The ULAMEX DIN 933 Metric Bolt is a hexagon head bolt with full thread, manufactured from A2 stainless steel (1.4301 / AISI 304). It is one of the most versatile fasteners in photovoltaic mounting systems, used for securing rail connections, cross connectors, profile connectors, and structural joints throughout the mounting assembly.
Technical Specifications
| Parameter | Value |
|---|---|
| Standard | DIN 933 / ISO 4017 |
| Material | A2 stainless steel (1.4301 / AISI 304) |
| Head type | Hexagon (external hex) |
| Thread | Full thread (Gewinde bis Kopf) |
| Sizes M8 | M8×20 / M8×25 / M8×30 / M8×40 mm |
| Sizes M10 | M10×20 / M10×25 / M10×30 mm |
| Spanner size M8 | 13 mm |
| Spanner size M10 | 17 mm |
| Tensile strength | ≥ 700 MPa (class 70) |
Installation Guidelines
Position the DIN 933 bolt through the component bore and thread it into the corresponding nut (DIN 934 hexagon nut or DIN 6923 flange serrated nut). Use a ring spanner or socket wrench matching the bolt size — 13 mm for M8, 17 mm for M10. Recommended torque values for PV mounting applications: M8 = 16–20 Nm, M10 = 30–35 Nm.
For profile connector and cross connector assemblies, the DIN 933 bolt passes through the connector body and into the rail channel via a hammer bolt or channel nut. Always use a calibrated torque wrench for final tightening — consistent torque ensures even clamping force across the joint and prevents aluminium profile deformation.
When pairing with DIN 6923 flange serrated nuts, the serrated bearing surface locks the connection against vibration loosening without requiring a separate washer. For standard DIN 934 hex nuts, add a DIN 125 flat washer and DIN 127 spring washer to prevent rotation under dynamic wind loads.
Applications
- Profile connectors (rail splices) — M10 bolts secure the internal splice joining two rail sections end-to-end
- Cross connectors — M10 bolts create perpendicular rail-to-rail junctions for T-shaped and grid configurations
- Structural bracket joints — M8/M10 bolts in roof hook assemblies, angle brackets, and mounting frames
- Ballast tray connections — securing flat-roof ballast system components to PV rails
- Ground-mount structures — post-to-rail and rail-to-rail connections in open-field PV arrays
Material Properties
A2 stainless steel (1.4301 / AISI 304) provides excellent atmospheric corrosion resistance for outdoor PV installations. The 18/8 chromium-nickel composition forms a self-healing passive oxide layer that protects the bolt surface across the full range of European climatic conditions — from coastal salt spray to continental freeze-thaw cycles. A2 stainless maintains full mechanical strength from −40 °C to +80 °C, covering all realistic PV operating temperatures.
The full-thread design of DIN 933 ensures that clamping force is generated along the entire bolt length, unlike DIN 931 (partial thread) where the unthreaded shank may reduce engagement in thin stack-ups. This makes DIN 933 the preferred choice for PV connector assemblies where the clamped thickness varies.
Compatibility
The ULAMEX DIN 933 hex bolt pairs with:
- PV profiles 40×40 and 80×40 — via hammer bolts or sliding nuts in the T-slot channel
- Profile connectors — internal rail splices secured with M10 bolts
- Cross connectors — perpendicular junction plates with M10 bolt holes
- Mid-clamps and end-clamps — module securing assemblies
- DIN 934 hex nuts (M8, M10), DIN 6923 flange serrated nuts (M8, M10), DIN 125 / DIN 9021 washers
Why ULAMEX
ULAMEX is an EN 1090 certified B2B wholesaler supplying complete PV mounting hardware — profiles, clamps, roof hooks, and all fasteners. One supplier, one delivery, one invoice. DIN 933 bolts are stocked in all listed sizes with bulk packaging (100, 250, 500, 1000 pcs) and pallet delivery across Europe.
Frequently Asked Questions
Q: What is the difference between DIN 933 and DIN 931?
DIN 933 has a full thread running up to the head — ideal for PV applications where the clamped stack is thin and maximum thread engagement is needed. DIN 931 has a partially threaded shank, used where shear loading on the unthreaded section is desired. For PV mounting, DIN 933 is the standard choice.
Q: Which nut type should I pair with DIN 933 bolts?
For vibration-resistant PV connections, use DIN 6923 flange serrated nuts — the serrated bearing surface locks against the clamped part without needing a separate washer. For standard connections, use DIN 934 hex nuts with DIN 125 washers.
Q: Can I use DIN 933 bolts directly in PV profile channels?
No. DIN 933 hex bolts cannot slide into T-slot channels. Use hammer bolts (T-bolts) for channel insertion. DIN 933 bolts are used for through-bolted connections with profile connectors, cross connectors, and pre-drilled mounting brackets.
Q: M8 or M10 — which size for my PV system?
Most module clamp assemblies use M8. Profile connectors and cross connectors typically require M10 for the higher clamping forces needed in structural rail joints. Check your mounting system documentation for the specified bolt size.
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