Since their inception ages ago, negative rake scrapers have undergone a resurgence in popularity. And for good reason. They're smooth-cutting and less aggressive than the mainstream scrapers many turners are familiar with. Keep reading for an assortment of our favorite negative rake resources, tips, and sharpening techniques.
Woodturning Negative Rake Scrapers Explained: Basics & How to Use
Beginners Guides
There are many schools of thought regarding negative rake scrapers, included angles, and techniques. We've provided two of our favorite introductory videos offering varying perspectives.
Beginners Guides
There are many schools of thought regarding negative rake scrapers, included angles, and techniques. We've provided two of our favorite introductory videos offering varying perspectives.
Included Angles: what's the magic number?
Negative rake scrapers are ground with a top and bottom angle - and the sum of these is called the included angle. As with any tool grind, different turners prefer different negative rake included angles. However, most agree that an included angle greater than 80º will not perform well, and anything greater than 90º won’t cut at all.
The general idea is that a larger included angle creates a less aggressive tool. On the other hand, a lesser included angle provides a finer finish. Cindy Drozda suggests 75º or less, and Stuart Batty uses a 50º included angle.
Our personal preference is an included angle of 65º (all our negative rake scrapers are ground to this degree). To create this angle, the top angle is ground to 25º, and the bottom to 40º.
In-Depth Introduction: article by Cindy Drozda
Thorough and easy-to-ready, Cindy Drozda's article covering the basics of negative rake scrapers is hard to beat.
Sharpening: restoring the burr
I find it helpful to begin the sharpening process by setting one of my grinding platforms to the top angle (I prefer 25º) and the second platform to the bottom angle (in my case, 40º).
This allows me to quickly touch up the tool as needed, without further platform adjustments between the two angles.
If you'd like to double check that you're replicating the factory grind, I suggest coloring the cutting edge of the tool with a sharpie pen. With the machine turned off, lay the scraper on the grinding platform and rotate the wheel by hand.
If the wheel is removing the mark, you'll know you have the correct angle. If not, adjust the platform until the mark is removed. You can also check the angle with a protractor.
Once you've established your angles, turn on the grinder and rotate the scraper back and forth, with your thumb firmly holding the tool in place, to restore the edge.
Keep in mind that it's critical you sharpen the top edge first, and the bottom edge last. This will ensure you're left with a burr on the top. After sharpening, you should be able to feel the burr by lightly touching the top of your scraper.