FALL 2021

10
THE DISTRIBUTOR’S LINK
Bruno Marbacher
Bruno Marbacher earned his mechanical engineering degree in Switzerland, he also holds a
business degree. He started out as a tool and die maker (poly-mechanic) and over the years he
has held various management positions in quality and engineering. During his time in America
he has developed and given numerous seminars on topics related to the proper use of mechanical
fasteners and machine elements, and assists engineers in solving fastening/assembly issues. His
has groomed and directed many young engineers in fastening/assembly technology. He now
offers his 40 years of experience through writing and lecturing.
DRIVING SYSTEMS FOR FASTENERS –
THE VERTICAL WALLED SYSTEMS
Dear Reader - in this article we cover vertical walled
drives, all kinds of socket drives. We listed the critical
functional features again; the details were described in
the first article (summer 2012 issue) we will cover the
most commonly used vertical wall drives.
Critical Drive Features
To choose a screw with certain drive there are several
things to be consider. The Critical Functional Features are:
¤ Amount torque it can absorb.
¤ Off-angle driver to drive.
¤ Ease off alignment/engagement
¤ Cam-out, tendency to push driver out.
¤ Durability of drive, repeated assembly
¤ Good Stick fit, hold driver in drive.
¤ The effect of the coatings on driver engagement
¤ Tamperproof, preventing unauthorized access.
¤ Its worldwide availability
Hex/Allen
Hex socket drive is
the first internal wrenching
hexagon. It was developed
by Standard Pressed
Steel Company (SPS) in
Philadelphia USA in 1911.
SPS gave it the tradename
“Unbrako”.
The German company Bauer & Schaurte patented
the hex socket in 1936 in Germany, and marketed the
products as “inbus”, commonly but incorrectly called
“imbus”. Inbus is derived from Innensechskant (Inner
6-edge)
TECHNICAL ARTICLE
In the USA the term “Allen key” is often used.
The hex socket screw drive has a hexagonal recess
and may be driven by a hex wrench, also known as an
Allen wrench, Allen key, hex key, or inbus as well as by
a hex screwdriver.
Feature & Concerns:
¤ Originally designed for machine tools so screws
could be recessed (for machine tools, heads should not
protrude to prevent injuries)
¤ Thick coating as well as zinc flake coatings may not
fill the socket at all or fill up, may over-bridge smaller
sockets, this is a concern for other socket products
for sizes M5 (#10) and up for socket set screws M8
(5/16) and up. Some coating applicators have special
centrifuges (special processes) that alleviate these
issues.
¤ The socket drive does not perform well in shallow
head designs (button heads, low heads etc.). sockets
may be reamed out (corner being rounded) making the
drive unusable
¤ Except for the shallow sockets they offer a great a
stick fit characteristic. On shallow socket a pilot hole on
the bottom of the drive can improve stick fit.
¤ This drive has a poor off-angle capability. Special keys
can improve that. This is essentially
true for all socket products. Very
commonly used worldwide for high
torque applications
¤ These drives are more likely
to be found on set screws and
machine screws than on wood
screws.
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