Bolt grades are two numbers. For grade 8.8, the first 8 means a tensile strength of about 800 N/mm², and the second 8 means yield is 80 percent of that.
Common choices
- Grade 8.8: the standard bolt for most structural connections.
- Grade 10.9: higher strength, often used where bolts are preloaded.
Preloaded bolts
Some connections need bolts tightened to a set preload so friction carries the load. These are specified by the engineer and tightened to a controlled method.
Bolts for galvanised steel should be galvanised too. Our bolt quantities tool helps count sets.
