Reprofiling m390. Can't create a burr

[CaPpedDoG]

I'm still fairly new to sharpening but I've had some pretty good success with many knives now (and felt pretty confident until now ) I'm sharpening with the Work Sharp Precision Adjust.. with the upgrade kit. However, I'm having a hell of a time reprofiling my Koenig Arius to 17 degrees. I cannot for the life of me seem to produce a burr except on the belly. I've tried and tried with no luck and now I'm getting a little concerned about causing some sort of damage on such a beautiful knife (is that possible when reprofiling?) Any tips?

 

[toker]

M390, 20CV and CTS204P barely form a burr, if at all. I personally don't bother trying on any of those steels. I use a Wicked Edge, so I just do about a dozen passes on each side with each grit progression.

 

[CaPpedDoG]

M390, 20CV and CTS204P barely form a burr, if at all. I personally don't bother trying on any of those steels. I use a Wicked Edge, so I just do about a dozen passes on each side with each grit progression.

Appreciate the reply. That's good to know. How come the belly produces a burr no problem though but the rest won't? Also, the belly is already very sharp compared to the rest.

 

[SVTFreak]

Appreciate the reply. That's good to know. How come the belly produces a burr no problem though but the rest won't? Also, the belly is already very sharp compared to the rest.

In the belly, you get more pressure since it’s not contacting the entire stone width, only a small patch. So it cuts faster there and can create a burr a little better. But it’s also why you see so many bad sharpening jobs where the belly is ground out. I, too, have less success on m390 getting a burr. Use a sharpie and finger test and usually get great success without a burr. Sometimes, depending on the treat, I can get one but it’s so just barely there I really have to pay attention feeling for it.

 

[3D Anvil]

I've never not been able to raise a burr with m390. With most knives, regardless of steel, it takes longer towards the heel and tip. One reason is geometry, but it can also be technique. If you're sharpening pass goes in both directions, i.e., starting at the heel, going to the tip, and then going back to the heel, the middle of the blade gets hit more often than the heel and tip.

Let's count, starting from the heel....

Heel (1)
Belly (1)
Tip (1)
Belly (2)
Heel (2)
Belly (3)
Tip (2)
Belly (4)
Heel (3)
Belly (5)
Tip (3)
Belly (6)
Heel (4)
Belly (7)
Tip (4)
Belly (8)
Heel (5)
Belly (9)
Tip (5)
etc.

In other words, if you sharpen in both directions, the belly gets sharpened about twice as much as the heel and tip. The solution is to either sharpen in one direction only, or to consciously do more strokes at the heel and tip.

 

[CaPpedDoG]

Thanks everyone. So because the burr formed on the belly of my blade is so noticable (even though it's m390), does that mean I should continue trying to reach a similar burr along the rest of the edge?

Also, now that the belly has a burr, do I only focus on sharpening the rest of the edge - skipping the belly with each pass?

 

[Twindog]

M390 produces a burr just fine. If you're not producing a burr, you're not reaching the apex, either because your stone angle is too shallow or the edge profile is too obtuse and you're working the edge shoulder.

Use a Sharpie and a loupe to see where the grind marks are hitting.

 

[3D Anvil]

Thanks everyone. So because the burr formed on the belly of my blade is so noticable (even though it's m390), does that mean I should continue trying to reach a similar burr along the rest of the edge?

Also, now that the belly has a burr, do I only focus on sharpening the rest of the edge - skipping the belly with each pass?

I would keep going until you get a full burr on both sides. I would concentrate on the areas that don't have a burr. When you have the full burr, then do another couple passes along the full length to even things out.

 

[CaPpedDoG]

M390 produces a burr just fine. If you're not producing a burr, you're not reaching the apex, either because your stone angle is too shallow or the edge profile is too obtuse and you're working the edge shoulder.

Use a Sharpie and a loupe to see where the grind marks are hitting.

