Bolts
Bolts are for fixings that need proper clamping force through timber, steel, brackets and plant, where screws just are not enough on site.
When you're bolting posts, fixing steelwork, hanging heavy brackets or pulling timber sections tight, get the right bolt for the job. Hex head bolts suit spanners and sockets for solid tightening, while carriage bolts are the better shout where you want a neat dome head and less spin in timber. Check bolt sizes properly, match the nut and washer, and do not guess on grade if the fixing is taking load.
What Are Bolts Used For?
- Fixing timber posts, sleepers and structural sections where a screw will not give enough pull-through strength or long-term clamping force.
- Joining steel brackets, channels and plates on gates, plant mounts, framework and general site fabrication where hex head bolts can be tightened down hard with a spanner or socket.
- Bolting through timber fencing, sheds, benches and outdoor joinery with carriage bolts where the domed head leaves a cleaner finish and the square neck bites in to stop the bolt spinning.
- Replacing worn or missing fixings on machinery guards, trailers, workbenches and site storage where matching the correct thread, length and grade saves a lot of grief later.
- Securing heavy fixtures with m8 bolts or m10 bolts where load, hole size and material thickness all need to line up properly for a safe, tight fit.
Choosing the Right Bolts
Sorting the right bolt is simple: match it to the material, the load, and how you are tightening it. Do not just grab whatever fits the hole.
1. Hex Head or Carriage Bolt
If you are fixing steel, brackets or anything you need to torque up properly, go with hex head bolts. If you are bolting through timber and want a smooth finished head that will not easily turn while tightening, carriage bolts are usually the better option.
2. Size and Length
Do not undersize just because it is easier to drill. M8 bolts are common for lighter brackets and general fixing, while m10 bolts are a safer bet where the joint is taking more load or the sections are thicker. Make sure there is enough length to pass through both materials, plus the washer and full nut engagement.
3. Finish for the Environment
For outside timber, fencing and exposed metalwork, galvanised bolts make more sense than plain finished fixings. If the job is in wet areas, washdown zones or coastal conditions, stainless steel bolts are worth paying for, but do not assume they are always stronger.
4. Grade Matters
If the bolt is doing more than just holding a cover plate on, check the grade. High tensile bolts such as 8.8 are the ones for heavier clamping and structural type jobs. For basic light-duty fixing, over-speccing is not always needed, but under-speccing will come back to bite you.
Who Uses These Bolts?
- Chippies and landscapers use carriage bolts for timber frames, sleepers, pergolas and fencing because they pull sections together neatly without chewing up the face of the timber.
- Steel erectors, fabricators and maintenance fitters reach for hex head bolts when joining brackets, plates and framework that need proper torque and easy removal later.
- Groundworkers and site teams keep common bolt sizes on hand for fixing plant guards, gate hardware, shuttering components and temporary works that take knocks all week.
- Farm, yard and workshop users swear by galvanised bolts for outdoor kit and stainless steel bolts where weather and washdown would soon rust plain fixings out.
Bolt Fixings That Save Time on Site
Get the supporting bits right and bolting up is quicker, tighter and far less annoying.
1. Nuts
Do not get caught with the right bolts and no way to clamp them. Matching Nuts to the thread and grade stops wasted trips back to the van and makes sure the fixing actually goes together properly.
2. Washers
A decent washer spreads load, protects the surface and helps stop the nut pulling into softer timber or thin metal. Keep a stock of Washers handy, especially when you are tightening into timber or oversized holes.
3. Power Tool Socket Sets
If you are running up repeat fixings, a proper Power Tool Socket Sets setup saves your wrists and speeds the whole job up. It is the difference between spinning fixings in cleanly and fighting rounded heads with the wrong socket.
Choose the Right Bolts for the Job
Use this as a quick guide before you fill the basket.
| Your Job | Bolts or Type | Key Features |
|---|---|---|
| Fixing timber posts, sleepers or fencing rails | Carriage bolts | Domed head for a cleaner finish, square neck to resist spinning, good pull-through with washers |
| Joining steel brackets, plates or channels | Hex head bolts | Easy to tighten with spanners or sockets, better for higher torque, suits workshop and site fitting |
| Outdoor fixings exposed to weather | Galvanised bolts | Corrosion resistance for gates, fencing, external brackets and general outside work |
| Wet areas or washdown environments | Stainless steel bolts | Better corrosion resistance where rust is a real issue, cleaner finish, good for long-term exposure |
| Load-bearing or harder-worked connections | High tensile bolts | Higher strength grades such as 8.8, better suited to clamping force and tougher mechanical fixing jobs |
Common Buying and Usage Mistakes
- Buying by length alone and ignoring diameter is a standard mistake. A bolt that is long enough but too thin will flex, loosen or fail early, so always match the diameter to the load and hole size.
