Machine Screw
Screws · machine bolt · stove bolt
Definition: A machine screw is a small, fully threaded fastener with a uniform diameter, driven into a pre-tapped hole or used with a nut. Sizes run under 1/4 in. (or M6).
Anatomy
■ Head■ Shank■ Threads■ Point
Governing standards: ASME B18.6.3 · ANSI B1.1
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| #4-40 | M2.5 x 0.45 | 7/32 | 3/32 |
| #6-32 | M3.5 x 0.6 | 9/32 | 7/64 |
| #10-32 | M5 x 0.8 | 3/8 | 1/8 |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Steel | low carbon steel | 60,000 | None |
| Stainless 18-8 | 304 stainless | 70,000 | None |
Materials
- Steel (zinc)
- Stainless steel 18-8 / 316
- Brass
- Nylon
- Aluminum
Pros & Cons
Pros
- Fine sizes for precise, compact assemblies
- Wide range of head styles and drives
- Cheap and standardized
Cons
- Not for structural loads
- Small sizes strip easily
- Needs a tapped hole or nut
Typical Uses
- Electronics and appliances
- Small mechanisms and hinges
- Instrument panels
- Any small tapped-hole assembly
Alternatives & Related
- Socket Head Cap Screw — Higher strength in a similar size range
- Self-Tapping Screw — Forms its own thread in sheet metal, no tap needed
Where to Buy
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FAQ
What is a machine screw used for?
Fastening small parts into tapped holes or with nuts — electronics, appliances, hinges, and precision mechanisms.
Machine screw vs bolt?
By convention, machine screws are under 1/4 in. (M6) and fully threaded; bolts are larger and often partially threaded. Functionally they overlap.