Screw drive types are one of the oldest standards contests in woodworking. The two most popular drives for general-purpose wood screws are currently the traditional Phillips drive and the more recent Torx or star drive.
While many other drive types are still holding their position, the Phillips and the Torx are clearly the leaders: estimating by the number of screw models with a given head listed at hardware retailers, these two types together cover around 70% of the total wood screw market.
But which one is better for your application? And why are there still two?
In this article, I will compare the pros and cons of the Torx and the Phillips as wood screw drives based on my experience. If you are planning a project involving screw connections, I hope this review may help you in deciding which drive type to go for.
So how do the Phillips and Torx drives compare? A short version of the answer is: The Torx allows higher torque transmission and better screwing ergonomics, but should preferably be used with a torque-limiting clutch to prevent overdriving or overloading the bit and the screw. The Phillips, on the other hand, is protected from destructive overload by cam-out and has higher availability and sometimes lower price, but more limited torque capacity and worse ergonomics. Neither drive is simply superior to the other, and the choice between them will depend on the application and your personal working style.
We will next break down the comparison to six categories: torque transmission, centering, overload behavior, ergonomics, availability and price.
|Category \ Head:||Phillips||Torx|
|overload behavior||cam-out||bit/screw fail|
1 Torque transmission
The Torx and Phillips drives differ in torque transmission capability. Transmitting the rotating motion and torque from the driver to the screw is the main job of the screw drive; a good screw drive is one that allows you to transmit a sufficent torque into the screw head easily and efficiently.
By virtue of its shape, a Torx drive is very efficient in transmitting torque: it is a shape-locking form with high contact angles and no axial forces generated. For a given torque level, a Torx drive actually generates the lowest contact pressures between the bit and the drive socket of all the common drive types. You can find a similar interlocking lobular or star shape also in the drive shafts of many vehicles, where torque transmission efficiency has long been a central concern.
The Phillips drive, by comparison, is only moderately efficient in torque transmission. First, while the Phillips is also shape-locking, the conicality of the sides of the cruciform head lead to an axial force which tries to push the bit out of the socket; as anyone who has used the head knows, it tries to “cam out”. Second, the lobes in the bit are actually relatively thin and weak, and could transmit much less torque than a Torx drive of the same diameter before splintering. Most of the time, this second weakness is masked by the first, though: a Phillips bit usually cams out before you have time to load it to fracture.
Conclusion: In torque transmission, Torx is the clear winner.
Centering means the capability of the screw drive to maintain the bit and the socket correctly aligned without active aiming on the part of the user, and is essential both in automated and manual screwing.
Fortunately, Phillips and Torx drives both center well and do not usually wander off contact. Both continue to function even when the bit and the screw socket are at a moderate angle, which may happen accidentally during the driving, or be forced by lack of space around the screw.
That said, the Phillips does have a slight advantage over the Torx in centering. Thanks to the conicality, the Phillips is able to center perfectly also if the bit is worn, the socket is worn, or you are using the wrong bit size altogether!
Conclusion: both drives center well, but Phillips has an minor advantage.
3 Overload behavior
When you apply more torque to a screw than its drive is designed for, you are overloading the drive, which may easily happen with a stuck screw, for example.
The Torx and Phillips have quite different overload behavior. As already alluded to above, a Phillips drive will typically cam out before either the bit or the screw breaks. As a cam-out is not very serious event, this can be considered a useful safety feature in the Phillips drive.
However, the cam-out feature of the Phillips also has its flip side. First, it may limit the maximum transmissible torque also when it would be actually needed, like in removing a old screw stuck in place. Second, it creates the need for you to steadily push the driver even during normal operation. Third, a failure to push hard enough will lead to cam-out and bit or screw head wear well before any critical torque level has been reached.
