I am planning on building a straight timber staircase from pine. I recently had the wood sawed into 4 X 12 stringers and 3 X 11 treads. The wood is green but I have to build very soon. What method of joining the treads to the stringer should I use. I was thinking of simply lag bolting the through the stringer into the treads but I don't think this will be very tight. Ideally I would like put threaded rod through both stringers and the treads but drilling a straight 48" hole would be very hard.Should I make tenons on the treads and mortices into the stringers and then use lag bolts and glue. Thanks for any help.

Do some research on the net and thru you local lumber yard. There is a German stainless steel product and system for hanging stair treads which out performs any other known to man at this time. All you need is some careful measuring/marking, a drill and a screwdriver.
good luck
deralte

you can cut simple slots in the stringers for the treads(3/4 or 1" deep) then use threaded rods(48") to pull the stringers together. place the threaded rod under the top, bottom and center treads.... you could tighten up the stairs after they dry....