Bolts

A bolt is typically used with a nut to fasten two or more unthreaded components together, providing a strong, secure joint, while a screw is designed to be threaded directly into a material, often creating its own internal thread. Bolts usually require pre drilled holes and rely on tension to hold parts together, whereas screws depend on friction. In short, bolts are for assembling parts with nuts, while screws are for fastening directly into materials.

Bolt grades or property classes define the bolt’s mechanical properties, mainly its tensile and yield strength. For metric bolts, an 8.8 bolt means it has 800 MPa tensile strength and 80% yield strength, while a 10.9 bolt is even stronger. In imperial systems, Grade 5 and Grade 8 bolts serve similar roles, with Grade 8 being higher in strength. These grades ensure the bolt can handle specific loads and stresses safely.

Bolts are made from materials like stainless steel, carbon steel, alloy steel, and high performance alloys such as Inconel, Monel, and Hastelloy. Stainless steel bolts are corrosion resistant and ideal for marine or outdoor use, while alloy steel bolts offer superior strength for industrial or structural applications. The choice of material depends on factors such as environment, temperature, and required load capacity.