Best way to hone a convex edge.

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Mmm390

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Jan 26, 2019
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hello.

What is the best way to hone and maintain a 15-17 degree double bevel convex edge with a 30 degree inclusive micro bevel?
I'm currently using a cheap stropping steel and I also strop it at 15-17 degrees but I can't seem to get consistent results.
Maybe i just need more practice or a better steel.
Are there any better methods/tools?
 
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Diamond lapping films pasted to balsa with some give, and a sharpie to match the bevels. Jende has 2x6 and 3x8 lapping films from 80 micron to 0.5 micron (~180 grit to ~30,000 grit).
 
If you're trying to maintain that exact edge geometry (double bevels + microbevel), it's going to be complicated to do it accurately, at least without a guided setup. Otherwise, if done freehand, you'll more likely alter it one way or another (by constantly changing the held angle, rounding off the edge, etc). Trying to 'convex' the edge, while also trying to maintain such exact 'bevelled' geometry, will be mutually exclusive.

Ordinarily, a pure convex is easy to maintain, especially edge-trailing on sandpaper or on an aggressive strop. But convexed edges aren't normally 'bevelled', as described. Putting it another way, true convexes don't actually have 'bevels' at all. It's contradictory, as 'bevels' are flat-surfaced by definition, and 'convex' is curved outwardly, by definition. Convexed blades sometimes do have factory-applied microbevels added to the edge, after the fact. In maintaining it, unless you completely regrind a fresh, crisp microbevel each time you touch up, you'll more likely round it over or change it, one way or another.

Based on how you describe your maintenance scheme ('stropping steel' + stropping somewhere between 15-17°), I'd guess you're probably rounding off the edge and/or microbevel. Hence the inconsistency in results.
 
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One pass per side on a 1"x42" 400 grit slack belt and polish on a 1x42 leather slack belt with compound. Convex edges are made with slack belts, and they don't have bevels.
 
Yes^. If you don't have this equipment you can do it on a stone. Start it on a 1-200 grit with a V grind and get the edge set. Then as you
work it finer on the next stone just blend in the shoulder of the edge bevel. DM
 
I don't belong in this discussion but I'm always learning stuff . . . sometimes in spite of myself.
Why do you want a convex edge ?
I mean you personally as in what use will you be putting it to ? (not that there isn't reasons to use convexed knives)

Is my math wrong when I look at 17° per side x 2 could possibly at the widest = 34°
and so
it would be impossible to put on a secondary bevel at 15° even if the original bevel was 15° x 2 = 30° original edge geometry.

PS : I'm surprised I didn't hear a call for a mouse pad with sand paper.
 
Mmm390 said:
I'm currently using a cheap stropping steel and I also strop it at 15-17 degrees but I can't seem to get consistent results.
Maybe i just need more practice or a better steel.
Are there any better methods/tools?
Click to expand...

Some times the edge is too dull or damaged to sharpen the edge with just a steel. Some more coarse abrasive on a mouse pad or stone or sanding belt is going to be required to get to where you can use the steel again.
 
Wowbagger said:
(...)
Is my math wrong when I look at 17° per side x 2 could possibly at the widest = 34°
and so
it would be impossible to put on a secondary bevel at 15° even if the original bevel was 15° x 2 = 30° original edge geometry.

PS : I'm surprised I didn't hear a call for a mouse pad with sand paper.
Click to expand...

:thumbsup: Good catch. I'm slapping my forehead at not seeing that. That could explain the results, if the 'microbevel' is being attempted at an angle narrower than the primary bevel angle. Edge never gets touched...

( I actually mentioned sandpaper... Though I'd ditch the mouse pad in favor of something firmer. ;) )
 
Ah I see.

So if my micro bevel is 30degrees inclusive.
Should I also hone/strop it on a steel at 15 degrees per side?
Any wider and I'd just be dulling it...
Correct?
 
Mmm390 said:
Ah I see.

