Well, cutting technique is one thing, grain orientation is another and different tools 'presentations' work better or worse. A scraping cut, with the edge at 90 degrees to the spin of the wood, is one cut, and a shear cut, with the edge at an angle to the rotation of the wood is another. The shear cut can be done with the bevel rubbing or not. If it isn't rubbing, then it is called a 'shear scrape' but isn't a scraping cut at all. Which cuts more cleanly? If you are cutting end grain (spindles or hollow forms) a scraper can to as good of a job as a gouge for hollowing purposes. For cutting spindles, I use a bevel rubbing cut most of the time, and some times I even pick up a skew. On bowls, you can't beat a scraper for heavy stock removal, but it doesn't leave a very nice surface. Most will use a gouge with a high shear angle bevel rubbing cut for a final pass. I always clean that up with a shear scrape, which again is at a very high shear angle, but not rubbing the bevel. This is better for removing small ripples that you could remove with 80 grit. Difficult to shear scrape the inside of a bowl with a gouge, so I use a ) nose shaped scraper. I prefer a shear scraped surface for sanding on bowls because no matter how delicate you are with the bevel rub, there is some burnishing. Also, rubbing the bevel generates a tiny bit of 'bounce/oval shape' in the bowl. Not critical unless you are going for less than 1/8 inch thick. You can get a piece as close to perfectly round by shear scraping as humanly possible, a very slight step up from how round you can get them with gouges: think 1/16 inch out of round, which translates to 1/32 plus/minus, which is very close. Scrapers work okay for sweeping across the bottom of bowls since you are not cutting down through the grain, but across it. Never use a scraper/scraping cut any where near the rim of a hollowed out bowl as "my bowl made this funny screeching and howling sound and then it blew up" vibrations will occur. Scrapers will generally cut more cleanly in harder woods than in softer ones. I don't use carbide scrapers. They won't do anything that you can't do with standard scrapers, and you can resharpen standard scrapers thousands of times before you wear them out... I prefer scrapers for shear scraping to gouges. I am starting to think that a lightly burnished edge rather than the grinder burr works a bit better, not for durability, but for a slightly sharper edge. The higher the shear angle, the cleaner the cut...
A bunch of random thoughts, but a shear scraping video should be coming this year... or next...
robo hippy