Mushroom head square neck bolt to DIN 603 / ISO 8677, supplied with a hex nut. The square neck beds into the material and stops the bolt turning, so it is tightened from the nut side only.
Prices on request. Contact us for availability and quotations.
Known in the local trade as a garage bolt, this is a carriage or coach bolt: a domed mushroom head with no drive recess, a square section beneath the head, and a threaded shank. The square neck pulls into timber or through a square hole in steel and locks the bolt against rotation, so the joint is tightened entirely from the nut. The smooth head leaves nothing to grip on the exposed face.
DIN 603, published internationally as ISO 8677, fixes the head and neck geometry. Bolts are made in property classes 4.6, 4.8 and 8.8 and supplied self-colour, black, bright zinc plated or hot-dip galvanised. Under ISO 898-1, class 4.6 is 400 MPa nominal tensile with 240 MPa yield, class 4.8 is 400 MPa nominal with a 310 MPa proof stress, and class 8.8 is 800 MPa tensile with 640 MPa yield up to 16 mm diameter.
Typical use is on gates, doors, roller shutters and garage door hardware, timber frames and fencing, and on sheet steel panels where a tamper-resistant, snag-free head is wanted on the outside face. In coastal or outdoor positions, hot-dip galvanised or stainless bolts should be specified; a galvanised bolt requires the matching over-tapped galvanised nut.
When ordering, state the thread size and length, the property class, the finish, and whether the nut and washer are to be supplied with the bolt. Check the square neck dimension against the hole or the timber thickness for the size chosen.
| Standard | DIN 603 / ISO 8677 - mushroom head square neck bolts (carriage / cup square bolts) |
|---|---|
| Head and Neck Form | Domed head with no drive recess over a square neck that beds into the material and prevents the bolt turning when the nut is tightened |
| Property Classes | 4.6, 4.8 and 8.8 |
| Strength by Class | 4.6: 400 MPa nominal tensile, 240 MPa yield. 4.8: 400 MPa nominal tensile, 310 MPa proof stress. 8.8: 800 MPa tensile, 640 MPa yield (d ≤ 16 mm) |
| Finishes | Self-colour, black, bright zinc plated or hot-dip galvanised |
| Supplied With | Hexagon nut (ISO 4032 form) as photographed |
