Just Steve

I am brand new to scroll sawing. I have done other woodworking for years but wanted to try my hand at smaller more marketable projects. I love the look of detailed fret work or intarsia. I have a scroll saw that my research says was made in 1951. It is a craftsman 20 inch with a 4 step pulley belt drive. The lower blade holder works off a gear box and travels straight up and down. (no arm) The upper blade holder is at the end of the upper frame and is merely a spring loaded sleeve with a clamp that is depressed down and tightened on the blade. All the scroll instruction videos I watch emphasize blade tension. The blade will make the high "ping" when I install it, but after a cut or two the tone changes, even though the blade is still clamped just as deeply in the blade holders. Also I am not having much luck getting it to follow a line in my attempts to "practice" using on-line available patterns. It's not so bad on the straight line, only wandering a little, but when I try to get it to turn it seems to have a mind of its own. First it won't turn, then all of a sudden it make a hard turn and oversteers the line badly. I am trying a few blades as I heard some blades are made to overcome "set drift" of the teeth. My first "play" with the saw after I got it set up on a stand and the right belt for it was the best. I had no pattern as was just seeing what it would do on a scrap of 1/4 inch sandiply, and with home center blades. (I think they were skil brand) It cut tight turns and pretty much responded to my attempts to change direction when I wanted. My practice patterns have been on 1/2 plywood with #5 PS wood super sharp blades. Am I wasting my time on this machine since it does not have fixed tension on the blade, or will enough patience and practice allow me to do the detail work needed to make salable projects? I know intarsia pieces have to fit together right. I am sure I could use this machine to make free hand jigsaw puzzles, but to get it to follow a pattern reliably I am not so sure of.