M5 x 12mm Flat Head T20 Torx Stainless Bolt (qty x10)

This pack holds ten stainless M5 flat head screws, 12 mm long, with a T20 Torx drive: Blue Alpine part F00106-00, $9.43 for the ten. What trips people up with this M5 x 12mm screw usually isn’t the thread or the length. It’s the bit.

Three M5 flat heads, two bit sizes

We carry M5 countersunk screws in three lengths, and they don’t all take the same driver.

• M5 x 8 mm countersunk: T25 Torx
• M5 x 12mm screw, flat head (this page): T20 Torx
• M5 x 20 mm flat head: T20 Torx

M5 countersunk screws commonly take a T25, so it’s easy to reach for that bit out of habit. It won’t fit a T20 recess. The other way round, a T20 bit in a T25 head spins and strips it. Go by the drive size on the listing rather than the thread size, and keep both bits handy if you’re working with mixed hardware.

Telling an M5 from a #10-32

This is the classic near-miss. M5 coarse has a 0.8 mm pitch. The inch size #10-32 has 32 threads per inch, about 0.79 mm, so the pitch is almost identical. The diameters differ: 5.0 mm for M5 against roughly 4.83 mm (0.190 in) for a #10. A #10-32 screw will usually run into an M5 nut and feel loose. An M5 x 12mm screw forced into a #10-32 thread will bind and damage it.

Calipers across the crests settle it. Five millimeters is M5. A reading near 4.8 means inch hardware. If the threads look noticeably coarser, it may be #10-24, which works out to about 1.06 mm pitch.

Length check on an M5 x 12mm screw

Countersunk length includes the head. Put the caliper jaws on the flat top and on the tip. Twelve millimeters is this part. A reading of 8 or 20 means one of the others. You can also just hold the old screw against a new one. The three lengths are far enough apart to tell by eye side by side.

What an M5 x 12mm screw threads into

Any M5 x 0.8 thread. In sheet metal that’s often a press-in nut like the M5-3 above. Where you can reach the back of a plate, a plain M5 hex nut does the job.

Leave the washer off the head end. A countersunk head needs its cone to seat, and a flat washer under it holds the head up and spoils the flush finish. The M5 washers go on the nut side if you use them at all.

Reuse or replace?

A stainless M5 x 12mm screw that came out clean can normally go back in. Fit a new one if any of these apply:

• The T20 recess is rounded or the lobes look smeared.
• The threads have flattened crests or bright, torn patches, which is what galling leaves behind.
• The shank is bent, even slightly. Roll it on a flat surface to check.
• It took far more effort to remove than the others did.

With ten in a pack, it’s often simpler to put fresh screws in every hole than to mix old and new.

Driving an M5 x 12mm screw with a T20

A T20 recess is on the small side for an M5 head, so the bit carries a lot of torque for its size. Push it all the way in and keep steady pressure. Skip the impact driver. Turn slowly, too, especially stainless into stainless, where fast driving invites galling. Seat the head in its countersink and stop.

Our T20 screwdriver fits these. If you’re curious how Torx compares with hex, Phillips and the rest, Wikipedia keeps a list of screw drives with drawings.

Not sure which of the three M5 flat heads your machine uses? Give us the part number from your manual’s parts list through the contact page, or call +1 (443) 514-5708.