When you look at the fasteners on your pride-and-joy, you might wonder why a particular type was chosen. Back in the early days of Japanese motorcycles, we wondered why there were so many easily rounded-off Phillips screws. Today the standard fastener is a nut or bolt with six flats, though Phillips, Torx and Allen heads are equally common.
You want reliable fasteners that are easy to use. The manufacturer wants fasteners that are affordable in bulk and work well on the production line. Allen heads are common for a number of reasons: The outer circumference is round, so they aren’t prone to catching on boots or riding gear. Any tool marks are internal, so the fancy finish on the outside of your custom streetbike’s fasteners won’t get marred. Allens lend themselves to settings that leave the head of the fastener flush for a clean look. An Allen head also allows strong tool engagement, so will handle more torque than a screw. Finally, with a ball-end Allen wrench you can safely work where the tool is angled to the fastener. You can’t really do that with other fastener types.
The least-expensive Allen sets are simple L-shaped items. Generally, the entire shaft has the same cross-section, so if the end gets rounded-off, you can simply grind it shorter. Better-equipped toolboxes will have standard and extended Allen sockets and T-handles. Ball ends for the extended sockets and the T-handles are a bonus. Be aware that smaller ball-ends can easily twist their tops off, so use these where torque is limited and buy only high-quality tools with a lifetime warranty.