INFI & Thin Edge Geometry

PeterPHWS said:
...So maybe what you are cutting with is not perhaps the best recipe for success and longevity from a blade? Or, are you sure you are going that thin?
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I read a lot of these thin edge threads and people are often making claims about their thin edges being so many degrees: X degrees per side/ 2X degrees inclusive. How are you/they accurately measuring this ? Anyone got a laser reflecting goniometer ?

http://www.catra.org/pages/products/kniveslevel1/lgpm.htm
 
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shunsui said:
Anyone got a laser reflecting goniometer ?
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Yes, doesn't everyone??


Actually, that's not quite accurate - I used to use one, but I quit that lab, and it wasn't laser based, but an ellipsometric goniometer. But you get the point.





:D
 
shunsui said:
I read a lot of these thin edge threads and people are often making claims about their thin edges being so many degrees: X degrees per side/ 2X degrees inclusive. How are you/they accurately measuring this ? Anyone got a laser reflecting goniometer ?

http://www.catra.org/pages/products/kniveslevel1/lgpm.htm
Click to expand...

For flat edges you can simply measure with a caliper and do some trig. Take multiple points on the edge and average it for better accuracy. Some people have sharpening systems that tell you what angle you are sharpening at. On my EdgePro the marked angles correlate almost perfectly with my caliper measurements.

And of course you can use lasers for convex edges.
 
shunsui said:
I read a lot of these thin edge threads and people are often making claims about their thin edges being so many degrees: X degrees per side/ 2X degrees inclusive. How are you/they accurately measuring this ? Anyone got a laser reflecting goniometer ?

http://www.catra.org/pages/products/kniveslevel1/lgpm.htm
Click to expand...

I lay something flat along each side of the bevel and measure the angles with a protractor. Low tech and won't work for convex edges, but it gives you ballpark measurements. That's why I usually write 8-10 degrees per side. When I go to microbevel my knives on my sharpmaker set at 15 degrees per side and the SM rods don't even come close to touching the whole bevel, I know it's got to at least be 12 degrees or thinner, so my measurements may not be exact but they're close enough for practical discussion IMO.
 
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This and a pair of 2X magnification glasses from Walmart work wonderfully well. Secure the knife in an edge-up position, scissor the inside edges (plate and arm) down until they're laying flat against the edge bevel on both sides, and take a look at the angle. The glasses aren't absolutely necessary, but they save a lot of squinting. Actually, I've been wondering about finding some 3X magnification versions...

st306411.jpg
 
shunsui said:
I read a lot of these thin edge threads and people are often making claims about their thin edges being so many degrees: X degrees per side/ 2X degrees inclusive. How are you/they accurately measuring this ? Anyone got a laser reflecting goniometer ?

http://www.catra.org/pages/products/kniveslevel1/lgpm.htm
Click to expand...
I have this one
http://www.catra.org/pages/products/kniveslevel1/lkep.htm
I also have used dial/digital calipers and online calculators.

I have been sharpening my folding knives to 12 degrees per side (setting the bevel on an adjustable hone rest, measurements again made with trig) because I like the level of durability and cutting ability at that level. I am not as careful as Vivi, and I have been reading his posts, looking at his pics, and watching his vids for a few years. I am too clumsy around concrete floors and steel objects to want to go to single digit angles, but I know 24 inclusive is pretty good for small knives as I us them.

Cold chisels for cutting soft metal are about 25 degrees per side.
 
For my Fatty Busse Game Warden .27, which is basically an isosceles triangle I cut it in half (figuratively) to form a right triangle and plugged the numbers in here http://www.csgnetwork.com/righttricalc.html Then I pretty much know what angle I have when I am using the Edge Pro( -7 Deg. per side ). 17Deg. back bev. 20 Deg. edge bev. per side(approximately).Sharpened with 320 stone 1000 stone 3000 polish tape then 7000 polish tape then I cut up some .3 mic. tape from woodcraft and did 50 passes each side w/that. I whittled my first hair the other day, but that was when it was only at 17deg, hadn't ground in the 20deg edge at that point. I just can't seem to get the edge back to that sharp since I set it to 20deg. Should I go thinner?
 
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I just cleaned the stones. Rubbed them on 2000 grit wet/dry sand paper on glass cutting board. Then made 5 passes on each side with each stone. Big difference! Still won't whittle hairs but shaves hair off arm with ease. Don't over look the fundamentals:)
 
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