So if my micro bevel is 30degrees inclusive.
Should I also hone/strop it on a steel at 15 degrees per side?
Any wider and I'd just be dulling it...
Correct?
Click to expand...

Make sure the edge is fully apexed, above all else. Nothing else matters until that's done.

If the primary bevel above the microbevel is actually something wider than 15-17° per side, i.e., more than 30° inclusive, then the edge can't possibly be apexed yet, as your attempts at the microbevel will only be touching the shoulders of it, and not the edge itself. Mark the edge with a Sharpie, so you can see where the ink comes off (at the edge, or above it) as you hone. If the ink is only being removed above the edge, that would confirm you're not working at a wide-enough sharpening angle and the edge isn't being touched.

Form a burr from each side, one side at a time, using a stone. The burr should be the full length of the cutting edge, as formed from each side. The burr will verify the edge is fully apexed. Then use either the stone or your strop to reduce or eliminate the burr and enhance sharpness. Check for sharpness frequently (cutting paper, etc) as you're doing this, so you can be sure you're not rounding or blunting the edge in doing so.

For the time being, I'd avoid using the steel to hone it. That won't likely do anything for you until the edge is fully apexed anyway. If it's not apexed, the steel will just burnish it or round it off and blunt it further.
 
Ok.

The primary bevel should also be 30 degrees inclusive.
That's what I had it dialed in it when I reprofiled it...
But I understand things can be a little off when it's not a guided system.
That's why I said 15-17 degrees.

I do have a strop that I havnt had time to practice on.
It may be time for some more trial and error

I may need to get a jewelers loop as well.
Any idea what magnification is optimal?
 
For a loupe, anything up around 3X-10X and well-lighted has served well for me. Good lighting makes a big difference, whether it's coming from the loupe itself or from an external source. Any magnification higher than that, sometimes the working distance and/or lighting issues become a problem.
 
I've found that sharpening freehand on bench stones works well with convex edges -- just stroke backwards (trailing edge). If you need to remove a lot of metal to reprofile, start with a fine file. I did this with my SRK, which had a very obtuse edge when new, and ended up with a very nice convex edge that cuts a whole lot better.
 
Be sure to see the "Sticky" on the Mantenance, Tinkering and Embelishment home page about Microbevels here at this LINK>>>>>

This is one hell of an obtuse micro bevel in the diagram at this link but it is a clear illustration of what a micro bevel is.
Follow this LINK>>>>
PS: page down at that second link.
 
Mmm390 said:
hello.

What is the best way to hone and maintain a 15-17 degree double bevel convex edge with a 30 degree inclusive micro bevel?
I'm currently using a cheap stropping steel and I also strop it at 15-17 degrees but I can't seem to get consistent results.
Maybe i just need more practice or a better steel.
Are there any better methods/tools?
Click to expand...
Hi,

Do you own any sharpening stones? Perhaps a dollar tree stone?

This would be baby steps on a stone,
very natural,
its what I did before learning to hold an angle
(using a cardboard triangle, now popsicle stick triangle)
Not enough convex with stone on table?
Hold stone carefully in hand for extra convex :) (protect fingers , diy stoneholder)
A problem with this approach is burrs can come faster than you can maintain behind the apex
But with practice you can move on to advanced version below

hard.gif

convexingjig-lg.gif



This would be advanced convex sharpening on a stone,
its what I do now that I've practiced :)
Paint the edge
Work low angle, medium angle, and target angle (15dps)
Maintaining relative angles works well enough,
but if you want more exact cross section you gotta measure
Sharpening a convex recurved blade on a bench stone : Forester
 
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I have a heavy rubber strike pad. Denser and less give than the mouse pad.

I also use a stone and ceramic sticks to maintain convex edges.
 
I use a lozenge shaped closed cell foam pad designed for padding on the inside of whitewater kayaks and diminishing grits of sand paper. Pad is firmer than a mouse pad.--KV
 
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