Can I use a M3 screw in a M4 hole?

No. M3 is 3.0 mm with a 0.5 mm pitch and M4 is 4.0 mm with a 0.7 mm pitch. The smaller screw will spin loose and the larger one will cut new threads and ruin the hole.

What is the difference between M3 and M4?

1.0 mm of thread diameter, different pitches (0.5 mm vs 0.7 mm), different tap drills (2.5 mm vs 3.3 mm) and different head sizes.

M3 vs M4

They differ by 1.0 mm across the threads — enough that they are never interchangeable, but little enough that they are easy to mix up in a parts tray.

	M3	M4
Thread diameter	3.00 mm	4.00 mm
Standard pitch	0.5 mm	0.7 mm
Tap drill	2.5 mm	3.3 mm
Clearance hole	3.4 mm	4.5 mm
Cap head Ø	5.5 mm	7 mm
Hex key	2.5 mm	3.0 mm
Torque into steel	80-130 N·cm	2.0-3.0 N·m
Into plastic	35-60 N·cm	0.8-1.4 N·m

M3 is normally used for

PC cases, 2.5in drives, 3D printers, extrusion hardware, DIN-rail devices, robotics

Everything M3 fits →

M4 is normally used for

Rack panels and cage nuts, monitors, VESA 75/100 plates, machine covers, e-bike parts

Everything M4 fits →

If you are not sure which one you have

Measure across the outside of the threads with a caliper. A reading within about 0.1 mm of the nominal size is your answer — 3.0 mm means M3, 4.0 mm means M4.

Use the screw size finder →

Buy these screws at TechSpare Warehouse

In stock and shipped from South Carolina. Our black screws are Phillips wafer head (low profile); match the head style and length to the original before you order.

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M3 vs M4

If you are not sure which one you have

Buy these screws at TechSpare Warehouse

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