A guide to coach to coach bolts and what they are used for.
What are coach bolts?
Coach bolts, also known as carriage bolts or cup square hex are a type of threaded bolt designed for use in primarily in wood but often used in plastics and metal . In particular, they are intended to be used for fastening wood to wood or wood to metal.
Carriage bolts feature a shallow domed (mushroom) head. The large head shape has various uses – to provide a fixing you can tighten from one side, give an attractive smooth finish for visual effect and prevent entanglement.
The head also acts as security feature as can only be undone from one side.
What are coach bolts used for?
Mainly used in wood to wood connections but can be used in plastics and steel.
Used where access to tighten is difficult from both sides.
Used as a security fixing where it cannot be removed with any tool from the head. Also can be used with security nuts such as shear nuts to increase security.
Landscape work such as sleepers, retaining walls etc
Playgrounds where to head needs to be smooth to prevent entanglement.
What is the difference between coach bolts and coach screws?
We often get asked for coach bolts when people mean coach screws. Coach screws are a type of wood screw but with a hexagon head often referred to as lag screws.
What material do coach bolts come in?
Mild steel or high tensile steel which can be plated in zinc, black, silver,green or hot dipped galvanised.
Stainless steel in A2 or A4.
Brass / Bronze upon request.
What standards are coach bolts made to?
Manufactured to Din 603 / 555 (555 being the nut)
What sizes are coach bolt available in?
We stock a massive range of diameters and sizes available to buy online or if not shown can be sourced or made;
Diameters from M5 up to M30
Lengths of 12mm up to 600mm – longer sizes on request.
| Zinc Plated Bolts | |||
 M5 | M6 | M8 | M10 |
| Sizes upon request | 20mm up to 150mm | 20mm up to 200mm | 25mm up to 300mm |
M12 | M16 | M20 |  |
| 25mm up to 350mm | 100mm up to 200mm | Sizes upon request |