like the other guys said, I use a new sharp utility knife blade that I have wiped off with a clean rag soaked with denatured alcohol..the blades usually have some oil on them..I have a yellow pine 2x6 that is 48 in long that I cut veneers on, I use a 48inch metal straight edge and use 3 or 4 C clamps to hold straight edge from moving during cutting..I dont try to cut all way thru the first pass, I cut about have way thru first 2 passes and may take 4 to cut all way thru..if you rush it your blade might follow the grain not the straight edge and you will not have a straight cut..I use 1.75 or 1.5 inch fiberglass cut offs to set the cut widths..