- Using stainless steel bolts and assuming they are stronger than galvanised ones catches plenty of people out. Stainless is often chosen for corrosion resistance, not outright strength, so check the grade before using it on harder-worked fixings.
- Leaving washers out to save a few quid usually ends with damaged timber faces, pulled holes or fixings that work loose. Use washers where the load needs spreading or the hole is oversized.
- Mixing up bolts with Set Screws leads to wrong ordering and awkward fitting. If the job needs a nut on the far side, buy a proper bolt and matching nut rather than hoping a partially threaded fixing will sort itself out.
- Guessing the grade on loaded fixings is asking for trouble. If the joint is structural, mechanical or taking repeated strain, confirm whether you need high tensile bolts rather than basic general-purpose fixings.
Hex Head Bolts vs Carriage Bolts vs Set Screws
Hex Head Bolts
These are the usual pick for steelwork, brackets and heavier fixings where you want solid tightening with a spanner or socket. They are easier to torque up properly than carriage bolts and make more sense where appearance matters less than access and clamping force.
Carriage Bolts
Best for timber jobs where you want a smooth, rounded head on the visible side and a fixing that will not easily spin once the square neck bites in. They are less handy if you need to keep adjusting the fixing in steel or awkward tight spots.
Set Screws
These are usually fully threaded and useful where full thread engagement matters across the whole grip length. For the wider range, have a look at Nuts, Bolts & Washers if you are still deciding what suits the fixing best.
Maintenance and Care
Keep Threads Clean
Dirty threads full of grit, paint or zinc burrs make nuts bind and give false torque. Brush threads off before fitting, especially on site-stored fixings that have been rolling around in a box.
Store by Size and Type
Mixing m8 bolts, m10 bolts and different finishes in one tub is how jobs get slowed down. Sort fixings by diameter, length and finish so you are not trial-and-error fitting every time.
Watch for Rust and Damage
If the threads are damaged, the head is rounded or the coating has badly broken down, bin it. Reusing battered bolts on anything important is false economy and usually ends in stripped nuts or seized fixings.
Use the Right Tightening Gear
Poor-fitting spanners and worn sockets round heads off quickly. Use the correct size and keep your sockets in decent nick so you can tighten properly without chewing through fixings.
Why Shop for Bolts at ITS?
Whether you need a handful of carriage bolts for a timber repair or boxes of hex head bolts in common bolt sizes for site stock, we have the range ready to go. That includes m8 bolts, m10 bolts, stainless steel bolts, galvanised bolts and more, all held in our own warehouse for next day delivery.
Bolts FAQs
What's the difference between a bolt and a set screw?
A bolt is normally used with a nut to clamp materials together through a clearance hole. A set screw is usually fully threaded and can be used in threaded components or with a nut depending on the job. In plain site terms, if you are passing through timber or steel and tightening with a nut on the back, you are usually looking for a bolt.
What bolt size do I need for timber fixing?
It depends on the load, the timber thickness and the size of the parts you are joining. For lighter brackets and general timber work, m8 bolts are common. For posts, structural timber joints and heavier outdoor fixings, m10 bolts are often the safer choice. Use washers and make sure the bolt is long enough to give full nut engagement.
What does the grade (8.8) on a bolt mean?
That marking shows the bolt strength class. Grade 8.8 is a common high tensile bolt used where the fixing needs more clamping force and strength than basic general-purpose bolts. If the joint is taking load, vibration or repeated strain, do not ignore the grade marking.
Are stainless steel bolts stronger than galvanised?
Not always. Stainless steel bolts are often chosen for corrosion resistance, especially outside or in wet conditions, but that does not automatically make them stronger. Galvanised bolts are usually picked for outdoor durability at sensible cost. Always check the actual grade and application instead of assuming by finish alone.
What's the difference between a carriage bolt and a hex bolt?
A carriage bolt has a smooth domed head and a square section under the head that bites into timber to stop it spinning. A hex bolt has a six-sided head for tightening with a spanner or socket. Carriage bolts are better for timber and visible faces, while hex head bolts are better where access, torque and adjustment matter more.
