How To Thoughts on sharpening an Elmax chisel grind

[maximus83]

So I got my first @Charlie Mike blade, a chisel grind in Elmax, post with pics, specs, and initial sharpening results is here:
https://bladeforums.com/threads/charlie-mike-elmax-blade.1558117/

A great knife! But wanted to discuss first observations and options for freehand sharpening a chisel grind with Elmax steel. Apologies for the longwinded post, just documenting full process i went through, and raising a few ideas for discussion.

What I did:

• Reprofiled and lowered edge angle to 30 degrees inclusive.
• I had not sharpened a chisel grind with such a high edge angle, and that plus the deep belly made it difficult for me to freehand the edge reprofile and get a clean bevel. Finally in the interest of time, I 'cheated' and used Sharpmaker and my Moldmaster 150 grit Sic stones to complete the reprofile and set a clean 30 degree bevel. Hey don't bust my chops, I'm a weekend sharpener here, I'm not HeavyHanded . To do that, I took a tip from HeavyHanded , laid the blade flat on one stone with the 30 degree setting, then hold that angle, and sharpen the bevel on the other stone. That took a while but accomplished the goal of a clean 30 degree bevel.
• After the edge reprofile, I went thru two sharpening progressions:

1. All SiC. 150 > 240 > 600 (used Sharpmaker with Moldmasters)
2. All diamonds. DMT XC (220) > DMC C (325) (freehand)

• Strop: in both sharpening progressions, I did not strop the edge. But I stropped the flat/unground side by elevating blade just barely and stropping to deburr. Tried 3 different strop options: Spyderco UF ceramic, 10 micron diamond compound on hardwood, or backhoning on DMT C or EF plates. The diamond backhoning deburred the fastest and got best sharpness.

As you'll see in the linked thread, the all SiC sharpening results were surprisingly good, the edge was easily sharp enough for EDU. But when I went to diamonds, it bumped it up another notch entirely, even though I only sharpened on 2 grits, and did nothing to strop or refine the primary edge other than light finishing strokes on the DMT C plate.

Learnings:

• SiC can work well for EDU-quality sharpness on Elmax at HRC 61. But diamonds work noticeably better on Elmax, and get you there faster. As expected.
• I got best results with the 2-grit coarse diamond progression above. I tried using higher DMT grits, all that did was nothing or even degrade the general cutting performance. The coarse results were noticeably best.
• I tried using Spydie UF ceramic to refine: fail! It degraded the edge sharpness, even with super light strokes.
• The importance of stropping the flat side on the chisel grind. I knew this in general, but really observed here how important it was to get this step right. Elmax on this blade can get a very fine wire edge burr, hard to detect, but if you don't get rid of it, it hangs around and really impacts your sharpness.

Questions for follow-up:

• Anyone have tips on how to scrub/shape/profile an edge at such a high sharpening angle, without horking it, when you have a deep belly curve? Man I struggled with that.
• Stropping method I used. Should I do something different? For instance, should I strop the flat side on a higher grit diamond like the DMT EF or even EEF, that won't be so aggressive?

Pics (most are in thread, but a few here for convenience):

New knife:

Horizontal push-cut on Rizla green after sharpening on DMT C:

Close-ups of the finished edge. Not bad finish for 325 mesh and no strop.

 

[HeavyHanded]

I have more tips maybe but short of time right now.

In my experience these chisel grinds are very much like wide bevel Scandi with a pronounced belly. Limit how much you scrub through the belly area. It is OK for stock removal, but once you get close, switch to a sweep at least through the belly. It is otherwise not possible to get a clean cosmetic surface on broad bevel + pronounced belly. It can be a sweep back and forth, but it should encompass the start of the belly through to the tip or just shy of the tip. Stop often to inspect and make sure the ares to either side of the sweep zone are blending in well.

It will be tough enough even with very good technique. As always, avoid learning new skills on expensive knives when possible - even if it means doing a mockup from flat stock or similar. The curved half of a bypass shear is a good low budget stand in for a chisel grind with pronounced belly. I'm not sure if they are ground the same side though - has been a few since I sharpened one.

 

[maximus83]

It is otherwise not possible to get a clean cosmetic surface on broad bevel + pronounced belly. [snip]
It will be tough enough even with very good technique. As always, avoid learning new skills on expensive knives when possible - even if it means doing a mockup from flat stock or similar.

Whew, that kinda makes me feel better and confirms that these things are a different animal to sharpen freehand. That issue of it being an expensive-to-me custom knife, plus just the time/frustration I was having trying to learn to reprofile that edge freehand, was what convinced me to go to the Sharpmaker with SiC stones, and doing that, it bailed me out and got a pretty good profile with a lowered edge angle. Once that was done, freehand sharpening the profiled edge on my diamond plates was straightforward and I could get a great edge.

In addition to the whole how-to-reprofile-a-chisel-grind issue, I'm also interested to hear experienced sharpeners' thoughts on how you strop them. What I did stropping the flat side seemed to work, but I wonder if there's more I could do there. Once I got the sharpness up to a level I normally expect and a good toothy edge, I was halfway leery of further messing with it on strops, I figured I was as likely to degrade the sharpness as improve it, at that point.

 

[maximus83]

Did some more work on this one all freehand this time.

• Reset the bevel at same 30 degree angle using DMT XC (I didn't have to scrub since the angle was already there, so this made the freehand bevel reset easier than before). Then apexed on the XC until it would clean-slice newsprint again.
• Refined on the DMT XC.
• Deburred the flat side on the DMT EF. This surprisingly took nearly 20 light strokes to remove the thin but hard burr I had worked up from apexing.
• Stropped the flat side, and the edge this time, about 10 laps each on my wood block with CBN.

The knife would perform all the same sharpness tests as above, but with noticeably less friction, and less sound, when making diagonal slices thru newsprint. Also, would push-cut all the way through phonebook pages to the bottom--couldn't do that before. It push-cut a piece of Rizla green without needing a starter cut.

What I changed was to pay much more attention to deburring, and then added stropping on both sides of the blade. The outcome was quite a bit better.