ST5.5 self-tapping screws
sheet-metal (ISO 1478)
5 documented uses, taken from manufacturer catalogs, service manuals and teardowns.
Pilot hole
4.8-5.1 mm in 1.5-3.0 mm steel
Too tight and the head snaps or the boss splits; too loose and the thread strips on the first removal.
Buy ST5.5 self-tapping screws
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Watch out for
- High driving torque required; impact drivers are recommended for lengths >50 mm.
- Most TV, appliance, HVAC and power-tool service documents list only a driver type or a part number, never a thread size - so a screw kit sold as 'fits brand X' is usually a seller's guess, not an OEM spec. Measure the old screw before buying.
Where ST5.5 is used
SL Rack Solar Mounting
Fastening PV rails to trapezoidal sheet metal roofs
20-25 mm · confirmed · signage
View sourceS-5! PVKIT 2.0
Securing PV clamps to standing seam roof brackets
25 mm · confirmed · metal brackets
View sourceOptonica Solar Screws
General PV racking and signage mounting on metal
25 mm · confirmed · signage
View sourceUNITEK Steel Structure
Fixing roof/wall envelopes to thick purlins
32 mm · confirmed · metal brackets
View sourceSolar Panel Racking (mg-solar)
Direct attachment of mounting brackets to metal roof ribs
25 mm · confirmed · signage
View source