Hi All,
I cannot resist my tuppenceworth on this subject.
My source of inspiration, and much of my knowledge has come from my sadly lamented good friend Bill Jones, whose books are in my opinion the best and most interesting books on turning you can lay your hands on - that is if you can, as they have now been out of print for some time. He reckons scrapers are people, not tools, though I cannot imagine what a negative rake person would look like. My experience is as follows;
I have used scraping, actually cutting, tools for a long time now on both hardwoods and alternatives. As per Bill's recommendation I remove any burr from the tool for these materials. Not removing it makes for a much more, and often too much more, aggressive cut. The burr should be left intact for softer materials. The negative rake for best use I find is controlled by the turner (scraper) by raising the handle until best results of cutting are obtained. Even with pre negative raked tools this may also help.
Just my input, which may be of help to some turner.
Have fun, cheers, John.