What you need is the old standard buttonholer made by Singer. It has cams and makes many sizes of buttonholes absolutely perfect every time. You can also adjust the width for larger thicker buttons. I have the older black model low shank model (circa 1950) that came with my Featherweight. After being totally frustrated trying to make buttonholes for my purses on my expensive Janome (wouldn't take larger or thicker buttons) I found that my ancient old buttonholer would fit and work on my Janome 6500!!! All you have to do is pop in the right sized cam, attach it and drop the feed dogs. I now have perfect buttonholes every time. Singer buttonholers are often available in thrift stores or at estate sales for $5 - $10. The newer models are tan in an oval green plastic case while the high shank slant models come in a dark rosy pink case.