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I was looking at scrapers and some of them mention their Rockwell Point value. Pertinent information from that page:

They are a nice complement to our other scrapers and just a couple of Rockwell points harder (Rc51-53) to compensate for their lack of thickness. Scrapers measure 2" x 6" (50mm x 150mm).

My questions in that regard:

  1. What are Rockwell Points?
  2. How are they measured (How do you determine a given objects Rockwell Points)?
  3. What effect would a cabinet scraper have if it was "harder" (Had a higher point value)?
StayOnTarget
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Matt
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1 Answers1

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Despite the difficulties of the link, I think it is referring to the Rockwell hardness scale.

The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload.1 There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale

As far as the effect of the hardness.

First the harder metal is the longer it will generally hold a sharp edge. So less sharpening involved. Also the hard a metal becomes the more brittle it becomes. This means that the edge could more easily chip or the entire scraper could snap/break.

So as far as actual use, you might be able to use it to do more on harder woods with less sharpening, but you have to be more careful about chipping/breaking it. These are fairly thin pieces of metal so the temper probably needs to be in a relatively small range to keep an edge and to be flexible. better tempering techniques will allow it to be harder toward the edge while leaving plenty of spring in the rest of the tool.

bowlturner
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  • FYI I added another sub question to give this QA a little more substance. More than just making a question for the sake of making a question. – Matt May 29 '15 at 14:55
  • @Matt added more to deal with item #3 – bowlturner May 29 '15 at 15:07
  • Ah ok.. So just getting the hardest metal is not the best idea. It all depends on what you are working with. – Matt May 29 '15 at 15:37
  • @Matt This is my understanding from metal work and woodwork, not experience using scrapers. But I think I'm mostly right. – bowlturner May 29 '15 at 15:38
  • Mostly should be good enough :) – Matt May 29 '15 at 15:42
  • Softer metal will both dull faster and sharpen more easily. What hardness is ideal depends on how you use and sharpen the tool. – keshlam May 29 '15 at 15:43
  • @keshlam That's true too. I'm used to turning where I want my tools to hold the edge as long as possible between sharpenings, since the time to resharpen is not much different with a grinding wheel, but taking fewer breaks to do it is the time saver. – bowlturner May 29 '15 at 15:46
  • I've always been afraid of grinding wheel ruining a tool's temper (changing the hardness). There's less risk of that with the slower and water-cooled wheels... Sharpening is definitely a skill I need to improve. – keshlam May 29 '15 at 16:05