The standard type of long bladed scissors has just the right amount of width (thickness) for what you are looking for with no guessing . Stick the blade (one) of the scissors in the eyelet of the needle till it stops , slightly pry up and out toward the opening and pull the blade through the opening this will open the eyelet just enough to do what you need to do dont worrie to much about the size of the opening because you are just trying to get the blade to just fit through the eyelet . It will be the size you need but do this only once as to not open it to far this is good for the round eyelet needle bars the tapered ones like stated above dont need it but arent good for the bearings . As for the comment on not needing to bend the eyelet i use standard sized nips on my machines and i use some of the best needles of several brands in the industry and i have to bend every needle (except tapered) i use on every machine i have ! So to bend or not to bend ....it a matter of preference , style , and need ! Have a nice day !!!