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Background Information and CATRA Curves
Make sure you read Part 1 first so that you understand all of the background information for this article.
Month: November 2018
Which Steel Has the Best Edge Retention? Part 1
Thanks to Mark McKinley and Alfredo Faccipieri for becoming Knife Steel Nerds Patreon supporters!
CATRA Testing
I previously wrote an article on what CATRA testing is and what it is revealing from a set of tests on 154CM: Maximizing Edge Retention. The CATRA edge retention test uses the slicing of 5% silica-impregnated cardstock and therefore tests slicing edge retention. A standard test uses 60 cuts with a fixed load and slicing length and the amount of cardstock cut per slice is recorded. The edge retention is then often reported as the total cardstock cut with all 60 cuts, and given as TCC (total cardstock cut) in mm. I shared this same CATRA test video in the earlier CATRA article to see the test in action:
Rockwell Hardness is the Megapixels of Knife Steel Specs
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Hardness and Megapixels
In the early-to-mid 2000’s with digital cameras and somewhat more recently with smartphone cameras we had the battle of megapixels. The number of megapixels is simply the number of pixels that are captured by a digital camera. When we had 0.3 megapixel cameras the pictures were quite blurry and jumping up to 2 or 3 megapixels made a big difference. However, when comparing 5 to 7 megapixels the quality of the image was much more likely to be controlled by the quality of the lens and sensor than simply the number of megapixels. Despite that, megapixels became an easy marketing point because it is a simple number to present to the public. We haven’t seen rockwell hardness climbing for no reason other than marketing, but it is one of the few simple numbers that are used to advertise for a knife. Therefore it is often misunderstood by knife buyers, and yes, even some knife makers. In this article I cover some simple reasons why hardness is not as important as other factors for predicting most steel properties. And then we get into the nitty gritty with why hardness is not always the same as strength and how heat treatment can affect strength independent of hardness.
All About D2 Steel – Development, Use in Knives, and Properties
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Update 10/22/2020: I now have an article with how to heat treat D2, PSF27, and CPM-D2 and it also includes toughness testing of each steel and edge retention testing of D2. https://knifesteelnerds.com/2020/08/31/how-to-heat-treat-d2-psf27-and-cpm-d2/