M2.5 Standoff 15mm F to F Brass (qty x10)

These brass standoffs are M2.5 hex spacers, 15 mm long and tapped female at both ends. A bag holds ten. Blue Alpine lists them as part number F00136-00, and the pack is $2.80.

Reading the size on M2.5 brass standoffs

Three things describe a standoff: thread, length and end style. The thread here is M2.5, so 2.5 mm nominal diameter with the usual 0.45 mm coarse pitch. The 15 mm is the brass body alone. Screw heads, washers and the board or bracket you’re holding all sit outside that number.

“F to F” means both ends are tapped holes. Neither end has a threaded stud on it. Each of these brass standoffs therefore takes two screws, one from each side, so replacing all ten means you’ll want twenty M2.5 screws on hand.

Checking the old one

Put calipers across the two flat ends. You should see close to 15 mm. Next, try an M2.5 screw in each end by hand. If it runs in smoothly for several turns, the thread matches. If it rattles around in the hole, the old part is bigger, maybe M3 or a 4-40. And if it won’t start at all, you’re probably looking at something smaller, like M2.

Hex standoffs also have an across-flats size, which decides the wrench or nut driver that fits. We don’t publish that dimension for these. If your tools depend on it, measure the old part or ask us.

Why brass standoffs

Brass machines cleanly, so internal threads come out crisp, and it conducts electricity. It won’t rust either, since it isn’t an iron alloy. Expect it to darken a little with age. That’s tarnish, and it’s cosmetic.

Conductivity cuts both ways. Plenty of circuit boards have a copper ring around each mounting hole, and brass standoffs connect that ring to whatever metal they sit on. Often that’s intended. If the spacer you’re replacing was plastic, though, someone may have wanted the board isolated at that spot, so check before you swap materials. Our nylon spacer insulates, but it’s an M4 part, 19 mm long, and won’t accept M2.5 screws.

Wikipedia’s page on brass covers the copper and zinc mix if you want the background.

Matching screws to brass standoffs

We carry two stainless M2.5 pan head screws that thread into these, one at 8 mm and one at 6 mm. Which one you need depends on how deep the tapped hole goes and how thick the part under the screw head is.

Here’s a quick way to find the usable depth. Run a screw into one end by hand until it stops. Measure how much of the shank still shows, then subtract that from the screw length. That’s how far the thread goes. Pick a screw that reaches most of that depth after passing through your board, but never all of it, or it bottoms out and the head never clamps down.

Tightening brass standoffs without stripping them

Brass standoffs are softer than the stainless screws that go into them. When something gives, it’ll be the thread inside the standoff. So hold the hex body with a nut driver, a small open-end wrench or flat-nose pliers while you turn the screw. That way the standoff can’t spin, and you aren’t relying on friction to stop it. A PH1 bit suits the pan head screws above. Snug is enough.

One habit helps on reassembly. Tighten the bottom screw first, then the top. If a standoff turns when you loosen the top screw later, the bottom one was the looser of the two. Grip the hex, back the top screw out and retighten the bottom.

Questions about these brass standoffs

Can two be stacked end to end?

Not on their own. Two female ends can’t join. You’d need a male-to-female standoff or a short threaded stud between them, and we don’t carry either.

Do you list other lengths?

No, 15 mm is the only length of brass standoffs in our range. If yours measures something else, call +1 (443) 514-5708 or use the contact form before you order, and we’ll look up the part number with you.

Where are the boards?

Under electronics. That includes the SAMD51 digital PCB board, which has no online price yet, so call or email us for a quote. Other screws, nuts and spacers live in fasteners and tools.