The Wright Spline™ is the highest strength wrench for high strength fasteners and is good for ordinary hex and 12 pt. fasteners too.

WHAT IS WRIGHT SPLINE™? Wright Spline™ is unconventional because it takes advantage of two things that have not previously been considered in wrench design. First, most wrenching problems occur in removing fasteners because the removal torque is frequently twice or more the installation torque. The second point is that most fastener heads are made on the small side resulting in substantial play between wrench and fastener. Wright Spline™ is better designed to deal with this clearance.

WHY IS WRIGHT SPLINE™ PREFERRED? A hex fastener produces large, non-productive radial forces, which tend to split the wrench or damage the wrenching surfaces of the fastener or wrench. The spline does not have these forces and, therefore, a spline wrench on a spline fastener will be much stronger than a hex wrench of the same diameter on a hex fastener. Wright Spline™ is an advanced spline design.

HOW DOES WRIGHT SPLINE™ WORK? Fasteners have gone from 60,000 psi tensile strength to over 180,000 psi, a 3:1 range. In addition, the use of the small 12-pt. fastener heads requires smaller wrenches to have twice their customary strength required to turn 6-pt. fasteners. Highest strength wrench for high strength spline fasteners and for ordinary hex and 12-pt. too! This results in a six-fold increase in required strength. Traditional 12-point wrenches were designed for single hex fasteners long before 12-point fasteners were in use. Although quality wrenches have been much improved in design and manufacture, they cannot cope with a six-fold increase. It is necessary to go to a new and unconventional profile-Wright Spline™.

WHY USE A WRIGHT SPLINE™ ON A HEX NUT? The Wright Spline™ was created to have the same diameter as standard wrenches. It transmits about the same amount of torque to hex and double hex fasteners as traditional wrenches. But, it has the advantage that contact is made far away from the corner; therefore, it does not depend on the existence of the corners and does not damage the corners further. It is for this reason that this wrench not only can turn all four styles of fastener heads, but also is the better design because it can turn the undersized and damaged fasteners better.

WHY USE A WRIGHT SPLINE™ ON TITANIUM AND OTHER LIGHT WEIGHT MATERIALS? These fasteners require less torque because they have less strength but they will still benefit from a high-strength spline wrench. The greater efficiency of the Wright Spline™ produces relatively lower forces, and the larger bearing area results in lower relative contact pressures.

WHY SPLINE WRENCHES AND FASTENERS? The combination of spline wrenches and spline fasteners can deliver twice the torque of 12-pt. wrenches on double hex fasteners and still more torque than hex wrenches on hex fasteners. This is done without any increase in the outside diameter of the wrench. This allows the use of higher strength bolts and, it allows these fasteners to be tightened to higher loads. Even more important, it allows these fasteners to be removed with less difficulty. Like many new ideas, they are being used first in aerospace, where weight and time savings justify their premium cost. Wright Tool has an improved design for fasteners which will lower the manufacturing costs and make splines more widely used. Also, splines are a good replacement for hollow head cap screws because they can work in the same space, and the new design is easier to clean than the hole of a socket head cap screw.

If a mechanic has a set of spline wrenches, he will find that they will turn single and double hex 12-point fasteners with corners that are too badly damaged to be turned with other wrenches. Also, they are superior for double hex fasteners. Some mechanics find that it pays to replace double hex headed fasteners with spline fasteners to make them easier to remove in the future.

Both diagrams below are for the same torque. But, the total force on the spline is only 40% of the total force on the hex tooth. The length of the red arrow represents the total amount and direction of force between wrench and fastener. With typical clearances, the fit is better and the contact area is 44% more.

Double Hex Wrench and 12-Pt. Fastener

Wright Spline Wrench and Fastener