Flexible shaft nut drivers comparison
I bought the Wera 391 7mm for hose clamp use, and found it not actually very flexible. So I bought another two German/Europe made models to compare. I've only used the spring shaft type previously.
Wiha SoftFinish 372 (01438)
Stahlwille 12506 7
I wasn't able to source the Felo Ergonic 429 070 40 in my country. I like the handles, but the flexible portion of the shaft looks concerningly short. So no further comment about this one.
All the shafts are externally a ~9mm hard flexible plastic. There is no lack of nor noticeable difference in torsional rigidity in use. The Wera and Stahlwille have a fine coiled appearance and texture, suggesting a wire underneath. Deviation at the tip possible from straight ahead before significant resistance is encountered:
- Stahlwille - 87mm
- Wera - 69mm
- Wiha - 50mm
The stiffness within the movement range goes in the same order, with the Stahlwille being significantly easier to bend. This was at in house room temperature, but I don't believe it's the plastic giving the rigidity so this wouldn't matter. Interestingly, the Wera 393 S flexible bit driver has the same flexibility as the Stahlwille, despite having the same measurements as the Wera nut driver here. The lengths of the flexible portion of the shafts are Wera and Stahlwille 117mm, Wiha 98mm.
The outer diameter of the sockets is 11mm on all. The Wera's full internal depth of 10.8mm is hex shaped. The Wiha has 8mm of hex depth and a total depth of 14.5mm. The Stahlwille has 5.7mm and 14.5mm respectively. I can't see any of this making any difference in use.
The internal width of the sockets are Wera 7.06mm, Wiha 7.15mm, Stahlwille 7.04mm. Fit on fasteners wasn't noticeably different initially, but revisiting and comparing side by side after taking those measurements, the Wiha does have a little bit more play.
Usual comments about the handles. The Wiha and Stahlwille are similar sized and rubbery, the Wera is a little small (but perfectly adequate for this size of driver) and mostly hard. End markings on the Wera are very good, Wiha good, Stahlwille quite poor. They're all also marked on the socket, Wiha good, and the others fair. Varying anti-rollaway design, some of them probably work better.
Overall for my envisaged use and personal preference, the Stahlwille wins. If you don't need to maximise flexibility, I think you'd be happy with any of them. If you had a couple or a set stored together, you might want want the Wera or Wiha for the better markings.