I've been using a 5R or 7R depending and not have much problems. However, when it comes to finer cuts I'm moving to a 2R. However, I have found some sheets are just worse than others. I had one sheet that it didn't matter what blade or how thick the cuts the darn thing splintered and broke. I wound up using that sheet for backing only. My dad had a look at it and thought perhaps it wasn't actually baltic birch they had sold me.....