Hex Nuts Guide: Metric Sizes, Threads & Stainless Steel Options
Hex nuts provide one of the simplest reusable ways to clamp parts with a bolt or threaded stud. The six flats are easy to grip with a spanner or socket, and the geometry is.
Hex nuts provide one of the simplest reusable ways to clamp parts with a bolt or threaded stud. The six flats are easy to grip with a spanner or socket, and the geometry is standardised across common metric sizes. The key purchasing details are thread diameter, pitch, material, style and the mechanical property required by the joint.
A nut that screws on by hand is not automatically the correct nut. The pitch, thread tolerance and strength compatibility all matter. In corrosion-sensitive assemblies, matching the nut material to the bolt and the environment can also reduce maintenance problems.
Quick answer: Hex nuts provide one of the simplest reusable ways to clamp parts with a bolt or threaded stud.
What to know about hex nuts guide
Metric thread compatibility
The nut must match both nominal diameter and pitch. M6×1.0 and M6×0.75 are different threads even though they share the M6 diameter designation.
Nut style
Regular hex nuts are general-purpose components. Thin nuts, high nuts, Nyloc nuts and dome nuts change height or add a specific function.
Material choice
SS304 hex nuts are common in corrosion-resistant general assemblies. Carbon and alloy steel nuts are selected by property class and coating where higher strength or lower cost is needed.
Thread engagement
Adequate engagement is necessary for the joint to develop the intended capacity. Very short engagement can strip threads before the bolt reaches the expected load.
How to choose the right fastener
- Start with bolt thread: Match diameter and pitch exactly.
- Check nut style and height: Space constraints and required thread-stripping resistance influence style.
- Match strength levels: Use a nut suitable for the bolt's mechanical property requirements.
- Assess corrosion: Match or intentionally pair materials based on the environment.
- Plan locking separately: A regular hex nut is not automatically a vibration-locking nut; use a suitable locking strategy where required.
Quick comparison
| Nut type | Main function | Typical use |
|---|---|---|
| Regular hex nut | General clamping | Bolts and studs |
| Nyloc nut | Prevailing torque | Vibration-resistant joints |
| Dome nut | Covered thread end | Appearance and edge protection |
| Thin nut | Reduced height | Space-constrained or locking arrangements |
A practical ordering workflow
Before placing an order for hex nuts guide, turn the application into a short specification. Start with the mating thread and physical envelope, then confirm the head or drive, material and finish. If the fastener is part of a loaded, vibrating, outdoor or frequently serviced joint, add the relevant mechanical, corrosion and maintenance requirements before choosing a SKU.
For repeat purchases, record the exact approved description in your bill of materials or purchasing system instead of relying on a photograph or an old sample. That record should include the dimensions that control fit, the material or property class, the finish, and any standard or certificate requirement. This makes replacement orders easier to compare and helps prevent accidental substitutions.
When a dimension, torque value, strength requirement or corrosion condition is safety-critical, use the applicable engineering drawing, current standard and manufacturer documentation as the final authority. Catalogue guidance is useful for narrowing choices, but it should not override the requirements of the actual joint.
How to verify the specification before ordering
Make the first verification on the actual assembly or approved drawing. For start with bolt thread, match diameter and pitch exactly. For check nut style and height, space constraints and required thread-stripping resistance influence style. Do not assume that an older fastener removed from the machine is still the approved specification; previous repairs may have introduced substitutions.
If the part is being introduced into production, buy a small validation quantity before committing to a large lot. Check thread engagement by hand, seating of the head or nut, tool clearance, surface marking, interference with nearby parts and the condition of the mating thread after assembly. Where traceability or mechanical properties matter, compare received markings and documents with the purchase specification. This small verification step is especially useful when changing suppliers, materials, finishes or dimensional standards.
Common mistakes to avoid
- Ordering by spanner size instead of thread size.
- Mixing coarse- and fine-pitch nuts.
- Using a regular nut where the design requires prevailing torque.
- Selecting a nut that is mechanically weaker than the joint requires.
- Assuming all stainless nuts have identical performance.
Recommended products and categories
You can continue from this guide by viewing shop hex nuts, M6 SS304 hex nut and Nyloc locking nuts.
Technical references
The following independent technical references are useful for checking terminology, standards and engineering background. They are provided for reference and do not imply endorsement of any product sold on this site.
Frequently asked questions
What is the standard coarse pitch for M6?
M6 commonly uses 1.0 mm coarse pitch.
Can I use an M6 nut on any M6 bolt?
Only if the pitch and thread form match.
What is the difference between a hex nut and Nyloc nut?
A Nyloc nut includes a non-metallic insert that creates prevailing resistance to rotation; a regular hex nut does not.
Why use a dome nut instead of a regular hex nut?
Dome nuts cover the exposed thread end and can improve appearance and reduce contact with a sharp protruding thread.
Related reading
Final buying checklist
- Confirm the nominal thread diameter and thread pitch.
- Confirm the required length and the correct head-to-tip measuring method.
- Check head style, drive style and installation-tool access.
- Match material and finish to the service environment and mating materials.
- Check strength, locking, documentation and application limits where they matter.
Specify a nut by thread, style, material and mechanical requirement. When those four items match the bolt and the service environment, the joint becomes easier to assemble and maintain.
Ready to select a part? Browse our Screws, Nuts & Bolts catalogue and filter by thread size, material, finish, head style and drive type.