Fussy Facts About Torquing Fasteners
Dec 15, 2013
Some of you who rebuild engines already know this, but even if you don't build engines, it never hurts to "know more than you can use."
In a perfect world, bolt manufacturers would prefer that nuts and bolts be installed with their thread lubricated unless specifically directed that the fasteners be installed "dry." If lubrication is recommended, use ONLY the type of lubrication recommended. Different lubricants have different coefficients of friction. A bolt lubed with WD-40 will produce incrementally different torque values than a bolt lubed with 30-weight engine oil.
That's no big deal if you're tightening the bolts that hold disk ripper points in place, but if you're assembling the connecting rod caps in an engine, it's a BIG deal. Connecting rod manufacturers assemble and precisely torque the big ends of connecting rods BEFORE final machining, so that the finished bore is absolutely round. When the connecting rod cap is removed for shipping, the metal relaxes and goes microscopically out of round. When an engine builder installs the rod in an engine and bolts on the rod cap, it is critical that the rod cap bolts be installed using the same lubricant so the same exact torque will pull the components back into "round."
Few nuts and bolts in farming are as fussy as those in engine building, but the connecting rod example highlights the possible variances that could distort torque readings when installing nuts and bolts. It's up to the individual mechanic or farmer to decide if the particular repair requires the precision of torquing every nut and bolt to exact value, but...if never hurts to understand mechanical theory so you can make an educated decision about how to make repairs on your farm.