Torque-angle structural fastening system

Abstract

A fastening system that comprises a fastener and a single tool that provides both snugging torque and final tensioning to the fastener assembly, from a single side, with a single operator, with no torque feedback. The fastener comprises a nut and a bolt with a head and a shank extending axially from the head. The shank has at least one threaded portion and at least one splined portion, the splined portion defining the end of the bolt. The splined portion remains connected to the threaded portion after final tensioning. The tool comprises a first socket and a second socket, wherein the first socket is engaged with an outer surface of the nut and the second socket is engaged with the splined portion on the fastener. Snugging torque and final tension are both controlled by the tool.

1 . A fastening system comprising:
 a fastener comprising a bolt and a nut, the bolt having a head and a shank extending axially from the head, the shank having at least one threaded portion and at least one splined portion, the splined portion defining an end of the bolt, the threaded portion between the head and the splined portion, the nut having an inner surface and an outer surface, the inner surface in threaded engagement with at least one threaded portion of the bolt; and   a tool comprising a first socket and a second socket, wherein the first socket is engaged with the outer surface of the nut and the second socket is engaged with the splined portion of the fastener, wherein the tool provides both a desired snugging torque and a final tensioning to the fastener.   
     
     
         2 . The fastening system of  claim 1 , wherein the first socket rotates in a first direction and the second socket rotates in a second direction opposite the first direction. 
     
     
         3 . The fastening system of  claim 2 , wherein the first socket and the second socket rotate at the same rate. 
     
     
         4 . The fastening system of  claim 1 , wherein the tool uses turn-of-nut tensioning to provide the final tensioning to the fastener. 
     
     
         5 . The fastening system of  claim 5 , wherein the tool comprises an interface where a user can select a desired angle for turn-of-nut tensioning on the tool. 
     
     
         6 . The fastening system of  claim 1 , wherein the tool comprises an interface where a user can select the desired snugging torque. 
     
     
         7 . The fastening system of  claim 1 , wherein the tool comprises a visual indicator of final tensioning. 
     
     
         8 . The fastening system of  claim 1 , wherein when both the desired snugging torque and the final tensioning is applied to the fastener, the splined portion remains connected to the threaded portion. 
     
     
         9 . The fastening system of  claim 1 , wherein the splined portion has a diameter and the threaded portion has a minor diameter along the length of the threaded portion, wherein the diameter of the splined portion is relative to the minor diameter of the threaded portion. 
     
     
         10 . The fastening system of  claim 1 , further comprising at least one washer between the bolt and the nut. 
     
     
         11 . The fastening system of  claim 1 , further comprising a lubricant, wherein the resultant stress of torque applied by the tool at a location between the splined portion and the threaded portion is a function of a torque coefficient of the lubricant, wherein the resultant stress is below the ultimate stress of the shank at the location. 
     
     
         12 . A method of tightening a fastener comprising a nut and a bolt with a single tool comprising a first socket and a second socket, the method comprising:
 engaging the first socket with an outer surface of the nut;   engaging the second socket with the splined portion on the fastener;   rotating the first socket relative to the second socket to apply a desired snugging torque;   rotating the first socket relative to the second socket to apply final tensioning,   wherein the splined portion remains connected to a threaded portion of the fastener.   
     
     
         13 . The method of  claim 12 , further comprising selecting on the tool at least one of the desired snugging torque or the angle for final tensioning. 
     
     
         14 . The method of  claim 12 , wherein the first socket is rotated in a first direction and the second socket is rotated in a second direction opposite the first direction. 
     
     
         15 . A fastener for use with a single tool that provides both a desired snugging torque and a final tensioning torque, the fastener comprising:
 a bolt having a head and a shank extending axially from the head, the shank having at least one threaded portion and at least one splined portion, the splined portion defining an end of the bolt, at least one threaded portion between the head and the splined portion; and   a nut having an inner surface and an outer surface, the inner surface in threaded engagement with the threaded portion of the bolt,   wherein the bolt has a torsional strength at a junction between the threaded portion and the splined portion that exceeds both the desired snugging torque and the final tensioning torque.