What is a Hex Cap Screw? What is a Hex Bolt?
In the industrial fastener field, Hex Cap Screws and Hex Bolts are two common but often confused fasteners. Both have hexagonal heads and are tightened using wrenches or sockets. To accurately distinguish them, you first need to understand their basic structure and methods of use.
Is the Tail End of a Hex Cap Screw Pointed?
The tail end of a hex cap screw is usually not pointed, but rather flat or slightly chamfered with a rounded end.
Industrial hex cap screws—especially those meeting standards like ASME B18.2.1 or ISO 4014/4017—typically have a:
- Flat end or
- Chamfered rounded end
This tail design helps:
- Align the screw easily with the tapped hole
- Improve assembly accuracy
- Prevent damage to the threads or workpieces
Difference from Pointed-End Screws
If the tail is pointed, it is likely a:
- Self-tapping screw
- Wood screw
- Drywall screw
These are designed to cut or form their own threads and penetrate materials without pre-drilled holes, and are not standard industrial hex cap screws.
Can You Distinguish Hex Cap Screws and Hex Nuts by Naked Eye?
It is difficult to distinguish hex bolts and hex cap screws by naked eye because they look very similar—both have hex heads and threaded shafts.
However, some subtle points can help differentiate them:
- Tail shape:
- Hex cap screws usually have a smooth, chamfered tail for easy screwing into tapped holes.
- Hex bolts may have a flat or cut tail that looks a bit rougher.
- Thread tolerance and length:
- Hex cap screws have finer thread tolerance and are often partially threaded.
- Hex bolts may have coarser threads and can be fully or partially threaded.
- Standard markings:
- Sometimes, hex cap screws have manufacturer or grade markings on the head, but this is not always the case.
Hex Cap Screw vs Hex Bolt: Main Differences
| Feature | Hex Cap Screw | Hex Bolt |
| Underside of head | Usually with washer face and chamfer for more even load distribution | Mostly no washer face |
| Thread tolerance | Higher manufacturing precision, suitable for precision assemblies | Coarser threads, lower precision |
| Thread length | Mostly partially threaded | Can be partially or fully threaded |
| Typical usage | Can be directly screwed into tapped holes | Usually pass through structures and used with nuts |
| Applicable standards | ASME B18.2.1 / B18.3 | ASME B18.2.1 |
Application Areas
- Hex Cap Screws:
- Precision equipment
- Internal thread assemblies
- Instruments and machinery
- Hex Bolts:
- Steel structure connections
- Heavy equipment installation
- Construction, bridges, shipbuilding, etc.
Common Materials
- Carbon steel: ASTM A307, A325 (suitable for construction structures)
- Stainless steel: 304, 316 (for corrosion-resistant environments)
- Alloy steel: Grade 10.9, 12.9 (high strength connections)
- Nickel alloys: Monel, Inconel (used in high temperature or corrosive environments)
Contact MT.BOLTS
MT.BOLTS offers a wide range of industrial fasteners, including hex cap screws and hex bolts. Our products strictly comply with international standards, covering various materials and specifications, widely used in petrochemical, power generation, equipment manufacturing, marine engineering, and many other industries.
Feel free to contact us to learn more about fasteners and purchase quality products. Our professional team provides full technical support and selection advice.
