M4 x 12mm Flat Head T20 Torx Stainless Bolt (qty x10)

Each M4 x 12mm screw in this pack has a flat, countersunk head and a T20 Torx drive, and it’s stainless steel. Ten to a pack, Blue Alpine part F00104-00, $8.70. If your manual lists F00104-00, this is the M4 x 12mm screw it means.

How much of an M4 x 12mm screw comes out the back

Countersunk screws are measured from the top of the head, because the head disappears into the part. That makes the arithmetic simple. If the top piece is countersunk so the head sits flush, the length past its back face is 12 mm minus the thickness of that piece.

Some quick numbers. Through a 3 mm countersunk plate, about 9 mm comes out the far side. Through 5 mm, about 7. Then think about what that length has to engage. M4 coarse has a 0.7 mm pitch, so 7 mm is ten full turns. A press-in nut or a standard M4 hex nut is much shorter than that, which is why the tip often pokes out past the nut. That’s normal.

Blind holes

Going into a tapped hole that doesn’t break through? Check how deep it is. Slide a drill bit or a bit of stiff wire to the bottom and mark it with your thumb. An M4 x 12mm screw that hits the floor of the hole before the head lands will feel tight while clamping nothing, and pushing harder can strip the last few threads.

Countersinking thin material

An M4 flat head is a couple of millimeters tall. Cut a full countersink into sheet thinner than that and you go straight through, leaving a sharp ring with nothing behind it to clamp. Thin panels are often dimpled instead, with the cone pressed into the sheet rather than cut. If you’re swapping an M4 x 12mm screw that already sat flush, the hole is already prepared; just match the length.

The angle has to match, too. Metric heads like these are 90 degrees and inch flat heads are 82, and the two don’t bed down on each other evenly.

Bit, speed and galling

The drive is T20 Torx, the same as the 6 mm version and several other screws we carry, so one T20 screwdriver handles all of them. Seat it fully before you turn.

A longer stainless screw puts more thread in contact, and stainless running against stainless can gall. The surfaces grab, the screw goes stiff partway in, and forcing it can shear it off. Drive it slowly. If an M4 x 12mm screw tightens up before the head reaches the countersink, back it out, clean both threads, and try again rather than leaning on it. The screw thread article on Wikipedia explains pitch and thread form if you want the theory.

Getting an old M4 x 12mm screw out

A countersunk head sits in a cone with a lot of contact area, so one that has been in for years can be stubborn. Use a fresh T20 bit, push hard into the recess, and turn with short, firm movements. A drop of penetrating oil around the head, left for a few minutes, sometimes frees one that has sat somewhere damp. If the recess starts to round, stop and rethink before it’s gone completely.

Checking you have the right M4 x 12mm screw

• Thread: M4, 0.7 mm pitch. It should spin freely by hand into a known M4 nut.
• Length: 12 mm from the top of the head to the tip.
• Head: flat, countersunk, 90 degrees.
• Drive: six-lobe Torx recess, T20.

Still unsure? Lay the old screw next to a ruler, take a photo, and send it with your manual’s part number through the contact page. You can also reach us at +1 (443) 514-5708. More M4 hardware is under fasteners and tools.