Fastening Know-How
Types of Screws: Head, Drive, Thread and Application Chart
Screws are sorted four ways: by the job they do, by thread, by head shape and by drive. Choose the job first, then the thread that suits the material, then the head and drive that suit assembly and access.
How Screw Types Are Classified
A screw differs from a bolt mainly in how it is used: a screw is turned into a tapped or formed thread in the part itself, while a bolt passes through and is held by a nut. In practice the terms overlap, and a hex cap screw and a hex bolt can look almost the same.
The tables below cover the families most OEM buyers meet. For head shapes in more depth see screw head types, and for hex cap screw sizes see the bolt size chart.
Types of Screws by Application
Start here: the job decides most of the rest.
| Screw type | How it holds | Goes into | Read more |
|---|---|---|---|
| Machine screw | Uniform machine thread into a tapped hole or a nut | Metal parts, tapped holes, nuts | Machine screws vs other fasteners |
| Cap screw (hex or socket head) | Machine thread, tightened by the head to clamp a joint | Tapped holes and through holes with nuts | Hex cap screw sizes |
| Sheet metal screw | Sharp, widely spaced thread that forms its own path in a pilot hole | Thin sheet metal, some plastics | Self-tapping screws |
| Self-tapping screw | Cuts or forms its own mating thread in a pilot hole | Metal and plastic | Self-tapping screws |
| Self-drilling screw (Tek) | Drill-bit point makes the hole and the thread in one step | Sheet steel and light framing | Tek screws |
| Thread-forming screw | Displaces material instead of cutting it, so no chips | Ductile metals and plastics | Ask our team |
| Set screw (grub screw) | Point bears on a shaft to stop movement | Collars, pulleys, gears | Set screws and grub screws |
| Shoulder screw | Precision unthreaded shoulder acts as a pivot or guide | Pivots, linkages, slides | Shoulder screws |
| Wood screw | Coarse, tapered thread that grips wood fibre | Timber and board | Ask our team |
| Structural screw | Large-diameter screw for structural timber connections | Timber framing | Structural screws |
Types of Screws by Head
The head sets how the screw sits on the surface and how much bearing area it gives. Full guide: screw head types.
| Head | Profile | Typical use |
|---|---|---|
| Pan | Low, slightly domed with flat bearing face | General assembly, electronics, sheet metal |
| Flat (countersunk) | Sits flush in a countersunk hole | Flush surfaces, hinges, panels |
| Oval | Countersunk with a domed top | Flush fit with a finished look |
| Button | Low, rounded socket head | Low-profile fixing where a cap head is too tall |
| Truss | Wide, low dome with a large bearing face | Thin sheet and oversized holes |
| Hex and hex washer | Wrench-driven hex, sometimes with an integral washer | High torque, sheet metal and machinery |
| Socket head cap | Tall cylindrical head with a hex socket | Machinery and tight spaces needing high clamp load |
| Fillister | Tall, rounded cylindrical head | Counterbored holes |
Types of Screws by Drive
The drive decides how much torque can be applied before the tool slips. Compare the two most common in Torx vs Phillips.
| Drive | Torque transfer | Notes |
|---|---|---|
| Slotted | Low; slips easily | Simple, still used for adjustment screws |
| Phillips | Moderate; tends to cam out under high torque | Very common on assembly lines |
| Pozidriv | Better than Phillips | Looks similar; use the matching bit |
| Square (Robertson) | Good; holds the screw on the bit | Common in woodworking and panels |
| Hex socket | High, compact | Cap, set and button head screws |
| Hexalobular (Torx) | High, low cam-out | Automotive and electronics assembly |
| External hex | High, wrench or socket | Hex and hex washer heads |
| Security drives | Needs a special bit | Tamper-resistant enclosures and public equipment |
Types of Screws by Thread
Thread type follows the material the screw goes into. To read thread size and pitch, see how screws are measured.
| Thread | Description | Used for |
|---|---|---|
| Unified coarse (UNC) | Standard inch machine thread with fewer threads per inch | General assembly; faster to install, tolerant of damage |
| Unified fine (UNF) | More threads per inch than UNC | Thin walls, fine adjustment, vibration-prone joints |
| Metric coarse and fine | ISO metric threads, size and pitch in millimetres | Metric designs worldwide |
| Thread-cutting | Flutes cut a mating thread and remove chips | Harder metals and brittle plastics |
| Thread-forming | Rolls a mating thread without chips | Ductile metals and many plastics |
| Spaced or high-low | Deep, widely spaced thread for soft material | Plastics, wood and sheet metal |
How to Choose the Right Screw
Work through four questions in order. What is the screw going into, and is there a tapped thread or nut? Does the joint need clamp load, a pivot, or just a light hold? How will it be assembled: by hand, by a power driver on a line, or by a robot? Does the environment call for stainless steel or a coating?
If a part also needs a strength grade, check the bolt grade chart. For supply of standard and made-to-print screws, see bolts and screws.
Types of Screws FAQ
What are the main types of screws?
By job, the common families are machine screws, cap screws, sheet metal screws, self-tapping and self-drilling screws, thread-forming screws, set screws, shoulder screws and wood screws.
What is the difference between a screw and a bolt?
A screw usually threads into the part or forms its own thread, while a bolt passes through the parts and is tightened with a nut. Many fasteners, such as hex cap screws, can be used either way.
What is the difference between self-tapping and self-drilling screws?
A self-tapping screw needs a pilot hole and then cuts or forms its thread. A self-drilling screw has a drill point that makes the hole itself.
Which screw drive is strongest?
Hex socket, hexalobular (Torx) and external hex drives transfer the most torque with the least slipping. Slotted and Phillips drives slip more easily.
Which screws should I use in plastic?
Thread-forming or spaced, high-low thread screws designed for plastic, sized to the boss so the plastic does not crack.
Need Screws Supplied at Volume?
Send us part numbers or a drawing. We supply standard and made-to-print screws, and can run them on a managed replenishment programme.