I went to a rotary cutting instruction class long ago at a fabric shop. An Olfa rep was vending and demoing Olfa products. She said when cutting with the rotary, always push down to the floor like the blade is going into the floor not run along on top of it. And the smaller the blade the less pushing the fabric forward when cutting. If the blade will not cut through two layers of fabric with very little effort then the blade is dull.