Hex and Torx Keys

Hand tools for inhex and Torx profiles

The common slot in a screw head can transfer only relatively low torques. Another disadvantage of the straight slot is that it does not guide the screwdriver blade properly. In the search for an alternative to the screw head slot, attempts were made in the early years of the 20th century to provide the round screw head with an embossed hexagonal profile - the reversal of hexagonal screw head to socket wrench, so to speak. In 1910, a certain William G. Allen patented a specific manufacturing process for such screw heads. As Mr. Allen only patented the manufacturing process and not the idea of the inhex socket itself, it wasn't problem at all for other companies to produce similar screws. In 1936, the Wuppertal-based company Bauer & Schaurte patented the inhex socket screw itself for Germany under the name Inbus. As a result, we are still not allowed to write Inbus screw today, although most German-speaking people say Inbus when they mean hexagon socket. However, a inhex socket - regardless of whether according to Allen or Inbus - transmits around 10 times the torque of a Phillips screwdriver with the same screw shaft diameter.

And Torx?

Transmits even more torque and guides the tool even better. Simply changing the profile from a hexagon to six teeth with curved flanks (like a small chain sprocket) increases the transmittable force many times over. This is an immense advantage, especially in the automated assembly of screws. Harley-Davidson itself also quickly recognized the advantage of the Torx profile for highly stressed screws such as those for brake discs and has switched to it. With Torx on the market worn-out countersunk socket head screws are a thing of the past.

Ball heads

The basic layout of socket and Torx screw heads relies on the screwdriver positioning the tool exactly in the center axis of the screw. However, if the tip of the tool is turned off in a rather spherical shape, this tool can transfer axis angles of up to 25°. This is just right if, for example, a flange protrudes above the screw head and there is just enough space to insert the screw into the thread, but the tool can no longer be positioned straight. Ball heads are available for inhex socket and Torx profiles.

Socket bits or screwdriver-like handles?

Torx and hexagon socket tools are available in three standard shapes: with a screwdriver handle, as a socket or interchangeable bit and in an L-shape with a short and long shank. The screwdriver handle is comfortably gripped by the hand, but transmits less force than the socket bit, where the force transmission depends rather on the handle ("ratchet"). The L-shaped wrench offers both: power transmission via the long shank and use as a screwdriver. The short end acts like half a T-handle.