Plywood that's been wet falls apart when cut ,i get free wood from the dumpsters and cabinet shops ,bulk pick up ,friends etc.3/4 " plywood will slow down your cutting speed so its a good thing to practice on .thin woods 3/8 1/4 and 1/8 cut very fast so slow your machine down and cut slow while holding the wood down to keep total control of where the blade cuts.you'll fond that one of your fingers acts as a pivot point for all your turns,etc.Fir woods are very soft and fragile .I don't like using them because of breakage.hope this helps!