I have a Carter strip pump M4889. It has 5/16 inlets. Is there a tap available to enlarge the opening to install my 1/2 inch line?

Milan

I need a 3/8 PT tap. is is hardware store material?

Could be... try checking your local hardware store. I can't quite see their shelf from here. ;)

If not, try an auto parts store; especially NAPA.