■ Bolt ＆ Nut and Torque Explanation※ TORX and Torx are registered trademarks of Acument Intellectual Properties LLC.Hexagon Bolt / Hexagon Nut Bolt & Nut ExplanationThread StandardsVarious Head ShapesHexagonboltHexagon sockethead cap screwTorx screwSlotted head screwCross head screwSquare boltTorque ExplanationAcross at width Hexagon bolt is a bolt whose head shape is hexago-nal, and hexagon nut is a hexagonal nut.The size of the tool for tightening hex bolt or hex nut is based on the "across at width" which is the width dimension of the hex opposite side.Specify the tightening tool size with the across at width.Torque is the force to rotate an object. It is the power to turn a spanner or wrench when tightening or loosening a bolt or nut, and is also called "tightening torque" when tightening a screw.The tightening torque of the bolt is proportional to the nominal diameter of the bolt and the axial force of the bolt, and is expressed by the following equation.Torque coecient indicates the resistance of the bearing surface or screw surface of the bolt to be tightened, and changes depending on the condition of the contact surface. For example, applying a lubricant to the threaded surface will lower the torque coecient value and require less torque to achieve the same axial force.Nominal diameter of the bolt indicates diameter of the thread.Axial force of a bolt is the force that clamps the member to be tightened with a bolt, and is also called bolt tension or tightening force. Essentially, bolt tightening means tightening this tightening force (= bolt axial force) to a prescribed value, but it is dicult to tighten while measuring the bolt axial force, so it is substituted by a tightening torque that is easy to measure.The dimensions of the bolt parts are as shown in the gure.The nominal thread diameter is φD, the nominal length is L, and pitch which means the distance between threads is P.The nominal diameter φD of the screw is the maximum diameter of the screw portion. It expresses the outer diameter of the screw thread portio in mm, and "M ○○" with M attached to the head of this nominal diameter is determined by JIS. For example, if φ D = 10 mm, the screw is called "M10".Nominal length L represents the distance from the head bearing surface to the screw tip. Pitch P is the distance between the thread and the thread, and there are coarse pitch as standard and ne pitch. Fine pitch screws are displayed as "Nominal diameter x pitch x nomnal length" like "M10 x 1 x 50". On the other hand, coarse screws omit the indication of pitch.Threaded portionHexagon bolt Across at widthHexagon nutAcross corner widthAcross Flat WidthAxis diameter φ dPitch PPart name of screwNominal diameter φ DNominal lengthLengthThe tightening torque=torque coecient x bolt nominal diameter x Bolt axial forceBolt axial forceBolt tension==Tightening force Tightening torqueBolt headBolt bearing surfaceThreadNut495
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