Holy Big Burrs Batman!

[HumbleHomeCook]

So I had a new-to-me experience today.

Subject knife is a Hatsukokoro AS Bunka. Hatsukokoro Kurosagi 180mm AS Bunka

Just got it yesterday. The OOTB edge was okay but definitely up to standard and the last ~1/2" or so of the heel was actually pretty dull. It was a near zero grind and I just basically didn't pay a lot of attention and chalked it up to a lower-end knife grind.

I put it on my SG500 first and...

It burred up really quickly and obviously significantly.

I'm not sure I've ever encountered that kind of rapid and huge burr formation on even the softest knives I've sharpened. Happened on both sides to start. I kinda do a loose Peter Nowlan style of sharpening with decreasing pressure but when I realized the kind of burrs I was getting, I did a couple additional higher pressure passes on each side than I normally do. Then it seemed to clean up and started to "normalize". I did a LOT of light edge trailing, de-burring strokes and then stropped on suede with CrO, cardboard, and hell, even my flannel PJ pants! I pretty much never do that between stones but I want that nasty ass burr gone!

I went to my SG2k and everything felt normal and as expected. Again, more-than-normal de-burring strokes on the stone and then on some cardboard.

Decided to go to my SG4k and really just did feather light passes and de-burring.

When I was done it was singing through paper towel. I was a little hyper sensitive but I believe the steel didn't feel bad on the stones.

I know bad heat treat might be tossed out as a potential culprit and maybe it is, especially at this price point, but I feel like that's a too frequent go-to. And given that it felt like things sorted out, I'm inclined to think it was just a crappy original job and likely left some weak steel hanging on at the very edge.

I know I need to use it and see how it holds up but what do you guys think?

 

[Rangen]

I know bad heat treat might be tossed out as a potential culprit and maybe it is, especially at this price point, but I feel like that's a too frequent go-to. And given that it felt like things sorted out, I'm inclined to think it was just a crappy original job and likely left some weak steel hanging on at the very edge.

I know I need to use it see how it holds up but what do you guys think?

Bad heat treat is always a possibility, but my guess is that either you are exactly right, or the edge was ground on a powered tool, ruining the heat treat for the very edge, leaving plenty of good steel to find once you get past the bad.

 

[M1k3]

Sounds like a zero edge was created. And then the profile slightly tweaked afterwards?

 

[HumbleHomeCook]

Sounds like a zero edge was created. And then the profile slightly tweaked afterwards?

Yeah, no doubt but I've done that on other knives and not had that kind of burr shedding. My "natural" freehand runs around 15dps so nothing extreme.

Could still be it though. Maybe a combination effect.

 

[M1k3]

Yeah, no doubt but I've done that on other knives and not had that kind of burr shedding. My "natural" freehand runs around 15dps so nothing extreme.

Could still be it though. Maybe a combination effect.

The quickness raising a burr says to me zero edge. The few dull parts tell me either those parts didn't get to zero, or something ground the edge slightly.

 

[HumbleHomeCook]

The quickness raising a burr says to me zero edge. The few dull parts tell me either those parts didn't get to zero, or something ground the edge slightly.

Certainly makes sense. Like I said, I do think it was mostly zero edge to start. Should've studied it a bit more before jumping I guess.

 

[M1k3]

Certainly makes sense. Like I said, I do think it was mostly zero edge to start. Should've studied it a bit more before jumping I guess.

Nah, jump in head first! Ask questions later!

 

[HumbleHomeCook]

Nah, jump in head first! Ask questions later!

My man.

 

[Matt Jacobs]

I had this happen once on a Shiro Kamo R2 damascus gyuto. Even more pronounced than the one you have. It shocked me as well I thought my beard hair was falling out. It only happened on the initial sharpening and then never again. Maybe the very edge was overheated when the factory sharpened?

 

[gc0220]

I got something for you. Just the thing for this thread. Check this out. Happened last night with some hard AS I was hitting on the shapton pros. 2k and 12k. Then I took it diamond on wood at half a micron for some refining, then tenth of a micro loaded leather for the finish. Not that any of that is relevant, this burr was created on a 2k shapton pro and removed on stone.


If you dont mind a hard ass stone, these shapton pros are really fantastic and convenient for sharpening carbon steels, and I'm talking about at the higher grits like that 12k. The trick to getting a burr like this in so far as there is one is just making sure you stones are flat for starters. I use a 400 grit atoma plate. DMT course (325) is fine, however just fyi the course plate is the only product DMT sells that I'd recommend anyone purchase. Unless of course you want something that has a crazy high stock removal rate, then you can try their quote unquote "higher grit" products, like their 1200 grit and above, up to "8k" they claim. Sometimes I'll use one of their "600 grit" "hardcoat" smaller plates as like a fixer stone and to generate slurry. It works very well for this purpose and once it's broken in I've never had any kind of grit contamination occur.

