Know the Difference Between Philips and Robertson Screw? You Really Should
If you are more of a casual DIYer, you probably never give a second thought to the design of the screws you are using. But you might be amazed to find out that there are a massive variety of screw designs (and matching drivers) on the market.
You might be surprised to learn that screw you use can make a difference.
Here we'll discuss the histories, pros, and cons, of just two of these different types of screws — the Roberston screw and the more common Phillips screw.
Hold on tight, and you may find yourself paying much more attention next time your visit the hardware store.
What is the Robertson screw?
The Robertson screw, otherwise known as a square-drive screw or Scrulox screw drive, is, as the name suggests, a screw with a square-shaped socket in the head of the screw. The square-shaped socket and its matching square-shaped tool both also have a slight taper.
This feature makes the screw self-centering, thereby making it much easier to drive one-handed (very handy). They are also slip-resistant, unlike many other screw designs you are probably more familiar with in your daily life.
As the screwdriver is rotated, the interlocking square shape (and the taper) make it far less likely for the screwdriver to slip out of place. This is not only safer, but also greatly speeds up the process, as the screw and driver remain engaged.
When it was first introduced, the screw's design massively increased production speed and was less likely to damage products on which it was used. For this reason, it became a, more or less, instant success in many places that employed it.
As patents have expired for the screws, and more people have become aware of them over time, they have become a popular form of screw for woodworking and in general construction. Hybrid Roberston and Phillips head screws are also now very popular in the electrical trade — especially for devices like circuit breaker terminals and clamp connectors.
What is the history of the Robertson screw?
The Roberston screw was invented around 1908 by the Canadian inventor Peter Lymburner Roberston. Like many good innovations, the idea for the screw came from the inventor's frustration with existing products.
In this case, so the story goes, Robertson cut his hand using a slotted screwdriver, and decided enough was enough — there must be a better way to do things.
And so, the Roberston screw was born. Roberston would formally patent his design in 1910 but things didn't go too swimmingly for him at first.
The Steel Company of Canada did not take too kindly to his invention. Attempts were made to undermine his patent, but these later proved to be unsuccessful.
Another problem for Robertson was that a similar design had been patented in the latter part of the 19th century. However, that screw and driver had remained something of a curiosity, as manufacturing them proved too difficult at the time to make them commercially viable.
Despite this, Roberston's patent application was successful. The screws would go on to be a massive commercial success, as Robertson also devised a way to form the screws easily through a process known as cold forming. This is a metalworking process in which the metal can be shaped below its recrystallization temperature — normally at ambient temperature. Such a process normally takes the form of squeezing, bending, drawing, or shearing the metal into shape.
Today, cold forming is generally used to make large, flat sheets, complexly folded shapes, metal tubes, screws heads and threads, riveted joints, and many other metal objects. Another process known as rotary broaching is also very common for making screws today.
Soon after the patent was approved, Robertson formed Robertson Inc. to produce the screws and screwdrivers en masse. Amazingly, the company is still in business today, and its headquarters can be found in Milton, Ontario.
In fact, the screw (and its driver) are so popular in Canada that in 2007, the Canadian Broadcasting Company, in its show The Greatest Canadian Invention, placed the Robertson as #7 on its list of the 50 greatest Canadian inventions, directly behind #6, the artificial pacemaker, and #5, the Wonderbra.
Why don't Americans use Robertson screws?
For those readers in the U.S., the Roberston screw may still be an unknown quantity for you — despite its long and illustrious history in Canada.
The reason for this is actually quite interesting, and worth dwelling on for a moment.
The Roberston screw never really managed to break the American market for many decades after its first production. Nobody really knows why for sure, but one theory is that Henry Ford may have been a contributing factor.
Ford had tried the screws and found them to be particularly useful for the construction of his Model T cars. They quickly became key components for his assembly lines, as they saved valuable manufacturing time.
As a result, Robertson produced some special metal screws exclusively for Ford. Ford later attempting to create an exclusive licensing agreement with Roberston to produce the screws, but Roberston turned him down. This wasn't anything personal, just a consequence of Roberston not believing that an exclusive agreement would serve his company's long-term interests.
Without a guaranteed supply of the screws and drivers, Ford was forced to turn to the Phillips-head screw instead — thereby cementing its dominance in American industry for years to come.
Robertson, Inc. continues to produce a range of fastener products and drives for furniture makers, deck builders, sheet metal fabricators, etc. However, the original patent for the square-headed screw has since long expired.
For this reason, many knock-off versions have become ubiquitous. They are available in many major hardware stores and are easily sourced online.
When was the Phillips head screw invented?
