It bites or seats into compatible material to resist rotation while the nut is tightened. The hole and material must support that action.
Smooth Head Bolts for Timber and Assembly Work
Carriage Bolts create bolted joints with a smooth domed head and a square neck that resists rotation in compatible material. MacBlair groups this range within nuts, bolts and threaded fixings, making it easier to match the product to the wider task. Choose diameter, length, thread, grade and finish for the material stack and exposure. The square neck needs an accurately prepared seat, while the nut and washer arrangement on the opposite side completes the connection.
Clamp components, mark the hole and drill square at the stated clearance. Insert the bolt from the side where the smooth head is required and seat the neck without splitting or excessively crushing the material. For the next stage, nuts for carriage bolts can support a related part of the job. Fit the specified washer and nut, then tighten from the threaded side while keeping the head fully seated.
Carriage Bolts should be used with the material, load and working conditions in mind. Do not hammer an oversized neck into weak timber or substitute a carriage bolt in a structural joint without checking the design. Edge distance, grain direction, metal thickness and corrosion exposure all affect performance. washers for the threaded side may also be useful where the task extends beyond this category.
Protect the domed head and threads from impact, keep matching nuts with the correct size and replace bolts with distorted necks. Check ratings, fixings, working parts or material condition before reuse, and remove damaged items from service. drills for aligned holes helps complete the surrounding work without substituting one product for another. Inspect both sides after tightening, confirming that the neck has not spun and the head remains flush without pulling too deeply into the surface.
Carriage Bolts FAQs
Insert the smooth domed head from the side where a low-profile finish is wanted, with the nut on the accessible threaded side.
Product conventions may measure from beneath or include the head depending on the standard. Check the supplier diagram and allow for materials, washer, nut and engagement.
Use the washer arrangement specified, commonly beneath the nut to spread bearing load. Match its size and material to the bolt and joint.
The square neck may not be seated, the hole may be oversized or the material may be damaged. Stop tightening and correct the connection rather than gripping the smooth head destructively.