ASME B18.2.1 |
| Hex Head Screw (Full Thread) | ISO 4017 | DIN 933 | ASME B18.2.1 |
| Hex Nut | ISO 4032 | DIN 934 | ASME B18.2.2 |
| Plain Washer | ISO 7089 | DIN 125 | ASME B18.22.1 |
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