But nowhere is my body (hand/eye coordination) precise enough to use this device to measure blade thickness exactly behind the edge. For my blog, where I measure blade thicknesses, I measure them at 5 mm behind the edge. And of course this isn’t exactly 5 mm behind the edge, but an approximation.
So I wondered how people who give measurements of their blade thickness right behind the edge do this. Do they use different equipment?
I thought that the right place to check it would be at the bottom of the bevel, because this is where thickness becomes a factor in a blades ease of cutting.
I tried using my calipers, but it seems a little awkward, as you really want to measure right at the end of the instrument and I’ve never had much confidence in my calipers out there at the tip.
This year I bought a 1" micrometer from Grizzly for $13. http://grizzly.com/products/0-1-Micrometer/W2504 Maybe not the best quality, but I find it accurate to 0.0001 inches. Set the opening at a very small setting, then rest the edge in the gap and slowly open the micrometer until the edge drops down into the opening. Voila! Le measurement!
Sorry 'bout the metric thing. Surely somewhere the Chinese are selling a metric version. Grizz has a digital inch/metric version for $50.
in depth on bladeforumsThis has been discussed pretty, so maybe that thread will help you out =)
Understanding what terms are being used helps a lot when discussing this topic… please refer to the charts here. I use the western understanding of the terminology whereas you will use the european terms (like Murray Carter).
So using the terms you are aquainted with, the thickness of the edge refers to the thickness at the “shoulders” of the edge, or in other words, the point at which the primary edge transitions into the secondary edge.
Where this becomes obscured is when you start talking about convex edges, which is why some people (like knifemaker Joe Calton) have advocated measuring at a certain depths into the blade to have a standardized way to tell cutting ability. So I would say that it would not be bad to measure at 5mm into the blade from the edge, I would also measure the transition point though.
That seems like a do-able method, Tom! My caliper is a bit more fiddly than yours, but I’d never thought of using it the way you describe. I’m gonna try it tonight!
You’re right about the need for using the correct terminology, Josh. Particulary when we’re talking about something rabbit-holy like sharpening. (Funny that you can be called a Murray Carter adept if you don’t - I read the Bladeforums thread.) I indeed mean the thickness at the shoulders of the (primary) edge.
- I read the Bladeforums thread.) I indeed mean the thickness at the shoulders of the (primary) edge.