Machine Screws

Screw Size (Diameter & Thread)

Typical Tap Drill Size

Key Characteristics & Common Applications

M2

1.6 mm

Very small, for precision electronics, small PCB mounts, and delicate instruments.

M3

2.5 mm

A common size for small assemblies, 3D printer parts, light-duty brackets, and consumer electronics.

#6-32

#36 (≈3.6 mm)

A standard U.S. size, famously used for computer case panels and also common in electrical outlets, switch plates, and general light hardware.

3/16"

#23 (≈8.5 mm)

Less common than metric or UNC sizes, but used in some older equipment, machinery, and specific automotive applications.

M4

3.3 mm

A versatile size for general-purpose fabrication, automotive components, machinery guards, and medium-duty assemblies.

1/4"-20

#7 (≈4.0 mm)

The most common 1/4" size. A workhorse for industrial machinery, woodworking jigs, bench vises, and heavy-duty consumer products.

M6

5.0 mm

A strong, standard size for structural framing, furniture assembly (e.g., table legs), automotive brackets, and outdoor equipment.

#8-32

#29 (≈3.4 mm)

Slightly larger and stronger than a #6-32 screw, often used as a general-purpose screw in HVAC, electronics chassis, and machinery.

5/16"-18

'F' (≈6.9 mm)

Provides high strength for demanding applications like engine components, trailer hitches, and structural steel connections.

M8

6.8 mm

A heavy-duty metric size, suitable for automotive suspension parts, large machinery, and structural supports in metal framing.

M10

8.5 mm

Used for high-stress applications, such as securing large bearings, heavy machinery frames, and structural steelwork.