Bevel Height: What to Know

[bratch]

I was sharpening a Wheeler 3 finger that had gotten dull using the Work Sharp Precision and noticed that the height of the bevel it put on was several times larger than the original edge.

What is the functional difference in the very small bevel that was originally on there and the new wider bevel I put on? Any tips or tricks for maintaining the factory edge height if it is a better edge?

It is extremely sharp now so I’m happy with that outcome.

Here is the resharpened knife on the left and a different Wheeler with the original thin bevel on the right.

 

[JohnKSa]

The height of the bevel is a function of two things.

• The sharpening angle. The more acute the sharpening angle (the smaller the angle) the higher the bevel will be, all else being equal.
• The thickness of the blade right behind the edge. The thicker the blade is at the edge, the higher the bevel will be for a given sharpening angle.

What you are seeing is that the sharpening angle you used when you sharpened the knives is more acute than the original factory edge and that made the bevel reach higher on the blade.

• The more acute the sharpening angle, the sharper the knife will be (the better it will slice things), assuming that the sharpening process was performed properly.
• The more acute the sharpening angle, the more fragile the edge is. The blade will be thinner right behind the actual edge and that means it isn't as strong. If the knife is subjected to hard use, the edge will roll or chip more easily with an acute sharpening angle.
• The more acute the sharpening angle, the better the knife will hold an edge--ASSUMING that it is not stressed beyond what the combination of the knife steel, the hardening process and the edge geometry can handle. Said another way, a knife that is subject to primarily abrasive wear (slicing things that gradually wear away the edge), as opposed to wear that is likely to roll or chip the edge, will hold a workable edge longer if it is sharpened to a more acute angle.

There are general rules of thumb for sharpening angles based on the intended use of the knife. People like kitchen knives sharpened to a very acute edge because they are used primarily for cutting relatively soft things, not for chopping or cutting through hard materials. We have cleavers for chopping. Knives intended for chopping or for cutting through hard materials may benefit from a less acute edge since they are subjected to the kind of use that may chip or roll an edge.

If you find that your edge starts chipping or rolling from the type of use you put on the knife, then maybe, next time, sharpen with a less acute (bigger) angle which will make the knife less good at slicing but more suitable for the use you are putting on it.

If you find that the edge is holding up ok--no rolling or chipping--then keep sharpening it with the angle you are using.

 

[nettlle]

JohnKsa pretty much has this covered. Controlling the blade angle and the burr is the majority of the battle.

 

[bratch]

Thanks @JohnKSa I’m not sure why I didn’t think of the angle connection.

That makes sense now. I sharpened the left to 15*, being a smaller knife with no guard I thought it would be better with a more acute slicing edge as I don’t see myself using it for heavy cuts.

 

[Mk-211]

What's the factory angle for the one on the right? 20-21°

 

[JohnKSa]

Every time I've seen video of the sharpening phase from a production knife company, it's someone free-handing it on some kind of power sharpener--usually a belt or wheel grinder. I've seen even pretty expensive production knives where the angle on one side is an obvious mismatch to the other or where you can see that the angle is not consistent over the entire blade, even on the same side.

All that to say: The factory angle is probably not really set to a number as much as it is "eye-balled" by whoever's doing the sharpening that day.

 

[bratch]

What's the factory angle for the one on the right? 20-21°

Most of the edge was about 20*, towards the tip was a little higher, at least according to my Sharpie and Work Sharp.