Types of Screws and Bolts: Heads, Drives and Threads
Updated: 2026-10-28
Screws and bolts are classified by what they fasten, their head style, their drive and their thread. When no standard combination fits, those elements are combined into a custom fastener.
Main fastener types
Type
Description
Typical uses
Machine screws
Small diameter, driven with a screwdriver into tapped holes or nuts
Electronics, appliances, instruments
Hex bolts
Hex head tightened with a wrench, often with a nut
Machinery, structures
Socket head cap screws
Hex socket head for high torque with an Allen key
Machinery, tooling, equipment
Thread-forming / self-tapping screws
Form their own thread in a pilot hole
Sheet metal, plastics
Set screws
Headless; hold a part with the point
Collars and pulleys on shafts
Shoulder screws
Precision unthreaded shoulder
Pivots, locating
Threaded rod and studs
Thread along the full length or both ends
Flanges, machine mounting
Head styles
Head
Notes
Pan
The most common rounded head
Flat (countersunk)
Conical head that sits flush in a countersink
Oval
Countersunk head with a domed top
Truss
Large, low head for thin sheet
Hex and hex flange
Wrench-driven; flange spreads the load
Low head
For tight clearances
Drive types
Drive
Notes
Phillips (cross)
Most common screwdriver drive
Slotted
Traditional; tools slip easily
Hex socket
High torque with hex keys
Hexalobular (6-lobe)
Resists cam-out, good torque transfer (ISO 10664)
Tamper-resistant
Requires special tools
Thread types
Thread
Notes
Metric coarse
The default metric thread (e.g. M6×1)
Metric fine
Finer pitch for thin walls and vibration (e.g. M6×0.75)
Unified (UNC / UNF)
Inch threads used in North America and aerospace
Pipe threads
Parallel (G / NPS) and tapered (R, NPT) threads for piping
FAQ
What is the difference between a screw and a bolt?
Usage varies, but screws are usually driven into a tapped hole or form their own thread, while bolts are typically used with a nut and tightened with a wrench.
What if no standard screw fits my design?
Head, drive, thread and material can be combined into a custom fastener. Send the drawing and we will suggest the process.