Tool Tips
BY JOE HASS
HEX DRIVERS
“Click, click.” That is the unmistakable sound of a small hex wrench
slipping inside a setscrew, like those found on a knob of one of your
radios. The combination of wear and tolerances both on the setscrew and the hex driver can lead to the dreaded “click, click” sound
and to you scratching your head for a technique to remove the stuck
setscrew. The setscrew and hex driver should be manufactured to
tolerances of +0.000/-0.002. This tolerance is usually achieved
before heat-treating. Changes occurring during heat-treating can
change the tolerances, which can lead to a sloppy fit between the
hex driver and the setscrew and the dreaded “click, click” as the
driver turns inside the setscrew instead of removing it.
There is hope! Hex drivers are now available that have been
milled from drill rod to very tight tolerances with no additional heat-
treating. Further, the bottom of the driver is milled flat rather than
with a slight radius. That means that the driver is capable of catch-
ing the very bottom of the setscrew that probably has not seen any
wear or been damaged. They are available in both metric and U.S.
sizes, and they can solve the problem and avoid the “click, click.”
Another common problem is trying to reach a setscrew at an
angle. To solve this problem someone invented the ball driver that
has a small ball ground in the tip of a hex driver, allowing the hex
driver to approach the setscrew from an angle. A neat solution! A
firm called Bondhus has taken this feature a step further with the
ProHold line of hex drivers. On one hex face of each ProHold driver,
a small compressible plastic insert has been installed. This plastic
insert “holds” the setscrew onto the hex driver, even with the
92°- 15°
R0.06-0.02°
JIS Type-S
©1986
Japanese Standards
Association
O
E
Phillips
©1993
The American Society
of Mechanical Engineers
