Scary Sharp? Shaving Sharp?

I should mention that grinding a full convex grind is not for the impatient types...it can really test your stamina. Takes forever to get the grind even.

Maybe this will help explain.

The best way I've found to make a full convex grind is to make a full flat grind first - leaving the spine thick. Then slack-belt grind it pressing the whole blade against the belt. This will take quite a bit off the spine. What you are left with is long gentle arc with no flats at all. It's at its thickest about 3/8" down from the spine (but it's still no fatso...;))
 
Dan,

You still the man.

OK I'm gonna build me one of those.

Now staying on topic of scary sharp. I have one other blade geometry I've been itchin' to try:

Hollow ground back, chisel ground front. Some Japanese kitchen blades have this. There is no cutting drag on the back, cause it arcs away from what ever you're cutting. Chisel grind for a 20 degree (equivalent to a 10 degree double bevel :eek: ).

I think I'll try one of each in a small version first. Just to see. Probably in S30V so it'll hold up.

Hmmmm, thinking about it: your convex edge still might be a better cutter. Once the cut is complete the material is moving away from the blade and you have a heavier blade.

Hey!!! How about hollow ground back and convex front.

Oooohhh baby.

Steve
 
steve: convex edge on my spydie ss dragonfly... did it last in july(30th or 31st)... had to hit the strop thursday, had a few spots on the edge.
 
Dan,

I use a very similar procedure to grind hunting and utility blades from 1/8 stock D2 and S30V. The only difference is that I keep the blades tilted just a little on a fairly tight belt so that the curve comes out very shallow. With thin stock this works very well. I have shaved with knives ground this way from 3/32 stock, both from S30V and from D2. I have never seen knives any sharper than these get.
 
Steve,

I'd sure like a rotary platen from Frink. But I think I'm gonna try this convex stuff with a mouse pad on the platen and graphite belt cover.

Hope that's convex enough.

Steve
 
This is probably not news to anyone, but the grind and edge geometry on Buck's model 110 and 112 lend themselves to scary sharpness, even with crappy steel. ;)

I was once hanging around with a couple of guys who were forging their own knives and they were starting to get pretty good. As a demo, they got the de rigeur one-inch hemp rope and a long blade (about 9-10 inches) they'd made. After whacking off a hunk of rope, I asked if I could try too.

But instead of using their really long knife, I pulled out one of the original Bucklites (with the same blade as the model 112) which was (I think) made of 425CM. I'd sharpened it with a DMT diamond rod and then used a worn-out version of the same rod to "steel" it lightly to a nice, grabby edge that would pop arm hair. Anyway, I took a quick swipe at the rope, not expecting much, and was really surprised when I heard that weird "rope being cut" noise.

Then all three of us stood there looking alternately at the hunk of rope on the floor and the dinky li'l stainless blade. They thought it was too short and too light to cut a free-hanging rope. Apparently it wasn't. :D

Granted, hand speed and technique helped quite a bit, but that blade grind and edge geometry are first rate for having the sharpest edge that a given steel/heat treat will produce. Maybe not the best, but definitely very good and easy to maintain with diamond abrasives.
 
My experiences with "cheap" steel are half bearing out what Dan "Master of Convexity, W2, and Videos" said. My pop and I both own generic Swiss Army style pocketknives. They're hair-popping sharp because I was left alone in a room with them, my EdgePro and Sharpmaker. I also have some kitchen knives from Dollar Tree (guess how much they cost!) that have pretty good original edges, but they will not sharpen without a lot of work. The best I could do with one was take it down to 18 degrees per side and add a coarse micro-bevel (120 grit stone) to try to match its initial sharpness and cutting ability.

Tried neo-Luddite power-stropping one last night. After several hundred passes over the .5 CrO micron paper did nothing, I plopped some 90 micron SiC powder on a mousepad and stropped away at both sides to raise a burr and hopefully wear away the original hollowed-out edge. Got halfway there (burrs, but still some of the hollow) and moved to some 5 micron SiC paper (cuts faster than 15 micron SiC on an EdgePro tape blank while leaving a mirrored finish). Went nuts with that puppy until the edges and right above the hollow were super shiny. Raised burrs and deburred them (as far as I can see and as far as can be felt on an edge tester), but the knife still cuts like crap.

Should I continue with the more aggressive stropping until the edges are completely devoid of hollows and then return to the finer abrasive or chalk the results up to dollar-store stainless and move on?
 
Originally posted by thombrogan
...Dan "Master of Convexity, W2, and Videos"...
Click to expand...

:o :o

Originally posted by thombrogan
...neo-Luddite power-stropping...
Click to expand...

:eek:


After raising a burr and then deburring...you're supposed to strop. Not vice versa. If I understood you correctly, that's why you have a crappy edge.

My sharpening process goes through several phases of sharpness. I start out at 120 grit or so with a sharp-enough-to-shave-but-still-coarse edge. I go up the grits until 400. Still quite sharp. Then, I deburr at the buffer. At this point it becomes duller than a doorstop...and all the gnats are ROTFLTAO...then I go to a super fine micron belt and then strop. That gets the gnats running for their unshaven lives...!!!:eek: :eek:

:footinmou
 
Sando - convex + hollow grind

I believe Nathan House does this as well. It's a good grind. Only concern is that over time and with multiple sharpenings, the edge will change shape - might get strange if the final convex bevel is not wide enough. I would think that if it's at least 3/16" there would be no worries.
 
Okay, so I took the set an edge and polish too literally. It already had an edge, so I jumped right into polishing. When that didn't work, I went to the 90 micron SiC powder and raised a burr on both sides. Then went to the 5 micron film.

Tried the buffer and red compound on the Dremel and don't think I did it right. Will go back to the coarse powder on the mousepad soon and start again.

Thanks, Dan.
 
Originally posted by Boink
Shaving sharp is when it removes hair from your arm (or other appendage) - scary sharp is when the hair jumps off your arm in resignation as the blade approaches and prior to contact. Some like scary sharp better.
Click to expand...

This is one definition I am going to add to my lexicon.....Boink has clearly made the distinction 'tween the two degrees of near-zero width. :D
 
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