Bolts vs screws — the real difference
The common rule of thumb: a bolt is designed to pair with a nut and is tightened by turning the nut, while a screw cuts its own thread into the material it’s driven into and is tightened by turning the screw head itself. In practice the terms get used loosely, but that distinction is the useful one when you’re specifying parts.
The common types you’ll run into
- Hex bolts — the standard six-sided head, used with a nut for general structural and machine assembly
- Machine screws — smaller, threaded fully or partially, used with a tapped hole or nut for precision assembly
- Self-tapping screws — cut their own thread, common in sheet metal and plastic
- Nuts — hex, lock, and wing nuts each trade off strength, vibration resistance and ease of hand-tightening differently
- Washers — flat washers spread load, lock washers resist loosening under vibration
Material matters as much as shape
Stainless steel resists corrosion but costs more; mild steel with a plating is cheaper but needs the right coating for the environment; brass is common where electrical conductivity or a non-sparking property matters. The right material depends on the environment the fastener will actually sit in, not just the load it carries.
Our take
We stock exactly this range — bolts, screws, nuts, washers, down to micro sizes — at 3fparts.com, with no minimum order quantity.