Wide bevels

[joesrx]

I recently sharpened a 940 and the bevels at the curve got larger then the flat of the blade. It was with a guided system set at 20%. Is this the nature of the beast with those thick tips or can I improve my technique? Any advice is appreciated.

 

[Crag the Brewer]

Pics?

 

[joesrx]

 

[David Mary]

It's just a function of geometry. They ground the blade cross section such that it is thinner at the heel and thicker at the tip. Your options are fairly limited to either wider bevel at the thicker cross sectional portion of the blade, or more obtuse angle if you want to keep bevel width the same, and in either case there is no simple way to calculate it and you're best to just do it freehand.

 

[David Mary]

That is, of course, assuming you don't want to regrind the blade geometry itself, but only the edge.

 

[joesrx]

As long as I’m not screwing it up, I can live with it! Thanks for the explanation.

 

[David Mary]

You're welcome.

 

[Daniel]

It is due to the position of the blade in the clamp. It is not necessary to have a wide tip and belly bevel.

Try using a sharpie on the edge and check different positions to find out where it is hitting the edge. You will find the reason through a little trial and error where it rubs the sharpie off.

 

[Blade Lab]

It looks like you had the knife clamped diagonally, with the handle farther away from you than the tip? I say that because the bevel is smallest at the heel and seems to widen out continuously.

 

[David Mary]

Also a possibility. I don't use this style of sharpener, so if these folks do, then I'd defer to their replies.

 

[Daniel]

Here is a clamping example:

 

[eveled]

You need to get calipers to check the thickness at various points to see if that is the issue.

And/or check to see if your edge angle stays the same.

I know with a Lansky the further you get from the clamp the angle changes. Did you sharpen it clamped at the Ricasso end?

Something wonky happened at the heel for sure.

 

[joesrx]

Actually the heel wasn’t sharpened due to the thumb studs getting in the way. I did not remove them and they were in the way. I will redo today.

 

[joesrx]

Here is a clamping example:

View attachment 2424207

Thanks, this is helpful!

 

[joesrx]

Is there a fix or wait till the blade is sharpened down and it will correct itself?

 

[TheOne45]

I use angle cube to measure the angle at the heel and at the tip before I start sharpening. Then I try to reposition the blade in clamps till I get about the same angle at heel and tip.
For example; if I sharpen the blade at 17 degrees I get readings on my angle cube (speaking from memory for one of my EDC knives):
heel: 16.6 degrees
middle of the blade: 17 degrees
tip: 16.6 degrees
If the bevel after sharpening is larger for example at the tip, this means the blade it thicker behind the edge at this side.
In that case I try to reposition the knife in clamps next time to compensate this thickness difference so I get about the same width of the edge.

Is there a fix or wait till the blade is sharpened down and it will correct itself?

I don't think the blade will correct itself. If primary bevel is grinded so the blade is thicker behind the edge on one side (at the heel or at the tip) it can't correct itself.
You would have to repair (regrind) the primary bevel to even out the thickness behind the edge.

 

[joesrx]

 

[joesrx]

So here is the knife after playing around (ocd is a b-tch). So for longer and thicker blades I will need to move the knife during sharpening. By the way, I have worked with easier steels then s90v. The bevel chart will definitely help. Thank you all for your help!

 

[Cementite]

It is due to the position of the blade in the clamp.

^ This.

If you clamp the knife in the jig closer to the tip of the knife, you won't get as long a bevel at the tip.

Think about it. Imagine if your knife had a 36" blade. If you clamped it in the same position you have it in the photo above (assuming you had 36" long rods on the stones for your jig), the bevel at the tip of the 36" blade would be super long, because the angle between the stone and the edge at the tip would be much more acute than the angle between the stone and the edge closer to the clamp.

This might help you visualize what's happening:

https://www.carbidedepot.com/formulas-trigright.asp

If you want a shallower bevel at the tip, you need to clamp the knife in the jig closer to the tip. Consider sharpening the back of the blade, then repositioning it in the jig clamp before sharpening the tip of the blade. Then blend your edges together.

Without a more sophisticated jig, there's no easy or pretty way to do this...

 

[Crag the Brewer]

Actually the heel wasn’t sharpened due to the thumb studs getting in the way. I did not remove them and they were in the way. I will redo today.

That's what I was wondering/thinking.
Making your edge more obtuse.