M3-1 Clinch Nut Stainless (qty x10)

Each M3 clinch nut in this bag is the -1 shank size, made of stainless steel. You get ten of them, Blue Alpine part F00115-00, for $2.50. Press one into a hole in thin sheet and the panel has a 3 mm thread that a screw can go in and out of without wearing the sheet itself.

Is it M3 or #4-40?

Small threads cause a lot of mix-ups, and these two are close enough to fool the eye. An M3 thread measures 3.0 mm over the crests with a 0.5 mm pitch. A #4-40 is about 2.84 mm (0.112 in) with 40 threads per inch, which works out to roughly 0.64 mm from one crest to the next.

Calipers will show the diameter, but the gap is only about 0.16 mm. A thread pitch gauge settles it faster. No gauge? Try a known M3 screw by hand. It should run in smoothly for several turns. A #4-40 screw in an M3 clinch nut will usually start, bind within a turn or two, and damage both threads if you keep going. The ISO metric screw thread page lists the standard pitches if you want to check other sizes.

What the -1 tells you

The number after the dash is the shank code. It’s tied to the minimum sheet thickness the nut can be installed in, and the maker pairs each code with a hole size. In the usual numbering a -1 is one of the shorter shanks, for lighter panels than a -2 or -3 of the same thread would need.

Not every M3 clinch nut is a -1, so match the code shown in your manual’s parts list. It’s the only M3 clinch nut we list. If yours shows a different dash number, ask before you order and we’ll look into it.

Pressing an M3 clinch nut

Small doesn’t mean you can tap it home with a hammer. The knurled collar has to be squeezed evenly into the sheet so the displaced metal flows into the undercut below it, all the way round. A small arbor press with flat, parallel faces is the right kind of tool. Hold the nut square, press until the shoulder is flat on the panel, and stop.

Take the hole size from the maker’s spec for that part. Margins on M3 hardware are small, and a hole a few tenths of a millimeter oversize can leave the collar without enough metal to bite.

Go easy on the screw

An M3 thread is small and shallow. A lot of trouble with an M3 clinch nut starts on the screw side: too much torque, which spins the nut out of its clinch, or a screw started at an angle. Start every screw with your fingers. On a driver, choke up on the handle so you can’t lean on it. Snug is enough.

When the M3 clinch nut thread is damaged

If a cross-threaded screw has chewed it up, chasing the thread with an M3 tap may clean it. Hold the tap straight and turn gently, because cutting torque can break the clinch loose too. A nut that already spins needs replacing. Pressing a new one into the same hole only works if the hole hasn’t grown, so measure it first.

The basics

• Type: M3 clinch nut (self-clinching, press-in)
• Thread: M3 x 0.5, metric coarse
• Shank code: -1
• Material: stainless steel
• Quantity: 10 per bag
• Blue Alpine part number: F00115-00

Stainless is the sensible material for something that lives around condensation. It’s far less likely than plain steel to rust in the hole and leave you with a seized screw.

Some people know this as an M3 PEM nut, after PennEngineering’s PEM brand. Wikipedia covers the type under swage nut. Other sizes and the screws to suit are in fasteners and tools. Questions about fit can go through the contact form, or call +1 (443) 514-5708 with your part number handy.