M4 Stainless Button Screw ISO 7380 A2 Socket Head

The M4 stainless button screw is a low, round-head socket screw made to the ISO 7380 standard, built for jobs where a neat finish matters as much as strength. Machined from A2 stainless steel, it resists moisture and mild chemical exposure far better than a plain zinc-plated screw, making it a common choice on CNC machines, extruded aluminium frames, and general metalwork.

Because the head sits low and rounded rather than tall and hexagonal, this screw suits joints where the fastener stays visible after assembly — enclosure panels, guide rails, brackets, and any spot where a bulky hex head would look out of place. The M4 size covers light to medium-duty joints, and the internal hex drive lets you apply real torque even in recessed or narrow pockets.

Features of the M4 stainless button screw

Every screw in this listing is manufactured to ISO 7380 tolerances, so head diameter, socket size, and thread pitch stay consistent and match any standard metric hex key. A2 stainless, roughly equivalent to 304-grade, resists rust and surface staining without the cost of higher alloy grades.

The rounded, low-profile head spreads clamping load over a wider bearing surface than a countersunk screw, while staying short enough to avoid interference with adjacent parts — a practical shape for joints that get assembled and taken apart repeatedly.

• Head type: low round button head per ISO 7380
• Drive: internal hexagon, Allen key
• Thread: M4 metric
• Material: A2 stainless steel
• Corrosion resistance suited to damp or lightly exposed environments
• Fits standard metric hex keys

Where it’s used

The M4 stainless button screw turns up wherever a fastener needs to stay strong and unobtrusive. On CNC routers and mills, it secures covers, cable guides, limit switch brackets, and gantry panels — spots where a protruding hex head could snag a cable or interfere with travel. It also fits well in aluminium extrusion assemblies, holding panels, corner brackets, and mounting plates without adding bulk to the profile.

Outside CNC work, it’s used in enclosure boxes, sheet metal housings, and general workshop fixtures where appearance and corrosion resistance both matter. For the full range of CNC hardware and machine parts, browse the CNC parts shop.

What to check before buying

Confirm the thread length you need before ordering — a screw that’s too long will bottom out or protrude through the joint, while one too short won’t engage enough thread. Check the hex key size required too, since a worn or wrong-size key can round out the drive on M4 hardware.

If the M4 stainless button screw pairs with a nut or tapped hole, make sure the mating thread is also metric M4, since mixing metric and imperial threads is a common mistake. For structural joints, check that A2 stainless meets the strength class required; where higher tensile strength is the priority, a graded steel screw may suit the job better than stainless.

Installation and maintenance

Drive the M4 stainless button screw with a correctly sized hex key, going in straight to avoid cross-threading. Snug it to a firm hand-tight torque; A2 stainless can gall — its threads can seize — if overtightened dry, so a touch of anti-seize or light lubricant on the threads helps on joints that get assembled often.

Stainless fasteners need little upkeep beyond periodic checks for loosening from vibration on moving machine assemblies. For background on stainless steel grades and how A2 compares with other alloys, see the Wikipedia entry on stainless steel.

FAQ

What hex key size fits the M4 stainless button screw? A 2.5mm hex key fits the ISO 7380 M4 socket head.

Is A2 stainless strong enough for structural joints? It gives good corrosion resistance but lower tensile strength than graded alloy steel, so check the load rating first.

Can this screw be used with aluminium extrusion T-nuts? Yes, as long as the T-nut thread is also metric M4.