COUPLINGS

Set Screw and Length of FitBecause of the widespread use of zinc die casting or ironsintered alloy as internal thread material, the allowable load ofinternal thread decreases, and which can be a source of trouble.However, it can be solved by increasing the thickness of internalthread part. The relationship between length of fi t and materialstrength is described below.Strength of internal thread and set screw length of fitLower limit of length of fit [mm]15105External thread outside diameter= JIS 2 Class maxPitch diameter of internal thread= MIN=Allowable shear stress of internal thread [N/mm 2 ]=98=147=196=294=392 Accuracy of Fit Between Shaft and Hub or Flange BoreAs indicated below, shaft holding power does not decreaseuntil shaft accuracy of h9. However, the effect of fi t accuracy isexpected in the actual use environment.Fit accuracy with bush bore and shaft holding powerDecreasing rate of shaft holding power1.00.5Reference:h7h8h9h1020 40 60 80 100 120Fit gap between bore and shaftSocket screw group technology“How to select and use hexagon socket set screw”Shaft diameter 15M5 Concave pointM5 Flat pointh11M3-98 M4-216 M5-441 M6-735Nominal designation-Tightening torque [N·cm] Off-center Amount of Internal Thread BoreIf the internal thread bore is not centered from the shaft center,the shaft holding power may decrease. The following is theexamination results using M4 set screw.Off-center amount of set screw bore and shaft holding poweraSet screw=M4Shaft diameter= 101.0Decreasing rate of shaft holding power0.50 1 2 3 4 5Off-center amount a [mm]TechnicaldataAtención al Cliente - 902 208 608109