Am I wrong in thinking that I can continue to sharpen at a 17 degree angle with a 220 stone to reach the apex and create a burr? I've tried for a very long time today and totally unable to get a bloody burr. It feels next to impossible.

 

[AntDog]

Am I wrong in thinking that I can continue to sharpen at a 17 degree angle with a 220 stone to reach the apex and create a burr? I've tried for a very long time today and totally unable to get a bloody burr. It feels next to impossible.

Sure you can continue and will eventually get there, but it’ll take forever. If you’re changing the edge angle you’re not sharpening, you’re reprofiling. Do the sharpie trick and see where it’s hitting. Diamonds work quick for what you’re trying to do.

If you want it at 17°, I’d get some diamonds and reprofile the whole edge to that angle. Then just refine it with the stones of your choice.

 

[CaPpedDoG]

Sure you can continue and will eventually get there, but it’ll take forever. If you’re changing the edge angle you’re not sharpening, you’re reprofiling. Do the sharpie trick and see where it’s hitting. Diamonds work quick for what you’re trying to do.

If you want it at 17°, I’d get some diamonds and reprofile the whole edge to that angle. Then just refine it with the stones of your choice.

Sorry, maybe I used the wrong word. I'm using a 220 grit diamond - not stone. I've been going at this blade with the 220 diamond for what seems like forever now trying to reprofile. The belly is no problem whatsoever but the rest just won't get there. I'm getting confused and frustrated with it I've tried the sharpie and see it won't reach the apex...

 

[Twindog]

Here are two possibilities. Where the Sharpie ink is scraped off will tell you a lot.

[Top photo] On the lower side with the burr, the stone is at the apex, creating the burr.

On the upper side, the stone is at a more acute angle than the edge bevel and it is grinding off the shoulder. You won't get a burr here for a while. The red shows where you will see the Sharpie ink being scraped off.

[Below] Here, the stone on one side is at a less acute angle than the edge and is quickly creating a burr and a microbevel.

On the other side, the stone angle is too acute, compared to the edge bevel. No burr.

Again, the red shows where the Sharpie ink will be scraped off.

 

[CaPpedDoG]

Here are two possibilities. Where the Sharpie ink is scraped off will tell you a lot.

[Top photo] On the lower side with the burr, the stone is at the apex, creating the burr.

On the upper side, the stone is at a more acute angle than the edge bevel and it is grinding off the shoulder. You won't get a burr here for a while. The red shows where you will see the Sharpie ink being scraped off.

[Below] Here, the stone on one side is at a less acute angle than the edge and is quickly creating a burr and a microbevel.

On the other side, the stone angle is too acute, compared to the edge bevel. No burr.

Again, the red shows where the Sharpie ink will be scraped off.

Really appreciate that! I attempted to record a video through a loupe. Do you mind taking a look?

0 new items by Brian Speight

photos.app.goo.gl

 

[Twindog]

Really appreciate that! I attempted to record a video through a loupe. Do you mind taking a look?

0 new items by Brian Speight

photos.app.goo.gl

It's difficult to see what is happening because of the video quality. A good loupe would work better.

I've never used the Workshop Precision Adjust sharpener, so I don't know how well that clamp works to keep the blade perfectly perpendicular to the clamp base. Full flat grinds can leave the blade just off center, making it easier to raise a burr on one side than the other.

I'd paint the edge with a Sharpie, but then make just one light pass.

If this is the first time you've sharpened this knife, the factory edge could be quite a bit off in terms of grind angles on each side of the edge -- say 15/20 dps. You should be able to measure those angles with your set up. Look for the angle where the paint is scraped clean with one light pass on the full bevel. That will be the angle on that side of the edge bevel.

Make sure you sharpen all the way out to the tip, but don't let the stone slide off the tip, It looks like you're not getting the tip.

So set up your clamp, making sure the blade positioning is exact and the blade doesn't move with moderate pressure.

Paint the edge.

Use a fine grit stone to make one light pass, than use a good loupe to see where the stone is hitting.

Make a plan from there.