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For years PVCu windows and doors were either reinforced with steel or not reinforced at all. That meant there was a clear ‘one or the other’ choice when it came to deciding which fasteners to use during manufacturing. Not so today, however.

Steel reinforced PVCu frames would require a screw with a drill point, whereas unreinforced frames wouldn’t. In the pursuit of greater thermal performance to improve the energy efficiency of our homes and buildings, however, new thermally enhanced reinforcements have come into play – and these are set to be used more and more in future.

Adding new materials into the frame construction means we need to think differently about the screws used for structural purposes and those used to attach hardware elements such as friction stays, keeps and door hinges. Getting it wrong will not only impact on production efficiency and safety, but it will also compromise the quality of your finished products.

But there is also the issue of the many different types of steel reinforcement that is designed to fit specific profile systems. These may be U-shaped sections or box sections and they could even incorporate a folding of the steel or a  V-groove. These variations could affect how securely you are able to make the attachment.

The rise and rise of thermal inserts

Thermal inserts are becoming increasingly popular for good reason. They have a strength to match steel but the benefit of a much lower thermal conductivity. This makes achieving a lower whole window or door U-value easier, keeping the industry on track to comply with the lowering of maximum U-values permitted every time Part L is reviewed. Hence why systems such as Profile 22, Duraflex and Eurocell are all now available with thermally enhanced reinforcement instead of steel.

Profile 22 Optima window profile featuring an RCM insert.

And there are addition benefits beyond thermal improvements. The Epwin Group’s RCM (recycled composite material) reinforcement, launched back in 2007, has the advantage of being manufactured from post-consumer waste plastic. This is a win-win from an environmental perspective, helping to cut energy use in customers’ homes and reducing the amount of plastic waste going to landfill.

From a window and door manufacturing perspective, where a frame is reinforced with a composite material, fasteners with a drill point cannot be used. The drill point is designed to create a hole in steel for the narrower thread to engage – drill into a composite material and the fastener thread will not be able to engage.

The good news is that there are excellent options available in the Rapierstar range. For example, with Eurocell profiles, you would typically attach a lock keep to a reinforced frame using CSR 3.9 x 25 – a 25mm countersunk screw with a drill-point. But when the steel reinforcement is switched to thermal inserts, all you would need to do is use a CFG 4.3 x 25 instead. This has a fast starting gimlet point that is perfect for insertion into composite materials and a deep thread form for a strong grip and, hence, good pull-out strength.

Getting the right results with steel reinforcement

A fastener with a drill point will always be needed to drill into steel – a screw such as the CFG simply will not be able to create a hole and, if you try to use one, it will end up slipping or snapping can risk injury.

But using a drill point fastener might not be the only thing you need think about when assembling windows and doors featuring steel reinforcement. The design of the reinforcement itself could also hinder the quality of the attachment.

This is something we cover in detail in the Info Point section of our website because it can cause headaches for fabricators.

For example, your profile may feature a U-section reinforcement that is unsupported at one end (i.e. the open part of the U-shape) which just happens to be where you are trying to attach hardware with a drill point screw. Here, as you push down, the drill point is not able to engage and instead simply ends up bending the reinforcement.

The solution here is not to use a different type of screw – you need to use different reinforcement. In this case a box section where the steel will stay at 90 degrees when you insert the screw.

How technical collaboration is delivering better quality windows and doors

A PVC-U door hinge being tested for the strength of its attachment to an outer frame.

What is the result of following this kind of best practice? To give the industry some supporting evidence about how the choice of fasteners makes a difference to the quality and performance of finished windows and doors, we recently teamed up with leading hinge manufacturer SFS to put our ideas to the test.

The testing looked at the impact of switching the type of fasteners used to attach a Dynamic hinge to PVCu outerframes from various different profile manufacturers. The results showed that the change could deliver improved pull-out strength (i.e. the strength of the attachment between the frame and hinge) by as much as 56%!

You can read more in the article published about the testing in Glass & Glazing Products magazine here. While this testing was not looking specifically at the role of reinforcement, it is important and relevant as it shows what a difference the fastener choice can make.

Access technical support from Rapierstar

Rapierstar is the largest specialist supplier of fasteners to the UK and Ireland’s window and door industry, which means we have a wealth of expertise and experience to assist fabricator make the right choices.

If you have any questions about which fasteners to use in any aspect of window or door manufacturing, simply send us a message via our Contact Us page or give us a call.

This email address is being protected from spambots. You need JavaScript enabled to view it. Technical & Marketing Manager at Rapierstar 


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