The cam-out force causes the blade to slip out of the screw head.
CamOut-Effect The CamOut effect is a common problem with conventional, conical profiles, such as the cross-recessed Phillips profile. In accordance with the triangle of forces, some of the energy cams out of the screw ("cam-out effect") causing the screwdriver or bit to slip out of the screw head. The user has to counteract this cam-out effect by an additional application of force.
Since the tool (e.g. slotted profile) tends to slip, this can cause injury to the user or damage to the surface of the work piece, for example the paintwork.A special surface coating on the tool tip (Wiha Dura, Wiha Diamond) can remarkably reduce the cam-out forces. This cam-out effect does not occur with profiles with straight side walls, such as Hex, TORX® or TORX PLUS®.
In comparison with the hex profile, the Torx has a much smaller range of tolerance.
Greater power, less effort With the hex design, the points of contact cause stress risers to develop. Damage to the screw head is almost inevitable and the transferable torques are relatively low in comparison with the level of force that has to be applied. Once again, the TORX® profile offers a much more positive torque/effort ratio. The maximum engagement between driver and screw head greatly facilitates force transmission.
Due to its shape, there are much higher stress concentrations in the hex profile.
Reduced stress concentration A danger when tightening and loosening screws is the high stress concentration that occurs when turning the screw. A high stress concentration occurs mainly in hex screw heads and this can cause stress in both the tool and the screw. The elliptically-based geometry of the TORX® profile and the associated lack of angular edges reduce stress concentration to a minimum. This protects and extends the tool life of both screw and tool. The elliptically-based geometry of the Torx profile also provides a very small range of tolerance between bit and screw. This results in a much better force closure. Regarding the TORX PLUS® profile the force closure was improved again through a working angle of almost 0° and the larger core diameter. This allows a higher torque transfer, prevents both screw and tool from damage and therefore extends again their tool life.