Can Phillips top what has become the most famous screw thread in the world?

Written by: Justin Cunningham | Published:

It is the most famous screw thread in the world. The Phillips screw drive – that's the system used to turn a screw – is known by just about everyone. Indeed, when asking for a screwdriver the follow up question by the layman is usually "Phillips or the other one?"

Since its introduction, of course, there have been many hundreds of weird and wonderful drive systems developed that offer numerous advantages. The originator of the Phillips drive system – The Phillips Screw Company – continues to operate throughout every sector of industry and is still innovating fastening and joining technology.

The Phillips Screw Company has brought to market a number of unique alternatives in recent years that aim to improve upon the traditional drive system. These have been aimed primarily at the aerospace industry, which always strives to save weight where it can.

The limiting factor with many fasteners – including those with the classic Phillips drive system – is the amount of torque that can be put through it. A greater torque requirement has traditionally meant either that larger fasteners have had to be used, or more of them. Either way, significant weight is added to a joint.

Calculating the necessary strength of a joint is fundamental to selecting fasteners and is the starting point for determining appropriate fastener diameter, head style and size, and the type of material to be used.

This led Phillips to develop the ACR Torq-Set Drive System. This is an offset cruciform drive system that allows more torque to be applied. Along with the flat walls being able to transmit more torque into the fastener, the driver will also not 'cam-out'; an inherent feature of the original Phillips drive system.

The Torq-Set is used extensively by the aerospace industry. The weight saving possible by using fewer and smaller fasteners can be significant when looking at the entire assembly of an aircraft. And, with the drive for lightweighting perhaps more prevalent than ever, Phillips has developed another drive system to offer even more improvement.

The innovative Mortorq fastener uses four curved wings to 'provide full contact of the driver over the recess wings' that results in an unmatched ability to transmit torque into a fastener with more contact area on the drive wall.

"The Mortorq is helping the aerospace industry reduce the weight of its aircraft by allowing the use of much shallower heads on the fasteners," says Michael Mowins, president of global licensing at the Phillips Screw Company. "These are able to apply the same amount of torque, and it's that ability which is the major factor when sizing fasteners. You can see the innovative shape and this allows for a longer core to be used and ultimately results in a high-strength bolted joint that weighs less."

The design of the Mortorq also minimises the possibility of damaging the fastener, tool, or surrounding area. If the fastener drive head is damaged during tightening, the wing-like layout usually permits the fastener to be easily removed.

The rounding of conventional Phillips fasteners can frustrate at best and, if it stops the fastener getting tightened properly, can lead to failure. Its removal wall also means that it is capable of extremely high removal torque without cam-out to allow bolts – even if they are painted, thread locked or rusted in place – to be removed.

As the Mortorq is able to transfer torque so efficiently, it has meant that Phillips has been able to make the head-to-shank part of the fastener smaller. This can remove even more weight if used throughout an assembly. Compared to the spiral drive system the Mortorq has 12% less head volume, 4.4 times more surface contact and the removal wall has 7.1 times more surface contact on the removal wall.

And improvements over the popular Torx head – known for its star-like hexalobular design – are equally impressive, with the Mortorq having 13% less head volume, 8.6 times more bit contact of the drive surface, and 13.8 times more bit surface contact on the removal wall. Taking the same head diameter as the standard Torx and Torq-Set drive head, the Mortorq can apply almost three times the torque per square inch.

This weight reduction capability has been used by Boeing on its 787 Dreamliner, Northrop Grumman on the B-2 Bomber and Rolls-Royce on its Trent 1000 and XWB engines. As you might expect, these fasteners are made from aerospace-grade alloys.

However, for more mainstream applications with the same need for less weight, Phillips has produced the Mortorq Super. It uses the same spiral wing drive layout which permits exceptionally shallow recesses to be used.

The Mortorq Super is a stainless steel version of the aerospace grade fastener that offers many of the same advantages of high-torque capability that enables lighter weight assemblies, while taking up less space. This is particularly advantageous in tightly packed subassemblies often seen in compact electronic devices.

The drive system mainly seeks to replace standard hex socket drives and also the hexalobular socket style drive having almost 50% less head weight and over 50% less head volume in comparison. Its minimal head height also reduces the weight of fastened components, and permits strong and secure joints with less material and lower weight.

Ultimately these innovations have come at a time where there is intense interest and development around joining technologies. As multiple materials are increasingly used in single products, new joining methods are increasingly being sought.

Bonded tapes, adhesives, and snap-fit assemblies are becoming increasingly popular in many industries. However, it seems fastening companies are keen to keep bringing new ideas to the fore that offer improvement and advantage to users.

Phillips – the secret to success
Born in Oregon in the US, Henry F. Phillips purchased the rights to a socket screw and redesigned the screw with a cruciform recess. The significance of the 'crosshead' or Phillips screw lies in its self-centring property.

Unlike a traditional slot screw, which requires a person to simultaneously centre the screw in its hole, steady the screwdriver in the slot and then use the screwdriver to turn the screw, the Phillips screw's cruciform head sits firmly on the screwdriver with no need to centre it.

The Phillips Screw Company is still a big part of industry 70 years on from when it was first granted a patent for its screw drive system back in 1933. In the years that followed, the Phillips drive system took off and was used throughout industry on everything from machinery to cars as it became apparent to engineers that mass production could benefit by the development of a self-centring screw that would work with power tools.

The original screw was devised to allow much easier and quicker engagement of a screwdriver with a screw over the existing traditional slotted screw. The alignment time may seem negligible but multiplied over thousands of times in a factory, the savings are palpable. Its other major selling point is the fasteners ability to 'cam-out' the screwdriver. This is its ability to roll out of the fastener once a certain torque is reached to prevent damage to the fastener.

There are many similar drive types such as the cross-recess screw drive (essentially two slots placed 90° apart) and The Frearson – also known as the Reed and Prince screw drive. Though very similar to the Phillips head, it has a more pointed 'V' shaped internal.

One advantage over the Phillips drive is that one driver or bit fits all screw sizes. The tool recess is also a perfect, sharp cross allowing for higher torque to be applied, unlike the rounded, tapered Phillips head, which was designed to 'cam-out' at high torque. It was developed by an English inventor named Frearson in the 19th century and produced from the late 1930s.

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