It looks like you may be useing pine for yur puzzles. I use Popular it is easier to work with and the squareness of the blade is real important , I use an old combinaation square head to dheck squareness I use white paper in back of the blade and get the blade as square as I possibly can, The speed I use is on the high end, blades don't last as long but it helps and is worth the blade. do not force the blade and you will have no problem.
IKE