M2.5 x 6mm Pan Head Philips Stainless Screw (qty x10)

This is the M2.5 x 6mm pan head screw in stainless steel, with a Phillips drive. Ten come in each pack for $2.50. Blue Alpine’s part number is F00110-00.

Is an M2.5 x 6mm screw long enough?

Usually, for thin parts. The 6 mm is measured from under the head to the tip, and all of it is available for passing through your part and biting into the thread below. What’s left after the part is your thread engagement.

A common shop rule is at least one screw diameter of engagement in steel and more in softer metals like brass or aluminum. For M2.5 that means 2.5 mm minimum. With a 0.45 mm pitch, 2.5 mm works out to about five and a half turns of thread.

Running the numbers

• Through a standard 1.6 mm circuit board: 4.4 mm left, close to ten full turns. Plenty.
• Through a 3 mm bracket: 3 mm left. Fine in steel, getting thin in brass.
• Through anything over about 3.5 mm: you’re below one diameter. Go to the 8 mm screw.

Add any washer to the thickness, too. People forget it, and a 0.5 mm washer turns a comfortable stack into a marginal one.

M2.5 x 6mm or a #2-56?

This is the lookalike that catches people. A #2-56 machine screw has 56 threads per inch, which is about 0.454 mm per turn, almost exactly the M2.5 pitch. But it measures only about 2.2 mm across the threads. Drop one into an M2.5 hole and it will start, feel vaguely right, then strip as soon as you tighten it. Going the other way, an M2.5 x 6mm screw in a #2-56 hole either won’t start or binds almost at once.

Calipers settle it. An M2.5 reads a hair under 2.5 mm over the threads. Anything near 2.2 mm is the imperial screw.

When shorter is the better choice

An M2.5 x 6mm screw earns its place in shallow tapped holes. A screw that’s too long hits the bottom of a blind hole before the head reaches the surface. It feels tight. It isn’t clamping anything. You’ll find out later when the part rattles.

To check a blind hole, run a screw in by hand until it stops, note how much shank still shows, and work out the depth. Then pick the length that leaves a little room at the bottom.

Those standoffs are threaded at both ends, so each one needs a pair of screws. Stainless on brass is a friendly combination. Galling, where threads seize partway in, is mostly a stainless-on-stainless problem.

Driving an M2.5 x 6mm Phillips screw

Use a PH1 bit on the M2.5 x 6mm. The trap is Pozidriv. A PZ1 looks almost the same at a glance, but it has extra ribs between the main blades, and in a Phillips recess it sits shallow and climbs out under load. Look at the bit before you start: a PZ has a second, smaller set of ribs between the four main blades, and it’s usually stamped PZ. The list of screw drives on Wikipedia has clear drawings of both.

Many stainless screws are only weakly magnetic, so don’t count on a magnetic bit to hold one. Two tricks work:

• Push the screw through a small square of masking tape, then press the tape onto the bit.
• Start it with tweezers or fingers, then bring the driver in once the thread has caught.

And put something soft under the work. A screw this small that falls into a cabinet can take longer to find than the job itself.

Spares and part numbers

We list the M2.5 x 6mm screw as F00110-00, and the longer one as F00130-00. If your parts list shows a different number, or you can’t tell which length came out, send us the number through the support page and we’ll match it. Screws this size are common on circuit boards in general; our buffer PCB board and other electronics are listed separately. The rest of the small hardware is in fasteners and tools.