In contrast to the Robertson screw, the Phillips screw is by far the more popular of the two. Invented by Henry Phillips in Portland, Oregon in the 1930s, this is the type of screw most people think of when they think about screws and screwdrivers.
Its cross-shaped tool indent, and matching screwdriver, are one of the most recognizable tools of all time.
The main reason for the development of this type of screw was to facilitate the use of power screwdrivers in industry. Phillips' design overcame several drawbacks to slotted screwdrivers, which was still the most common type of screw at the time.
As you probably know from experience, once the driver bit is inserted into the screw head recess, it will quickly seat itself as soon as the handle is turned. Very useful.
According to some sources, the Phillips screwdriver was purposefully designed to carn, or slip, out of the screw head to prevent overtightening and breaking of screws in assembly lines. This was important, as it was very hard to limit the torque in early power screwdrivers.
However, it is also important to note that this might be a case of revisionist history. For example, the original patent made no mention of this design feature, but is rather a result of the screw and driver's design.
While the sloped edges of the screw head and driver are great for self-centering, they do not prevent it from stripping when insufficient pressure is applied — as you are probably more than aware.
This is especially the case when slightly mismatched drivers are used to drive screws. For example, a type 2 Phillips screw should only really be driven using a matching type 2 Phillips driver. Another problem is that there can be many variations in cruciform screws that don't exactly match, like Posidriv, JIS, French Cross, etc type screwdrivers and screws. Any mismatch, even a subtle one, increases the chance of a cam-out.
Like the Roberston screw previously mentioned, the Phillips head screwdrivers are self-centering in the screw. They also keep a tight lock on the screw head, making it very unlikely that the screwdriver will slide out of the screw during tightening — unless overtightening occurs, of course.
What is the difference between a Robertson and a Phillips screw?
As you've probably already gathered, the main difference between the two screws is the design of their heads and associated drivers. There are also other differences between them, which give each some advantages and disadvantages over the other, depending on how they are used.
For example, Phillips screws tend to need more downward force applied to the screw, compared to a Robertson screw. This primarily prevents the driver from slipping off the screw.
This is especially the case for longer screws, like those used to attach cabinets to walls, etc.
With regards to the screws themselves, another main difference is the overall shape of the screw. The original patent for the Roberston screws shows it with a marked taper from tip to head. Phillips screws, on the other hand, are generally more elongated along their length. Modern examples of both are more or less similar, with the exception of the driver engagement recess in the head.
Another difference is the fact that the Roberston screw (and its driver) were specifically designed to be used one-handed. The main reason for this is that the screw and driver bind together very well, even if the driver's hand shakes. This obviously makes it much easier to use a Robertson screw compared to a Phillips screw.
It is important to note, however, that this advantage of the Roberston screw can also lead to the screw bits getting stuck inside the screw heads from time to time.
Another difference between the two is that it is generally easier to remove a painted-over Robertson screw than a Phillips one. This is primarily because the recess in the screw head of the Roberston screw is generally deeper, meaning even several layers of paint won't impede the engagement of the screw and driver by much.
Another difference between the two is the range of screw sizes generally available. Phillips screws tend to come in about seven main sizes, designated 000, 00, 0, 1, 2, 3, and 4 (increasing in size). Of these, sizes 0 to 4 are the ones you are probably most familiar with.
Roberston screws, on the other hand, tend to only come in five main sizes. Each size tends to be indicated by different colors to indicate increasing sizes — orange (#00), yellow (#0), green (#1), red (#2), and black (#3), with orange being the smallest, and black the largest.
Another important distinction is the compactness of the Robertson screw head. This allows it to work well as a trim head screw and other compact head screw uses. Phillips screws, however, do not generally lend themselves to such uses.
Is Robertson or Phillips screws better?
Bearing all that in mind, you may be wondering which, if any, is the better choice of the screw. It all comes down, ultimately, to personal opinion.
The ubiquitous nature of the Phillips screw makes it a lot easier to find the screws and drivers. So, if you are in a hurry to screw something together, you'll likely grab Phillips screws over Roberston ones.
However, this doesn't mean they are a better choice.
If you will be using a lot of screws over a short period of time, the Roberston screw is probably your better choice. As previously mentioned, this is mainly due to the lower tendency of these screws to cam out. This is not only frustrating but can cost you valuable time.
But, there is a third way, so to speak.
You will commonly find today a hybrid screw including both the features of the Roberston and the Phillips screw. These screws can be using either a matching driver of either design. A win, win.
And that screw enthusiast is all for today.
So, next time you find yourself in a hardware shop, take the time to consider picking up some Robertson screws rather than blindly grabbing a handful of Phillip's ones.
You may find you are pleasantly surprised by the outcome.