Yes, you should be able to disable the knife. But, I would also wonder why you would want to. If you are frightened of cutting off too much, just sew slowly and carefully. If you disable the knife and you have too much fabric in your edge that the serger is trying to sew over, you may end up with it not sewing properly and having missed stitches. The knife cuts off just the right amount so you have a nice flat edge. Sometimes, depending on what I'm sewing, I serge so that the edge of the fabric is just on the knife and it barely takes just some fluff off. You could try that if you are worried about cutting too much off. Once you get used to your serger you will love it
