A Quick Guide to Buying Channel Fixings
Whether you’re using Unistrut or another compatible brand of channel, you’ll need the right brackets and fixings to achieve the best quality job.
Unistrut fixings are specifically designed to work perfectly with Unistrut channel and brackets. Although as the market leader, most other brands and generic products are designed to conform to the same standards as Unistrut, and will offer a high level of corrosion resistance.
Below we look at the standard range of channel fixings and their functions, as well as a few more specialised equivalents.
Channel nuts are a simple and effective specialised nut for use with channel struts. They are designed with a rectangular shape which can be inserted between the channel edges and then turned 90° to fit against the inturned edges of the channel. Additionally, the nuts have a serrated groove which locks against the channel edges giving a secure locking fit. Plain nuts are ideal for the majority of applications, especially where cost is an issue, or where assembly can be done in advance, or access is easy.
In certain circumstances, for example when assembling channel at height, or where you need both hands for other things, you want a channel nut which will stay in place. Spring channel nuts are perfect for this as you don’t need to hold them whilst inserting the stud or bolt. Sometimes colloquially referred to as Zebs, in honour of the Magic Roundabout character Zebedee whom they resemble, these nuts are available with a long spring for 41mm x 41mm channel, or a short spring for the 21mm deep channel. The spring holds the nut in place leaving your hands free to hold other parts of the structure and tighten the bolt. It also ensures the nut won’t fall out which can save a lot of time when working up a ladder or on a platform.
As well as channel nuts you will use a lot of square plates when assembling channel support systems. They are a specialised washer which is 40mm x 40mm to fit neatly across the open channel struts. The stud is then tightened onto this, with a suitable hex nut and washer, into the channel nut behind providing a secure base for attaching other accessories.
- Choice of thicknesses
The standard thickness for square plates is 5mm, although thinner 3mm square plates such as Unistrut’s thin plate will suffice for the majority of applications. The thinner plates cost less, as they use less metal.
- Flat or lipped?
Square plates can be flat or have a lip which wraps around the edges of the channel which strengthens the structure by gripping the open edges. This can be particularly useful where there might be additional strain on the strut which might otherwise tend to force the edges apart.
- Choice of hole size
Square plates are available with a range of hole sizes corresponding to the thread sizes available in channel nuts. The threads range from M6 to M16 although M8 and M10 are the most common sizes in use. The larger thread obviously allows for a larger stud which provide greater strength to the connection of your fixing.
Hex bolts and nuts are combined with channel nuts and square plates to create a fixing from the channel length from which to secure building services.
Select a suitable hex bolt, or stud and hex nut, to lock down the plate and provide a connection for attaching other accessories. As already mentioned, the bolt / stud thread should correspond with the channel nut you are using.
For some channel assembly jobs, where speed is of the essence, it may be preferable to select a nut and plate assembly which uses a plastic spring that holds everything in place until you are ready to tighten the stud.
Although this type of nut assembly costs more than spring nuts it is the easiest to use, especially with slotted channel where the spring can sometimes get caught in the slots. As such, the time saved could more than offset the extra costs.
Rapid Rail is a small form-factor channel system which is designed to be quicker and easy to install than standard channel. Rapid Rail Hammerfix assemblies are among the fastest to install of any channel fixing. Insert and turn a quarter turn, the whole assembly stays in place, and then tighten the hex nut onto the stud.
Common Fixings for Securing Channel Lengths
Of course, in most cases channel support systems do not stand alone but are fixed to walls / ceilings using suitable anchors such as:
Two standard types of concrete anchors are wedge anchors and through bolt anchors. Both require a hole to be drilled of the correct size and depth to accommodate the wedge and bolt / stud. When the bolt is tightened it forces the anchor to expand in the hole creating the fixing. This type of anchor is cheap and effective although it does require some preparation and cannot be repositioned.
Concrete screws are specially designed self-tapping screws for driving directly into concrete. They merely require a starter hole, so they take less time to install and cause less dust and noise on site. They can also be repositioned and because there is no expansion, they can also be used closer together. The initial cost is greater but in many situations the time saved in installation may actually make them the lower cost option overall.
Channel sockets are commonly used when fixing channel to ceilings and walls to provide a firm fixing. Because channel lengths (struts) are 41mm wide and their open edges turn in on themselves, a channel socket rather than a regular hex socket is required. Channel sockets have a narrower wall than regular hex sockets and are designed to fit inside the channel section recess, to quickly drive both hex bolts and nuts.
Although a great deal of channel is used for purely practical applcations there may be aesthetic or health and safety reasons for using plastic end caps to produce a clean, smooth and stylish finish. Certainly, in any application where people may come into contact with the ends of any channel struts, these should be finished off with end caps.
For advice or further information on channel fixings, brackets and channel please contact our sales team on 01322 274226 or firstname.lastname@example.org