M4 x 10mm Pan Head T20 Torx Steel Bolt (qty x10)

Each M4 x 10mm screw in this pack has a pan head with a T20 Torx recess, and it’s made of steel, not stainless. You get ten for $2.50. Blue Alpine catalogs it as F00128-00.

This M4 x 10mm screw is steel, not stainless

Most of the small hardware we list is stainless. This one isn’t, and that changes a few things.

• It’s magnetic. A magnetized T20 bit will hold it, which makes one-handed starts in awkward spots much easier.
• It can rust. Steel left wet starts to corrode far sooner than stainless would. Store spares in a dry drawer, sealed bag or parts box.
• Don’t assume it’s interchangeable with a stainless M4. If you’re replacing a screw, match the part number in your manual rather than just the size.

We don’t list a stainless version of the M4 x 10mm screw. If your old one came out bright and non-magnetic, check the number before you order, or ask us.

Sizing an M4 x 10mm screw

M4 means a 4 mm nominal thread diameter. The coarse pitch for that size is 0.7 mm, so 10 mm of thread carries roughly fourteen turns. Over the threads, calipers will read slightly under 4 mm, which is normal.

Length on a pan head is taken from the flat underside of the head to the tip. The domed head doesn’t count. So this M4 x 10mm screw puts a full 10 mm into your part and the hole below it.

Mixing up M4 and M5 is the usual sizing slip. They’re close by eye. An M5 measures about 5 mm across with a 0.8 mm pitch, and an M5 nut slides loosely over an M4 thread, so a nut test tells you quickly.

The flat head M4s are measured differently

We also sell M4 x 12mm flat head screws and an M4 x 6mm flat head, both stainless and both T20. Flat (countersunk) heads are measured from the top of the head to the tip, because the head sinks into the surface. That means the 12 mm flat head doesn’t give you 2 mm more reach below the surface than this 10 mm pan head. The two end up much closer than the numbers suggest.

T20 Torx: what fits and what doesn’t

A Torx recess is a six-lobed star. Because the bit drives on the flanks of those lobes instead of on sloped walls the way a Phillips does, it has far less tendency to push itself back out as you turn. That’s why Torx tolerates more torque before it slips. It still has limits.

The sizes sit close together. A T15 will drop into a T20 recess and feel almost right, then spin and round off the lobes. A T25 won’t go in at all. If a bit wobbles when you rock it gently, it’s the wrong size or it’s worn.

Worn bits are the other cause of cam-out. Look at the tips under good light. Rounded lobe corners mean it’s time for a new one, before it ruins the M4 x 10mm screw you’re trying to remove. The Torx article on Wikipedia has a chart of the drive sizes.

One more check. If the old screw had a small pin in the center of the star, that’s a tamper-resistant Torx and needs a bit with a hole in its tip. A plain T20 can’t seat in it.

Tightening an M4 x 10mm screw

Seat the bit fully, keep it in line with the screw and push in while you turn. Stop when the head pulls down firmly. M4 is small enough that a long-handled driver can strip a tapped hole in aluminum without much effort, and a stripped hole is a bigger repair than a lost screw.

Power drivers are fine on a low clutch setting. Skip the impact driver. If an M4 x 10mm screw keeps backing out of a part that vibrates, a drop of low-strength threadlocker is a better fix than more torque.

Ordering

At $2.50 for ten, each M4 x 10mm screw costs a quarter, so a spare pack in the drawer makes sense. For thin sheet where a raised head won’t do, the M4 x 6mm flat head is the shortest M4 we carry. Not sure what you’ve got? Call +1 (443) 514-5708 with the part number or a measurement, or browse everything in fasteners and tools.