STAINLESS STEEL SLOTTED HEXAGON HEAD SET SCREWS DIN 933SZ

Slotted Hexagon Head Set Screws DIN 933SZ — Take the familiar DIN 933 fully threaded hex screw and machine a screwdriver slot across the top of the head, and you get a fastener that can be driven two ways: started, or finished, with a flat-blade screwdriver where there isn't room to swing a spanner, or turned conventionally with a spanner or socket where access allows. That flexibility makes it a regular choice in electrical enclosure and earthing or bonding connections, gas and plumbing fittings, panel work in confined equipment, and any joint where a visible witness mark or the option to pass locking wire through the slot adds a useful layer of tamper or vibration security. Everything about the underlying fastener — head size, thread length, full-thread profile — still follows DIN 933, so it behaves like a standard fully threaded hex screw in every respect except the drive option; the slot is a genuinely additional feature rather than a different fastener family. Grade guidance follows the same logic as other general-purpose stainless fixings: A2 is more than adequate for indoor electrical, gas, and plumbing work in typical building environments, while A4 becomes worthwhile in outdoor enclosures, coastal installations, or process environments with washdown or chemical exposure, where the combination of a slotted head (often in confined, hard-to-inspect locations) and a corrosive atmosphere makes the extra resistance to pitting worth paying for. Sizing follows the same rules as any fully threaded hex screw: diameter and length should be chosen for the load and the tapped hole or nut being used, with enough thread engaged in the mating material to develop the fastener's rated strength. Where spanner access is unrestricted and the slot's locking-wire feature isn't needed, a standard DIN 933 or ISO 4017 hex screw without the slot is the simpler and marginally more economical specification.

FAQs
Does the slot weaken the head or reduce the screw's rated strength?
The slot removes a small amount of material from the head, but the fastener still carries its rated strength grade as a hexagon-driven screw; the slot is a secondary drive and locking feature rather than part of the primary load path, though highly load-critical applications should confirm this against the specific manufacturer's range.

Can locking wire really be passed through the slot on a hexagon head?
Yes — the slot gives a straight channel across the head that wire can be threaded through and twisted to another fixing point, providing a visual tamper check and some resistance to the screw backing out, a feature a plain hexagon head doesn't offer.

Is this the same as a hexagon socket or hexalobular screw?
No — those describe internal drive recesses machined into the top of the head; this fastener retains its full external hexagon for spanner or socket use, with the slot added purely as a secondary screwdriver option across the top face.

When would I choose this over a plain DIN 933 or ISO 4017 screw?
Choose it specifically where spanner access is restricted, where a screwdriver is the only practical tool, or where the locking-wire option is wanted; otherwise a plain hexagon head screw is the simpler and slightly more economical choice.