I have a 15” long 5/8”-11 threaded rod in a machine I’m building that’s being spun by a 3,600 RPM motor. The rod is held on each end with 10K RPM bearings and spun by a squared off end with a nylon gear over it with a corresponding nylon gear on the motor’s shaft (I’m gear driving, rather that direct driving due to a needed height difference between the components). Looking at it while it’s running everything appears to be in order, the gears mesh well, and nothing stands out as misaligned, but there’s more vibration and noise than I was expecting when I fire the machine up for fit testing.



While the rod LOOKS straight when I eyeballed it, someone suggested I check that the rod was truly straight with a roll test on a truly flat surface (I used a joiner) and there IS a very small amount of variation along the rod (less than a millimeter from “flat” at it’s worst point). I’m not completely convinced the rod is causing unnecessary vibration and that I’m going to have to accept a certain amount of noise / vibration connecting a 3,600 RPM motor to an empty metal box but I thought I’d ask here if anyone has any tips or tricks how to get a threaded rod truly straight other than "precision machine a new one, yourself".



Every video I’ve seen on straightening bar or rod is starting with stock that’s noticeably bent and the end result seems to be GENERALLY straight, but definitely wouldn’t pass the roll test so I’m wondering if anyone has any ideas on how to true up an ever-so-slightly wonky bar.


Any suggestions would be appreciated.


Thanks,


Scott


Read the full thread at metalworkforums.com...