ASME B18.2.6:2019 pdf free download – Fasteners for Use in Structural Applications
2.1.9.1 Thread Acceptability.Unless otherwise specified by the purchaser, gaging for screw thread dimensionalacceptability shall be in accordance with Gaging System 21, as specified in ASME B1.3.
2.1.9.2 Thread Length. The length of thread on bolts shall be controlled by the grip gaging length, Lg max., and thebody length, Ls min.
Grip gaging length,Lg, is the distance measured parallelto the axis of boltfrom the underhead bearing surface to thefaceof a noncounterbored or noncountersunk standard G0 thread ring gage, assembled by hand as far as the thread wilpermit. It shall be used as the criterion for inspection.The maximum grip gaginglength,as calculated and rounded to twodecimal places for any bolt not threaded full length, shall be equal to the nominal bolt length minus the thread length(Le max.=L nom.-Lz).For bolts that are threaded full length, L- max. defines the unthreaded length underthe head andshall notexceed the length of 2.5 timesthe thread pitch for sizes up to and including 1 in.diameter, and 3.5 timesthe threadpitch for sizes larger than 1 in.diameter.L max.represents the minimum design grip length of the bolt and may be usedfor determining thread availability when selecting bolt lengths even though usable threads may extend beyond this point(see Table 2.1.9.2-1).
Thread length, Ly, is a reference dimension, intended for calculation purposes only, that represents the distance fromthe extreme end of the boit to the last complete (full form) thread.
Body length, L p, is the distance measured parallel to the axis of the bolt from the underhead bearing surface to the lastscratch of thread, or to the top of the extrusion angle. It shall be used as a criterion for inspection.The minimum bodylength, as calculated and rounded to two decimal places, shall be equal to the maximum grip gaging length minus thetransition thread length (L; min.= L; max.- Y).Bolts of nominal lengths that have a calculated Lg min.length equal to orshorter than 2.5 times the thread pitch for sizes 1 in.diameter and smaller,and 3.5 times thethread pitch for sizes largerthan 1 in. diameter, shall be threaded for full length (see Table 2.1.9.2-1).
Transition thread length, Y, is a reference dimension intended for calculation purposes only,that represents the lengthof incomplete threads and tolerance on grip gaging length.
2.1.9.3 Incomplete Thread Diameter. The major diameter of incomplete thread shal not exceed the actual majordiameter of the full form thread.
2.1.9.4 Fully Threaded Bolt Diameter.The diameter of any unthreaded portion of a bolt considered fully threadedshall be between the minimum pitch diameter and maximum major diameter of the threads.
2.1.10 Point.Point shall be chamfered or roundedat the manufacturer’s option from approximately0.016 in.belowtheminor diameter of the thread.The first full formed thread at major diameter is located a distance no greater than 2 timesthe pitch measured from the end of the bolt.This distance is to be determined by measuring howfar the pointentersinto acylindrical NOT G0 major diameter ring gage (reference gage, see ASME B1.2).
2.1.11 Straightness. Shanks of bolts shall be straight within the following limits at MMC:
(a) For bolts with nominal lengths to and including 12 in., the maximum camber shall be 0.006in.per inch (0.006L)ofbolt length.
(b) For bolts with nominal lengths over 12 in. to and including 24 in., the maximum camber shall be 0.008 in.per inch(0.008L) of length.
A suggested gage and gaging procedure for checking bolt straightness is given in ASME B18.2.9.