D
DPellegrin
Guest
Gentlemen,
I don't think we are assembling swiss watches here. Torque wrenches have worked just fine for decades. I have visited the DDC Series 60 assembly line in Redford, Michigan, the the Cummins NT855 assembly line in Columbus, Indiana and have seen many torque wrenches in use at those places. In fact, When DDC does durability testing they precisely measure the wear components in an engine then assemble it by hand employing a torque wrench. I have rebuilt many DDC Series 71 and 92, Cummins NT 855, and CAT 3306 and 3406 engines all using a torque wrench with no problems. I believe the engineers that specify a given torque for a given fastener build in a safety factor for nominal friction characteristics.
If you know the fastener diameter and the tread pitch you can calculate the fastener strech per degree of rotation. This results in the amount of clamping force between the parts. Cummins used to call this the "torque-turn method" of tightening a fastener. The only time I have heard of this being used was on the 1" diameter main bearing cap bolts on the 855 engine. Later Cummins dropped this requirement and specified a torque of 310 lb. ft. for these bolts.
I don't think we are assembling swiss watches here. Torque wrenches have worked just fine for decades. I have visited the DDC Series 60 assembly line in Redford, Michigan, the the Cummins NT855 assembly line in Columbus, Indiana and have seen many torque wrenches in use at those places. In fact, When DDC does durability testing they precisely measure the wear components in an engine then assemble it by hand employing a torque wrench. I have rebuilt many DDC Series 71 and 92, Cummins NT 855, and CAT 3306 and 3406 engines all using a torque wrench with no problems. I believe the engineers that specify a given torque for a given fastener build in a safety factor for nominal friction characteristics.
If you know the fastener diameter and the tread pitch you can calculate the fastener strech per degree of rotation. This results in the amount of clamping force between the parts. Cummins used to call this the "torque-turn method" of tightening a fastener. The only time I have heard of this being used was on the 1" diameter main bearing cap bolts on the 855 engine. Later Cummins dropped this requirement and specified a torque of 310 lb. ft. for these bolts.