 

[gc0220]

Sidenote for OP, "burned edges" are in my opinion a very real thing. It can be pretty frustrating. No doubt bad heat treats or entirely wrecked tempur on blades is a real thing too. \

 

[HumbleHomeCook]

Sidenote for OP, "burned edges" are in my opinion a very real thing. It can be pretty frustrating. No doubt bad heat treats or entirely wrecked tempur on blades is a real thing too. \

Burned edges and bad heat treat are indeed real and I don't argue against either. However, they get tossed out as the cause for all manner of things. This is especially prevalent in the EDC world.

I suspect this knife was sharpened on an actively cooled wheel so I doubt it was a burnt edge and since it seems to have settled down it's probably, possibly, but probably not a bad heat treat.

 

[ModRQC]

If the zero grind was inconsistent probably you did best to sharpen with an (consistent) angle. I mean I'd be less wary to then convert my own sure source work into a zero grind again than working on a wonky one, if that's just that - and if that makes sense?

 

[cotedupy]

So I had a new-to-me experience today.

Subject knife is a Hatsukokoro AS Bunka. Hatsukokoro Kurosagi 180mm AS Bunka

Just got it yesterday. The OOTB edge was okay but definitely up to standard and the last ~1/2" or so of the heel was actually pretty dull. It was a near zero grind and I just basically didn't pay a lot of attention and chalked it up to a lower-end knife grind.

I put it on my SG500 first and...

It burred up really quickly and obviously significantly.

I'm not sure I've ever encountered that kind of rapid and huge burr formation on even the softest knives I've sharpened. Happened on both sides to start. I kinda do a loose Peter Nowlan style of sharpening with decreasing pressure but when I realized the kind of burrs I was getting, I did a couple additional higher pressure passes on each side than I normally do. Then it seemed to clean up and started to "normalize". I did a LOT of light edge trailing, de-burring strokes and then stropped on suede with CrO, cardboard, and hell, even my flannel PJ pants! I pretty much never do that between stones but I want that nasty ass burr gone!

I went to my SG2k and everything felt normal and as expected. Again, more-than-normal de-burring strokes on the stone and then on some cardboard.

Decided to go to my SG4k and really just did feather light passes and de-burring.

When I was done it was singing through paper towel. I was a little hyper sensitive but I believe the steel didn't feel bad on the stones.

I know bad heat treat might be tossed out as a potential culprit and maybe it is, especially at this price point, but I feel like that's a too frequent go-to. And given that it felt like things sorted out, I'm inclined to think it was just a crappy original job and likely left some weak steel hanging on at the very edge.

I know I need to use it and see how it holds up but what do you guys think?

I'd be fairly confident this is because of the grind rather than the HT. When I've sharpened knives where the HT has been f-ed (I believe), the burrs don't look like that, it's more like tinfoil, and quite clingy - they don't snap off nice and cleanly.

(Might be wrong, but that'd be my guess fwiw).

 

[HumbleHomeCook]

I'd be fairly confident this is because of the grind rather than the HT. When I've sharpened knives where the HT has been f-ed (I believe), the burrs don't look like that, it's more like tinfoil, and quite clingy - they don't snap off nice and cleanly.

(Might be wrong, but that'd be my guess fwiw).

Your input is always valuable my friend.

They for sure were just shedding right off.

 

[gc0220]

what do you guys think would cause the burr i got, that giant long wire was on the stone. I picked it up for the photo op. Came off super blue. is this indicative of an issue with the steel?

 

[mengwong]

Old thread but I want to contribute another hypothesis.

Maybe the burr isn’t burnt but burnished.

When I’ve encountered OOTB burrs like this I’ve asked myself “is this, like, a lacquer on the blade? But surely a lacquer wouldn’t go like that…”

If the edge were factory finished on paper or leather or felt, maybe the soft matrix of the steel is getting wiped along to form a stropped and shapely but softish apex. And against a hard stone, that apex comes unglued all at once.

2¢ jet-lagged.

 

[Choppin]

I also believe the zero grind / thin edge was the cause. happened to me before when sharpening a knife after thinning and making it too thin at the tip. I was using the same stone, SG500. the edge was shedding big burrs like that.

I continued on the SG500 but with low pressure and made sure to deburr well (alternating edge leading strokes).

with edges like that (zero grind and/or nail-flexing-BTE) it's best to start with the SG2k and light pressure. shouldn't take much to create a burr.

 

[daveb]

trailing, de-burring strokes

Others have spoke to possibilities of quick, fat, burr. But that there is one of those oxymoron things.