Slipping when pedalling I have a repair question. I am experiencing some slipping when I pedal, once-per rotation, however, it is not the normal chain/gear skipping that I have read about most of the time. The bike is an old steel frame Bianci, with 18 gears. 

The slip is subtle, less than one chain link for sure, accompanied by no audible noise or jarring.  I can only "feel" it through my feet in the pedal.  Also, it does NOT have to do with how hard I am pedaling, if I pedal slowly while rolling so that its freewheeling, I can still feel the slip, which feels like a different "texture" while pedaling. I hope that makes sense, I cannot think of a better way to describe it. It seems to not happen all the time (about 80%), but I have not been able to correlate when it happens to a specific gear combination for example. 

I tightened all the bolts on my chainring and in the rear derailleur, but that did not fix it. Does anyone have any idea what could be causing this? 

Thanks for the help!
Drop the chain and try to rotate cranks. If "skip" feels then I would look into BB. If not, then pretty much sounds like kink in the chain which is very possible on very new or very old chains.

Very new chains can be over-pressurised while installing and therefore one link connection is just not flexible enough which makes it "skip" when going through the derailer. Old chains have rust and dirt problem which causes same problem.