Does flour manufactured in the US need sifting? If yes, what mesh sifter is needed?
This is what one of the Rabbonim of the CRC of Chicago answered regarding your question.
“If the flour was purchased from a store that has proper storage conditions, and was properly stored by the consumer, then the letter of the law doesn’t require one to sift. There are those who wish to be extra strict and sift or check a sample of the flour just to be sure”.