Betty,
I purchased one of the Martilli cutters at the Harrisburg Quilt show last year. I use it all of the time. Just today I discovered that it needs to have its screw tightened left handed style. I was using it yesterday and it kept falling apart. I had my husband the "machininst" examine it as I thought the screw was stripped. He has plenty of those kinds of spare parts in our garage. It actually says right on it to tighten in the opposite direction. That solved the problem. I met the man who invented it at the Lancaster Quilt show this spring. It figures he is either an engineer or a man with a "machinist" background like my husband.
I like the cutter. It will cut through a lot of layers and is easier on my poor carpal tunnel hands.