I have been using this knife for scraping. It does a beautiful job but it's hard on my arthritic hands. I made the handle in hopes it would be easier on me. If I put a squared off proper "scraper" blade in it it works, just OK. I thought I would make a knife blade for it so it would be like the knife only easier on my hands. It chatters when I scrape with it. The knife never chatters. Any ideas what would cause this?