|
720Deere, fine threaded bolts won't offer any advantage for flywheel bolt applications... [They won't hurt either] ~While it's true that fine threads offer more clamping force [for a specific torque value] it doesn't offer any more clamping force if the torque on the coarse thread is raised to equal the same force..That's why there are different values given in the torque charts for both fine & coarse threads. ~The 2 big advantages of fine threaded bolts are: more bolt cross section at the thread area & a little less likely to work loose under vibration. There are a few lesser differences like ease of tapping hard material & more threads per inch in thin material. ~For use as flywheel bolts there would be little if any gain with fine threads...Both the fine & coarse thread bolts can be torqued tight enough to stretch the bolts [so there is no gain there]... It has more to do with bolt grade than thread pitch.. ~Both the fine thread & coarse thread bolts can be tightened enough to crack a flywheel so there is no gain there. ~As far as better vibration holding: I haven't ever seen a properly torque coarse thread bolt come loose on a 2-cylinder Deere.. ~Just use what you have access to [you probably want at least grade 8] ... Don't over torque either thread of bolt or you could crack the flywheel.. Check the flywheel bolt torque a few times after the tractor is run a while & you shouldn't have any trouble with either bolt thread... ~Remember the original bolts were more like a grade 3 or 5 [unmarked] & those worked for years if not over-tightened....
| 
