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Views: 0 Author: Site Editor Publish Time: 2026-08-29 Origin: Site
Size | Thread pitch (coarse, mm) | Head diameter (pan, mm) | Common lengths (mm) |
|---|---|---|---|
M1.6 | 0.35 | 3.2 | 2–16 |
M2 | 0.4 | 4.0 | 3–20 |
M2.5 | 0.45 | 5.0 | 3–25 |
M3 | 0.5 | 5.6 | 4–30 |
M4 | 0.7 | 7.0 | 5–40 |
M5 | 0.8 | 9.0 | 6–50 |
M6 | 1.0 | 10.5 | 8–60 |
M8 | 1.25 | 14.0 | 10–80 |
M10 | 1.5 | 17.0 | 12–100 |
Head diameters shown are for pan head (ISO 1580). Slotted cheese head (ISO 1207) and countersunk (ISO 2009) have different head dimensions — diameter stays the same.
Screw number | Thread (TPI) | Thread diameter (inch) | Thread diameter (mm) | Common lengths (inch) |
|---|---|---|---|---|
#0 | 80 | 0.060" | 1.5 mm | 1/8–1/2 |
#2 | 56 | 0.086" | 2.2 mm | 1/8–3/4 |
#4 | 40 | 0.112" | 2.8 mm | 1/4–1 |
#6 | 32 | 0.138" | 3.5 mm | 1/4–1.5 |
#8 | 32 | 0.164" | 4.2 mm | 3/8–1.5 |
#10 | 24 | 0.190" | 4.8 mm | 3/8–2 |
#12 | 24 | 0.216" | 5.5 mm | 1/2–2 |
Threads per inch (TPI) shown are the most common (UNC coarse) values. #8-32 means #8 size, 32 threads per inch.
Identify the diameter — machine screws must match the tapped hole. Measure the hole or the mating nut; M4 goes into a 4.0 mm threaded hole, not a 4.0 mm drill hole.
Choose the thread — metric: coarse is the default (M4×0.7); inch: UNC is the default (#8-32). Fine threads (UNF, e.g. #8-36) are used where vibration resistance or finer adjustment matters.
Pick the head style — pan/slotted for general use, countersunk for flush surfaces, socket (hex) for higher torque, Phillips/cross for faster assembly.
Select the material — zinc-plated carbon steel for dry indoor use; stainless steel 304/316 for moisture, outdoor and food environments; brass for decorative or low-corrosion electrical use.
Length — measure from under the head to the tip; add the depth of the tapped hole and the thickness of the part being clamped.
Machine screw | Self-tapping screw | |
|---|---|---|
Threads into | Tapped hole or nut | Material directly (cuts/forms its own thread) |
Needs pre-drilling? | Yes, tapped to size | Pilot hole, no tapping |
Typical uses | Electronics, machinery, appliance assembly | Sheet metal, plastics, wood, drywall |
Hardness | Medium–high | High tip hardness |
A machine screw cannot cut its own thread — forcing one into sheet metal will strip the thread and ruin the part.
Q1: What size is a #8 machine screw? #8 is 0.164" (4.2 mm) thread diameter, most commonly with 32 TPI (#8-32).
Q2: What is the most common machine screw size? M3, M4 and M5 in metric; #6-32 and #8-32 in inch sizes.
Q3: How do I know what size machine screw I need? Measure the thread diameter and pitch of the tapped hole, or match the existing screw with a gauge.
Q4: Can I use a machine screw in wood? No — machine screws need a tapped thread. Use wood screws for wood.
Q5: What's the difference between M4×0.7 and M4×0.5? Thread pitch: M4×0.7 is coarse (0.7 mm per thread), M4×0.5 is fine pitch.
Q6: Are machine screws and self-tapping screws the same? No. Machine screws thread into tapped holes/nuts; self-tapping screws cut their own thread.
Ningbo Weifeng Fastener Co., Ltd. supplies machine screws in metric (M1.6–M10) and inch (#0–#12) sizes, in pan, countersunk, cheese and socket heads, with zinc plating or stainless steel (304/316) — browse our machine screw range or send us your specification for a fast quote.
Sources: ISO 1207/1580 (slotted/pan head machine screws), ISO 2009, ANSI/ASME B18.6.3 (inch machine screws), DIN 84/85, GB/T 67/68/818.
