Screwdrivers and drive bits are crucial elements in mechanical couplings and provide the link between the machine or the hand and the screw. Choosing the right equipment for the right application has a huge impact on the result of the work. Here Wera Werkzeuge GmbH explains the different types available.
The five most common drive profiles are slotted, Phillips, Pozidriv, TORX® and hexagon.
Slotted drives feature a simple slot as a host for the blade, however, they have a disadvantage of a lack of centring – making it easy for the tool to slip out of the screw. The screwdriver tip ‘Lasertip’ from Wera literally bites into the screw without damaging it, taking away this disadvantage.
The second common drive profile is the Phillips defined by two rectangular slot cross sections. Compared to the classical form of the slot version, because of the four corners of the Phillips profile the interaction with the screw is quite easy. But, even in this profile the user has to counteract the cam out forces. Once again, the Lasertip screwdriver can be used here. The Phillips profile is very often confused with the Pozidriv profile, which in erroneous use leads to damage of tool and screw.
The Pozidriv profile is the third common drive profile and is a further development of the cross head profile. Two additional crosses supply an additional stabilisation during the screwdriving process. Although this is an improvement, the Pozidriv profile still fights with the problems of slipping.
Another common profile is TORX® – a star shaped wave profile with six rounded cams. When compared to traditional screw profiles, more torque is transferred without damage to the screwdriver and screw when using TORX. This life extension of the screwdriver and screw results from the low radial forces. These are given by the absence of edges and the parallel form of the six profile elements.
Finally, the hexagon is one of the best known and most widely used profiles and for sockets there is no alternative. For the power transmission, this is a relatively unfavourable constellation, since the stress concentration is very high and can result in deformation of the screw. The Wera Hex-Plus provides larger contact zones in the screw head, which reduces the notching effect to a minimum and protects the profile.
Special bit categories
As with profiles, there are common bits used in the fastener industry – impaktor, stainless and BiTorsion bits. Impaktor bits are ideal for use with power tools giving high and intense high torque. It is important the bit does not break, so the solution is the maximum utilisation of the material properties. These bits are designed with a special geometry to meet the extreme demands. The special manufacturing process provides an above average service life.
Also available are stainless bits from Wera, which are ideal when working on a stainless steel surface where the smallest piece of rust can jump over to the stainless surface.
Finally, BiTorsion bits have a softer BiTorsion zone, which Wera points out reduces the hardness of the shaft by about 20% in comparison to the drive tip. This means that the peak loads that cause bit breakage and premature wear are absorbed in this zone – enhancing the service life of the bits significantly.
Special screwdriver categories
Which kind of screwdriver is chosen depends on the work to be done. If the screwdriver is sometimes also used for chiselling, a chiseldriver with ‘pound thru’ blade for heavy-duty should be used. For work on small scale screws, Wera’s Micro screwdriver is recommended. When working under tension a VDE screwdriver (recognisable through the colours red and yellow) should be used.
Screwdrivers can often cause calluses, so it is important to ensure that an ergonomic handle, such as the one on Wera’s Kraftform Plus, is used for normal applications. The handle is modelled by the shape ofthe human hand to ensure maximum user comfort.
Having joined the magazine in 2012, Claire developed her knowledge of the industry through the numerous company visits, exhibitions and conferences she attended both in the UK and abroad.
Claire prides herself on keeping readers well informed and up to date with the latest industry news.