Bolts are designed to be used with pre-drilled holes and nuts to tighten the fixing. These types of mechanical fasteners can have a thread that runs the full length of the shaft or partially. Combining these with washers allows the tension to be spread over the fixed materials when tightening and fixing in place.
Benefits of bolts
The benefits of bolting parts together mean you can unscrew them whenever you need, unlike rivets which become a permanent fixing.
Stainless steel bolts are very effective when joining external materials where rusting may be an issue. It can be advisable to use the partially threaded bolts where water will be present as the droplets can travel up the thread and into the joint, thus weakening the fastened materials. With a partially threaded shaft you can leave just enough of the thread showing to allow the nut to be tightened, sealing the joint further by cutting off the excess thread.
A bolt is a long shaft that has threads cut into it. The most common type of bolt is an externally threaded fastener with a head at one end and some kind of nut as the matching part to be screwed onto it. There are probably bolts in any room you’re in right now!
The word ‘bolt’ comes from old French where it meant anything solid or firm – like we still use today when we talk about something being bolted on to a car, for example. Bolt originally came from the Old French term “boulte”, meaning “log.”
By 1340, people were using bolts to describe any large piece of metal used as weaponry such as swords and axes. Such is the strength of them that they now have their name as a strong connector between two (often heavy) materials.
What Are Bolt Standards?
Most types of bolts and fasteners are given a grade which shows the minimum acceptable standard of mechanical performance that the fasteners must meet. The higher the grade the higher the mechanical strengths of the bolt.
These standards of bolt characteristics are carried across all types when comparing measurements.
Types of Bolt Parameters Include:
- Size, in imperial or metric
- Threads per inch
- Material
- Finish
- Length
Types of Bolts
There are many to choose from, but these six types of bolts are the most common for fixing.
Ankerbolts/Anchor Bolts
These bolts are usually used to connect structural and non-structural parts to concrete. Wooden and steel beams are often mounted onto concrete walls and floors using Ankerbolts. Sometimes called Thunderbolts, they screw into pre-drilled holes and can be even further tightened using a washer, which acts as a grip.
Carriage Bolts
Carriage bolts can be used to tighten wood to metal, as its square undercut beds into the wood when tightening, giving a more stable and stronger fit, especially when tightening the nut. Sometimes known as coach bolts, they are often seen as a simple self-locking bolt. They are mostly fully threaded, except in some circumstances on the longer sizes. Most M6 coach bolts are fully threaded as they do not come in long enough sizes that require a thicker shaft. It’s important to note that there is a big difference between coach bolts and coach screws.
Hexagon Bolts
Hexagon bolts are designed for strength and are widely used in engineering projects for this reason. They have a partially threaded shaft, with the thread usually running three times the diameter of the shaft. Unlike carriage bolts, the head of the hex bolt will spin when tightening with a nut, so you will need to hold it in place with an extra wrench or socket.
Hexagon Set Screws
Hexagon set screws are similar to coach bolts, however, they have a hexagon head and do not have the square undercut found on a coach bolt. These bolts will also need holding with a wrench when tightening. They are available in metric and imperial sizes, stainless steel, zinc plated and brass. The threads can either be course of fine.
Flanged Bolts
These bolts are like the hex set screws and hex bolts, but the flange under the head acts like a built-in washer. This acts to spread the tension over a larger surface area, whilst exerting less pressure on the material below. They can also be known as frame bolts.
Roofing Bolts
These bolts are fully threaded but the head comes with a flat underside and a domed top side with a slot for tightening. With the larger head spreading the tension, they are ideal for thin woods and soft materials.