M5 Button Head Bolt A2 Stainless Steel ISO 7380

The M5 button head bolt is a low-profile stainless steel screw made to the ISO 7380 standard, combining a rounded head shape with an internal hex socket drive. It is machined from A2 stainless steel, giving it solid resistance to rust and general corrosion in ordinary workshop conditions.

This fastener suits machinists, CNC builders and small workshops who need a tidy, low-profile fixing rather than a tall hex head or a countersunk screw that requires chamfering the hole first. Because the head sits low and rounded, it works well anywhere a bulky bolt head would get in the way or catch on moving parts.

Features of the M5 button head bolt

The rounded low-profile head of the M5 button head bolt spreads load over a wider bearing surface than a countersunk Allen screw, while staying noticeably shorter than a standard hex head bolt. This makes it a practical middle ground: enough head area to hold securely, without adding unwanted height to an assembly.

A2 stainless steel is a non-magnetic, general-purpose grade that resists staining and light corrosion, though it is not the right choice for chloride-heavy or marine environments where A4 grade is usually preferred instead. The internal hex drive lets you use a standard Allen key or hex bit, even in recesses where a spanner or socket would not fit.

• Head style: rounded, low-profile button head to ISO 7380
• Material: A2 (18-8) stainless steel, non-magnetic
• Drive: internal hex socket, no external wrench flats needed
• Thread: M5 metric, standard coarse pitch
• Finish: bright stainless, no plating required

Where it’s used

The M5 button head bolt is common in CNC router and mill assembly, where its low head clears linear guides, belts and moving carriages without interference. It also turns up on T-slot aluminium profile frames, enclosure panels and machine guards, wherever a visible bolt head needs to sit flush and neat rather than proud and bulky.

It is equally useful outside CNC work, on brackets, jigs and general metal fabrication where stainless hardware is specified for its finish and corrosion resistance. For the fuller range of fasteners and CNC hardware carried alongside this size, see the CNC parts shop.

What to check before buying

Confirm the thread pitch and length you need before ordering an M5 button head bolt, since M5 is a common size but is sold in several lengths, and the wrong one will either bottom out in a blind hole or leave too little thread engagement. Check that the mating hole or nut is also metric M5 and not a close imperial size, as a fastener that threads in loosely will strip under load.

Match the Allen key size to the bolt: this size normally takes a 3mm hex key, and forcing a worn or slightly wrong-size key rounds out the socket quickly. If the application is structural rather than decorative, check whether a higher tensile fastener suits the job better, since A2 stainless is not rated as high as alloy steel grades.

Installation and maintenance

Drive the M5 button head bolt with a properly fitting hex key seated fully in the socket, applying steady, even torque rather than sudden force, since stainless threads can gall if over-tightened or rushed. A light smear of anti-seize or thread lubricant reduces the risk of galling, particularly when the bolt is driven into a stainless or aluminium tapped hole.

Stainless fasteners need little ongoing maintenance beyond an occasional check for loosening from vibration, and they do not require the periodic re-oiling that carbon steel hardware does. For background on the thread standard this size follows, see the ISO metric screw thread reference.

FAQ

What size Allen key fits an M5 button head bolt? A 3mm hex key is the standard fit for this size and head style.

Can it be used outdoors? A2 stainless copes with normal weather, but for saltwater, chlorine or heavy chemical exposure an A4 grade fastener is the safer choice.

How is a button head different from a socket cap head? The button head is lower and more rounded for a neater fit in tight spaces, while a socket cap head is taller and cylindrical, giving it a higher load rating.