A Torx bit is very efficient in transmitting torque and will not usually cam out, even when overloaded. While this reliability has its benefits, it also means that overloading a Torx bit will lead into failure of either the bit or the screw shank. Sometimes it is the screw that snaps, sometimes the bit; both are less than desirable events. You can avoid the risk by either being very careful or by using the driver clutch to limit the maximum torque beforehand.
Conclusion: Which overload behaviour is better, is somewhat of a matter of opinion – there is no clear winner here.
The choice of Torx vs. Phillips may have a substantial impact on screw driving ergonomics. Although screws are these days mostly driven with a cordless driver, which has relieved the operators from the tedium of manual driving, it is still up to the operator to hold both the screw and the driver steady during the driving.
Driving a Torx screw is as easy as it gets: the operator just has to hold the driver lightly in contact with the screw head, and the bit and socket will take care of the rest.
A Phillips screw, by contrast, requires a more substantial effort: during all of the driving, you have to push the driver axially against the screw to avoid cam-out. This presents and extra strain on the operators hand, which may become a serious issue, particularly when large numbers of screws must be driven overhead or in other difficult positions.
Conclusion: In ergonomics, Torx is the clear winner.
The choice between Torx and Phillips may also be influenced by availability of the appropriate screw with the drive you want.
The Phillips is the more common type by a wide margin: at the moment of writing, wood screw items at Lowe’s, for example, outnumber Torx (or “star”, “lobular”) by 771 to 383 items – with Phillips, you have double the selection to choose from.
The Torx seems to be slowly gaining in popularity, however, so the situation may well change some time in the future. Considering that the star-shaped head has already taken 50 years to get to this point, I would not expect a total change of seas during this decade.
Conclusion: the Phillips has higher availability, and wins this comparison.
Phillips and Torx drive screws sometimes differ in price, which may affect your choice between the drive types.
On average, screws with a Phillips head seem to be more affordable than Torx drive ones. A part of this difference may be due to genuine manufacturing concerns, such as a Phillips drive being actually easier to punch into a screw blank than a Torx drive.
However, I was unable to find a consistent price premium for the Torx in a quick head-to-head comparison of screw models that are otherwise the same, but come with a different drive. Rather, it seems that Torx drive screws are available mainly from premium or name brand manufacturers, while low-cost unbranded screws are mostly Phillips. Further, on average, Torx drives appear to be more popular in large screws and in screws for demanding applications than in small or general-purpose screws. So, although Torx screws appear to be more expensive, this seems to be down to other properties than the drive.
Conclusion: In terms of price, Phillips has a lead, but mainly through availability of low-cost options.
Technically, the Torx is superior to the Phillips in the main task of a screw drive: transmitting torque. However, as we saw, this is not the only evaluation criterion for a screw drive: overload behavior, price and availability play a part too. The higher maximum torque capacity of a Torx drive may itself also become a serious disadvantage, if it leads you to drive the screw head through the board or snap the screw or the bit.
The merits of the Phillips and Torx drives are to a large extend down to application, working style and personal preference. Here, I list my recommendations for different applications or emphases:
Max torque: Torx
If you are like me and want to be sure you can get the maximum torque into the screw when needed, and see no trouble in limiting the torque with the clutch at other times, you probably want to go with the Torx. This drive will give you all the torque you need with little effort on your part, which is particularly important when you are driving large screws.
Best ergonomics: Torx
If you know you will be screwing a lot in difficult positions – overhead, reaching out with one hand, or in tight spaces – you will want to go with the Torx drive: it takes the extra strain of pushing the screw from your hands.
Safer overloading: Phillips
If, on the other hand, you do not like to adjust the clutch in your driver, you should go with the Phillips drive: it will in many cases help you avoid overdriving or overloading the screw.
Cost-efficiency in easy applications: Phillips
If you do not mind providing the steady axial push needed by the drive or are building a deck and driving the screw downwards in a good position, using a Phillips screw is just as easy as using a Torx. In such applications, you could take advantage of the low-cost Phillips options and save some money.