Torx and Torx Plus are trademark designs of a standardized screw drive.
The difference between a Torx and Torx Plus is in the shape of their head profiles. Torx has a six-point star-shaped design, whereas Torx Plus is a modified design of Torx with elliptical-based geometry. Thus, Torx Plus maximizes tool engagement, thereby facilitating higher torque transmission.
This article discusses the difference between Torx and Torx Plus profiles, followed by a brief description of the Tamper-resistant Torx Plus drive and Polydrive.
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Difference Between Torx and Torx Plus
The following table highlights the difference between a Torx and Torx Plus screws
|Socket Geometry||Six-pointed star-shaped socket||Elliptically based geometry|
|Drive angle||15 degrees (reduces tool life)||Zero degree|
|Sidewalls||Less engagement||Maximum engagement|
|Size||Universal, identified with T before the number||Universal, identified with the letter "T" and "P" before the number|
|Tolerances||Wide tolerance provides a loose fit||Clearance fit|
|Torque Transfer||Higher and secured torque transfer||Improved and optimal torque transfer|
|Load||Little end load||Little or no end load|
|Tool bit life||Better Tool Life||Extended tool life|
|Compatibility||Not compatible with Torx plus drive||Compatible with Torx Drive|
Difference in Socket Geometry: Torx vs Torx Plus
The primary difference you can easily observe when seeing Torx and Torx Plus screws is their geometry.
A Torx screw is a six-point star-shaped screw fastener popularly known as star-headed or Hexalobular.
In contrast, a Torx Plus screw has elliptical-based geometry. In addition, the pointed ends of a Torx screw are modified to flat ends.
This modification in design facilitates more area of contact between the tool and the recess in the screw head.
Drive Angle Difference
Drive angle describes the driver's profile or the recess in the fastener.
The drive angle for a Torx fastener is 15 degrees, whereas for Torx Plus, it is 0 degrees.
This helps Torx Plus eliminate the radial stress present at the point of contact between the driver and the recess in the screw head.
The drive angle in Torx makes it unsuitable for high-speed assemblies.
The vertical surface of the recess (profile) is known as the sidewall.
Torx's flat sidewalls offer more driver engagement than the sharp corners of the Torx, thereby minimizing tool slippage and avoiding the formation of concentrated stress points.
The sizes of Torx and Torx Plus are universal, whether an inch or metric standard.
Sizes of Torx fasteners are specified by the letter "T," followed by a number indicating the head size.
Whereas the sizes of Torx Plus fasteners are specified by the letter "T" or "I" along with "P." This letter is followed by a number denoting the head size.
The wider tolerance range of the Torx results in a loose fit between the driver and the fastener. Toex Plus doesn't have this issue.
The border of the contact surface provides a good clearance fit between the tool head and the fastener, enabling faster assembly and increased productivity.
Torque Transfer Difference
The six lobes of the Torx design offer a higher and secured torque transfer.
Because of the larger area of lobes present in Torx Plus, it increases the torsional strength, thereby offering higher torque transmission than Torx.
The ease of driving the screw enables a more significant torque transfer even at high speeds.
Cam out Risk
Cam out occurs when the tool bit slides out of the fastener head while turning. This happens when the torque required to turn the fastener exceeds a specific limit.
Further, it leads to the wear of either the tool bit or the head of the fastener.
The wide vertical surface of the Torx Plus eliminates the chances of cam out, thereby securing the tool bit within the recess and preventing any damage to the tool bit or the fastener.
Load, also known as end load, indicates the additional pressure needed to keep the tool engaged within the recess.
Torx systems require about 8% additional end load for a smooth operation. This can lead to lower productivity and fatigue in the workforce.
Comparatively, Torx Plus requires little or no end load to keep the driver engaged.
Tool bit life Comparison
The star-shaped and elliptical-based geometry of Torx and Torx Plus screws offer maximum tool engagement, improving the tool life and maximizing torque transfer.
The improved design of Torx Plus provides extended tool life than the Torx.
The profile of Torx Plus is an improved version of Torx. It involves flattening the pointed edges of the star profile, i.e., of the Torx.
You can use standard Torx drivers to work on the Torx Plus screws, but you'll observe wobbling during the tool engagement because of a loose fit.
In contrast, Torx Plus standard drivers are incompatible with the Torx screws due to the mismatch in the profile design.
What's a Tamper Resistant Torx Plus drive? How's it different?
A tamper-resistant Torx Plus drive is also known as Security Torx or Pin-in-Torx.
Its unique design prevents unauthorized personnel from hampering the joint.
The tamper-resistant Torx Plus screw head design includes a solid security pin at the center of the five-point or pentalobular design.
Whereas in a tamper-resistant Torx Plus drive, it has a slot at the center of its head to accommodate the solid security pin.
The pentalobe ends offer reduced cam out and thus provide an exact fit and faster assembling.
The sizes of these tamper-resistant screws or drives are indicated by the letter "TR" followed by the head size number.
Its unique design (non-symmetrical elliptical-based geometry) offers a broader contact area and tight tolerances, providing an optimal torque transmission.
These types of screws are commonly used in high-security applications like the electronics and automobile industries.
How Polydrive Compares to Torx and Torx Plus
The following table compares Polydrive with Torx and Torx Plus
|Geometry||Splined shaped||Six-point star-shaped||Elliptical based|
|Application||Drive Shafts, brakes||Hard disk drives||Consumer electronics|
The geometry of poly drive is different from Torx and Torx Plus.
Though Polydrive looks similar to Torx Plus, there is a subtle difference.
The profile of a poly drive is a splined-shaped six-tooth recess, whereas a Torx Plus is elliptical-shaped.
Because of the specialized design of Polydrive, it has more contact with the drive, offering the highest torque transmission amongst all other profiles of screw recess.
The capability of transmitting the highest torque makes it an ideal choice to be used in parts of power transmission, for example, brakes and drive shafts.
Final Thoughts - Best in Performance?
Though standard Torx tools provide a loose tool engagement, you can use them to turn the Torx Plus screw.
But you can't use a Torx Plus drive to turn Torx screws.
The Torx Plus screws help improve the production rate by increasing the assemblage performance.
The ability to transmit higher torques makes loosening corrosion-tightened screws easy.
Frequently Asked Questions
How to maintain Torx drivers?
To maintain Torx drives, you must preserve the driver tips, which are vital for a longer tool life. Keeping the tool profile clean and sharp is recommended to achieve a good grip. Do not use the driver tip as a punch or as a wedge.
Can we use an Allen key to tighten a Torx screw?
An Allen key can tighten a Torx screw, but it is best not to do so as it offers poor tool bit engagement. However, in case of emergencies, Allen keys do come in handy.
How to determine the size of a Torx screw?
The distance measured from a star point to its directly opposite end helps in identifying the size of the Torx screws. We can determine the commercially available size using the measured value and referring to a standard chart.