But the tightening torque does not increase above a certain value even if the tool is driven for a long time. (See Fig. 17, 18, 19 and 20) (3) Diameter of bolt The tightening torque differs with the diameter of the bolt as shown in Fig. 17, 18, 19 and 20. Generally a larger diameter bolt requires larger tightening torque. (4) Tightening conditions The tightening torque differs according to the torque ratio, class, and length of bolts even when bolts with the same size threads are used. The tightening torque also differs according to the condition of the surface of workpiece through which the bolts are to be tightened. When the bolt and nut turn together, torque is greatly reduced. (5) Using optional parts (WR12DM2, WR9DM2) The tightening torque is reduced a little when an extension bar, universal joint or a long socket is used. English (6) Clearance of the socket (WR12DM2, WR9DM2) A worn or deformed hex. or a square-holed socket will not give an adequate tightness to the fitting between the nut or anvil, consequently resulting in loss of tightening torque. Using an improper socket which does not match to the bolt will result in an insufficient tightening torque. Matching socket and bolt sizes are shown in Table 4, 5, 6 and 7. (7)Tightening torque varies, depending on the battery’s charge level (WR12DM2, WR9DM2) Fig. 22 and 23 show an example of the relationship between tightening torque and the number of tightenings. As shown, tightening torque gradually weakens with the increase in the number of tightenings. In particular, as the torque decreases very close to the complete discharge (“a” margin in graph), the unit’s impact weakens, the number of time impacts declines and tightening torque drops off abruptly. If this occurs, check torque level, then recharge the battery if necessary. kgf·cm 15/32".1-3/4" kgf·cm 9/16".1-15/16" N·m N·m (in-lbs) (M12.45) (in-lbs) (M14.50) 1400 140 140 1400 High strength bolt 60 Ordinary bolt Tightening torqueHigh strength bolt High strength bolt Ordinary bolt 120 120 1200 1200 kgf·cm N·m 3/8".1-5/32" (1042) (1042) (in-lbs) (M10.30) (1215) (1215) 100 100 100 1000 1000 Tightening torque (347) (347) (347) Ordinary bolt 200 20 20 20 200 200 (174) 0 (174) (174) 0 0 0123 0123 0 0 0 0 1 2 3 Tightening time: sec Tightening time: sec Tightening time: sec (Steel plate thickness (Steel plate thickness (Steel plate thickness t = 3/8" (10 mm)) t = 1" (25 mm)) t = 1" (25 mm)) Fig. 17 1000 (868) (868) (868) 80 Tightening torque 80 800 800 80 800 (694) (694) (695) 60 60 600 600 600 (521) (521) (521) 40 40 40 400 400 400 English kgf·cm 15/32".1-3/4" N·m (in-lbs) (M12.45) 120 kgf·cm 5/16".1-3/6" kgf·cm 3/8".1-3/6" 1200 (1042) N·m N·m (in-lbs) (M8.30) (in-lbs) (M10.30) 1000 100 100 100 1000 1000 Ordinary bolt High strength bolt Ordinary bolt High strength bolt (868) (868) (868) High strength bolt 80 Tightening torque 80 80 800 800 800 Tightening torque Tightening torque Tightening torque (694) (694) (694) 60 60 60 600 600 600 (521) (521) (521) 40 40 40 400 400 400 (347) (347) (347) 20 200 20 200 200 20 (174) 0 0 0 1 2 3 Tightening time: sec (Steel plate thickness t = 3/8" (10 mm)) kgf·cm3/8".1-5/32" (in-lbs) N·m (M10.30) 2000 200 High strength bolt Ordinary bolt Tightening torque (1736) 150 1500 (1302) 100 1000 (868) 500 50 (434) 0 0 (174) (174) 0 0 1 2 3 0 1 2 3 0 0 0 Tightening time: sec Tightening time: sec (Steel plate thickness (Steel plate thickness t = 1" (25 mm)) t = 1" (25 mm)) Fig. 18 kgf·cm15/32".1-3/4" kgf·cm9/16".1-15/16" N·m N·m (in-lbs) (M12.45) (in-lbs) (M14.50) 2000 200 High strength bolt Ordinary bolt 200 2000 Highbolt strength Ordinary bolt Tightening torque (1736) (1736) 150 150 1500 1500 (1302) (1302) 100 1000 100 1000 (868) (868) 500 50 500 50 (434) (434) 0 0 0 0 0 1 2 3 0 1 2 3 0 1 2 3 Tightening time: sec Tightening time: sec Tightening time: sec (Steel plate thickness (Steel plate thickness (Steel plate thickness t = 3/8" (10 mm)) t = 1" (25 mm)) t = 1" (25 mm)) Fig. 19 English kgf·cm N·m 15/32".1-3/4" (in-lbs) (M12.45) 1400 140 Higbolt h strength Ordinary bolt (1215) kgf·cm 5/16".1-3/6" kgf·cm 3/8".1-3/6" 120 N·m N·m 1200 (in-lbs) (M8.30) (in-lbs) (M10.30) Tightening torque (1042) 100 100 100 High strength bolt 1000 1000 1000 (868) 20 Ordinary bolt High strength bolt 20 (868) (868) Tightening torque Tightening torque 80 80 80 800 800 (694) 600 (521) 400 (347) 200 (174) 800 (694) (694) 60 60 60 600 600 (521) (521) 40 40 40 400 400 (347) (347) 20 200 200 (174) (174) 0 0 0 0 0 0 0 1 2 3 0 1 2 3 0 1 2 3 Tightening time: sec Tightening time: sec Tightening time: sec (Steel plate thickness (Steel plate thickness (Steel plate thickness t = 3/8" (10 mm)) t = 3/8" (10 mm)) t = 1" (25 mm)) Fig. 20 Bolt Steel plate *The following bolt is used. thickness t Ordinary bolt: Strength grade 4.8 High tensile bolt: Hardness division 12.9 Explanation of strength grade: 4 — Yield point of bolt: 45,500 psi (32 kgf/mm2) () 8 — Pulling stre...
