Sharpening question: What am I doing wrong?

[Jason White]

I ground a new primary bevel on this blade (see photo) using my Veritas MK II honing guide. It's nice and straight, so no issues there.

But... then I ground a secondary bevel using the same honing guide, but a different stone. I made sure the stone was flat. But, as you can see, something is off. The middle of the micro-bevel is deeper than it is at the ends. It's a bevel-up blade made of A2 steel and it's about 3/16" thick. I'm using the straight wheel on the honing guide (not the rounded one made for honing cambers).

Any idea what I'm doing wrong here?

blade.jpg

[Michael Bulatowicz]

I ground a new primary bevel on this blade (see photo) using my Veritas MK II honing guide. It's nice and straight, so no issues there.

But... then I ground a secondary bevel using the same honing guide, but a different stone. I made sure the stone was flat. But, as you can see, something is off. The middle of the micro-bevel is deeper than it is at the ends. It's a bevel-up blade made of A2 steel and it's about 3/16" thick. I'm using the straight wheel on the honing guide (not the rounded one made for honing cambers).

Any idea what I'm doing wrong here?

blade.jpg

Maybe it's a trick of the camera, but your primary bevel looks a bit curved at the heel, more so on the left side of the image than the right. Reasons for this could include a dished first stone or rocking the blade back and forth a bit while sharpening (i.e. alternating applying more pressure on one side and then the other).

If it's an optical illusion and the primary bevel is flat, this would suggest that the second stone is high in the middle compared to the first stone, whether that's a slightly dished first stone, a slightly humped second stone, or some combination thereof.

If the stones are indeed flat or at least matching each other in profile, unintentional rocking seems likely.

How are you evaluating the flatness of your primary bevel and that of your stones?

[Jason White]

They are new ceramic stones and, clearly, they need some additional flattening. Thanks for the input.

[Stephen Prunier]

When I add the secondary bevel, I use 5 degrees more. For my No62, I use 30 primary, and 35 secondary. I also apply extra pressure to the edges to prevent the corners from digging into the wood. To make sure the stones are flat, make some markes on the stone and when there gone or the stone is sticking to what is being used, you know it's dead flat. Sharpening takes time and practice. But it can also be a great way to meditate!

[Reed Gray]

Don't know why you got different results, other than the second stone may not be as flat as you think. I have the DMT lapping plates, and they are dead flat, and will never need to be flattened.

robo hippy

[Eric Rathhaus]

Hi Jason - to really isolate what's going wrong, perhaps you should break down your process, step-by-step for us.

But I recommend you use the blade to find out if something is really wrong first. From my own experience, focusing too much on how the blade appears in order to determine sharpness can be a rabbit hole that's hard to climb out off. Run some test passes. If it cuts well enough to work, it's sharp. Now you have a working reference for sharp. After that you can look at the "sharp" blade and assign a visual reference that is more utile. The more you do it, the more nuanced your references become in relation to the use case, scrub plane plane or smoothing plane, e.g., and the wood, type and grain. The process of developing a feel for a sharp blade on wood will teach you many things and align your pov to the craft and not some abstract definition. Eventually you will find that your blades weren't "sharp" at first. That's okay. The woodworking god/s won't punish you.

[Patrick Baney]

Like others have said, it could be a number of things. But I suggest starting with the flatness of your stone. It's most likely convex (bellied). A convex stone is a sneaky problem and, for me, the source of it is the ruler trick. It's a sneaky problem because it can be difficult to spot, and more difficult to correct. Drawing a grid on your stone and assuming the stone is flat once it's remove is somewhat of a fallacy. If your stone is bellied it can be difficult to apply pressure evenly with your flattening stone to remove the belly, but the grid will be removed. Ever try to flatten a bellied chisel or plane iron? Set a 6 inch rule on edge across the width of the stone and see if it rotates easily.

[James Pallas]

It’s hard to guess because of cameras. I see you have rounded corners. Don’t know how you achieved that. The arc of the secondary looks very even and seems to hit at both edges, that’s good. If the cutting edge is straight or has the camber you want you should be good to go. A honing guide is still operated by the “hands of man”. It is not a precision grinding machine with the iron fixtured in place. A few thou could be expected. If it cuts well it’s good.
Jim