Know what to ask for: the 5 key fastener descriptions
Ordering fasteners can be confusing without the right terminology. Whether you’re speaking with a supplier or placing an order online, these five essential specs will help ensure you get the exact fastener you need.
1. Size (diameter x length)
The most basic but critical descriptor. It includes:
- Diameter (e.g. M10, meaning 10mm)
- Length (e.g. 50mm, total length of the bolt from underneath the head)
Example: M10 x 50 = 10mm wide and 50mm long
Tip: Always measure from under the head unless you're using countersunk screws.
2. Thread type and pitch
Fasteners come in various thread types:
- Metric (e.g. M6, M8)
- UNC/UNF (imperial coarse/fine)
- Self-tapping or self-drilling for sheet metal or timber
Pitch refers to the distance between threads. Fine threads offer more grip in thin materials.
>> Download our head styles and drive types PDF
3. Material
Choose based on strength, durability, and environmental exposure.
- Carbon steel: General purpose, strong
- Stainless steel: Corrosion resistant, ideal outdoors
- Brass, nylon, or alloy: For specialised needs
4. Finish or coating
Fasteners may be coated for corrosion protection or appearance.
- Zinc-plated: Basic corrosion resistance
- Hot-dip galvanised: For harsh environments
- Black oxide or chrome: Aesthetic or anti-seize properties
>> Download our materials and finishes PDF
5. Strength grade
Grades indicate tensile strength. Common standards include:
- Metric bolts: Property Class 4.6, 8.8, 10.9, 12.9
- Imperial bolts: Grade 5, 8
- Stainless: A2-70, A4-80 (based on ISO)
Always check project specs or engineering requirements before choosing.
>> Download our tensile strengths PDF
Need help specifying your fasteners?
United Fasteners’ expert team is here to support tradespeople, builders and engineers with technical advice and fast turnaround.
Get the right fastener, first time. Talk to our technical team 1300 580 954 or see our technical fastener guides today.