The ULAMEX Hammer Bolt (T-Bolt) is a specially shaped fastener manufactured from A2 stainless steel (1.4301 / AISI 304), designed to slide into the T-slot channel of PV mounting profiles. Its T-shaped head inserts through the channel opening, then locks in place with a 90-degree rotation — creating a secure, adjustable anchor point for module clamps, cable clips, cross connectors, and other rail-mounted components.
Technical Specifications
| Parameter | Value |
|---|---|
| Material | A2 stainless steel (1.4301 / AISI 304) |
| Head type | Hammer head (T-shaped) |
| Drive | External hexagon |
| Sizes M8 | M8×20 / M8×25 mm |
| Sizes M10 | M10×25 / M10×30 mm |
| Spanner size M8 | 13 mm |
| Spanner size M10 | 17 mm |
| Channel compatibility | 40×40 mm and 80×40 mm ULAMEX PV profiles |
| Tensile strength | ≥ 700 MPa (class 70) |
Installation Guidelines
To install, orient the T-shaped head parallel to the profile channel slot and slide it in from the open end of the rail, or insert it at any point along the channel where the slot width permits. Once positioned at the desired location, rotate the bolt 90 degrees so the T-head engages perpendicular to the slot — this locks the bolt against pull-out and creates a secure mounting point.
Thread the desired component (clamp, connector, or bracket) onto the bolt shaft and hand-tighten. Final torque should be applied with a calibrated torque wrench: M8 = 16–20 Nm, M10 = 30–35 Nm. Over-tightening risks deforming the aluminium profile channel walls; under-tightening allows the component to slide or rotate under wind load.
For pre-assembled rail sections, insert all required T-bolts before mounting the rail on the roof structure — this avoids the need to feed bolts from the rail ends after installation. Mark bolt positions along the rail with a measuring tape to ensure correct module spacing before final tightening.
Applications
- Module mid-clamps and end-clamps — primary attachment of solar panels to mounting rails; M8 T-bolts are the standard for most clamp assemblies
- Cross connectors — creating perpendicular rail junctions in grid-pattern arrays
- Profile connectors — through-bolted rail splices securing internal connector bodies
- Cable clips — anchoring stainless steel DC cable routing clips to the profile channel
- Grounding assemblies — securing grounding plates and earthing connectors to the rail
- Adjustable module positioning — T-bolts allow stepless horizontal positioning of clamps along the full rail length before tightening
Material Properties
A2 stainless steel (1.4301 / AISI 304) is the standard material for PV T-bolts, combining corrosion resistance with the mechanical strength required for secure module fastening. The austenitic microstructure provides ductility that prevents brittle fracture under shock loads (e.g., wind gusts) while maintaining stable clamping force over decades of thermal cycling.
The T-head geometry is precision-formed to match the internal channel dimensions of standard PV mounting profiles. The head width is calibrated to pass through the channel slot opening but lock securely behind the slot lips when rotated, providing pull-out resistance that exceeds the bolt’s tensile capacity.
Compatibility
The ULAMEX hammer bolt is designed for use with:
- ULAMEX PV profiles 40×40 and 80×40 — aluminium mounting rails with T-slot channels
- Mid-clamps and end-clamps — solar module securing clamps
- Cross connectors and profile connectors — structural rail junction components
- Cable clips — DC cable management clips
- Grounding plates — equipment bonding components
- DIN 934 hex nuts, DIN 6923 flange serrated nuts — pairing nuts for clamp assemblies
Why ULAMEX
ULAMEX is an EN 1090 certified B2B wholesaler supplying the complete PV mounting system. T-bolts are stocked alongside profiles, clamps, roof hooks, and PV triangles — one order covers the full fastener requirement. Available in bulk packaging (100, 250, 500, 1000 pcs) with pallet delivery across Europe.
Frequently Asked Questions
Q: What is the difference between a hammer bolt and a standard hex bolt?
A hammer bolt (T-bolt) has a specially shaped T-head that slides into the T-slot channel of PV mounting profiles, allowing stepless positioning along the rail. A standard hex bolt (DIN 933) requires a pre-drilled hole or a separate channel nut. T-bolts are the primary fastener for mounting clamps and accessories on PV rails.
Q: M8 or M10 T-bolts — when to use which?
M8 T-bolts are standard for module clamp assemblies (mid-clamps and end-clamps). M10 T-bolts are used for heavier-duty connections such as cross connectors, profile connectors, and structural joints where higher clamping force is required.
Q: Can T-bolts be inserted after the rail is already mounted?
Yes, T-bolts can be inserted from either open end of the rail. However, it is faster and more practical to pre-load all T-bolts into the profile before mounting it on the roof structure. For mid-rail insertion, you can also slide the bolt in from an open rail end and reposition it along the channel.
Q: What torque should I apply to PV T-bolts?
Recommended torque: M8 = 16–20 Nm, M10 = 30–35 Nm. Always use a calibrated torque wrench. Over-tightening deforms the aluminium profile channel; under-tightening risks module displacement under wind load.
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