Procedure to fix chips in my Contego?

O

Omega Leather Works

Joined
Jun 13, 2007
Messages
7,743
I absolutely adore my 810. As you can probably tell, I use the thing every day. I don't baby it.

A while back I made the mistake of lending it to a coworker and he snapped the very tip off. I have it sharpened at about 25° inclusive. The knife is still very sharp but the chips are bugging me enough to address them. I don't know how they happened, I haven't paid close attention. I just strop and go most of the time.

nhbnsb2.jpg


I was thinking about running the entire edge 90° against my Norton SiC stone to remove the chips, then use the EP to restore the edge back to its initial angle. Does that sound like a plan, or would you recommend a different procedure?

Thanks guys.
 
Me? I'd just match the bevel and work the entire bevel on the EP to blend everything smoothly until the chips are removed, then re-sharpen as normal. Looks like a serious user there! The 810s are great working knives. :)

Or, perhaps, given that stropping is your preferred method of keeping up your edge, consider converting it over to a convex? Definitely more chip-resistant, anyway, and a quick belt-sharpen would take those chips out in seconds! :)
 
Omega Leather Works said:
I was thinking about running the entire edge 90° against my Norton SiC stone to remove the chips, then use the EP to restore the edge back to its initial angle. Does that sound like a plan, or would you recommend a different procedure?

Thanks guys.
Click to expand...

That is exactly what I would do =) And this is why...

1. Stropping is stressing the very apex of the edge, and bending it back and forth (on a micron level) and is weakening your edge over time - so edge retention will become lower and lower with each stropping session. Doing what you are proposing will "destress" the edge.
2. This will ensure that you are removing the damage in the most efficient method possible while not removing too much metal. If you grind 90* into the edge then you are grinding away metal until you just barely get to the bottom of the chips. This gives you a fresh 'flat' to apex, and once you do, immediately, you know that you have a perfect apex to work with.
3. it just seems to work faster (if doing it all by hand), but as dan points out above, a belt sander would be fastest!

hope this helps =)
 
Interesting. I do use my belt grinder for sharpening large knives and axes, but I like the EP on the smaller (bladed), and more acute bevels.

I've never heard of the concept of stropping damaging an apex. I maintain my wood carving and leatherwork knives by stropping almost exclusively, but they pretty much all have a convex edge.
 
Anthony, your fixing plan is good to restore the look but the usage damages pattern telling you - same old micro chips will happen again. On the flat part of the edge, pressure is more distributed while pressure belly (tip to flat part) is much higher because smaller contact area. Says if those microchips (not the biggest one) is 0.5mm deep, your angle is 12.5dps, hence thickness at 0.5mm is around 0.17mm (0.0067"). I would increase the belly bevel angle to around 17.5dps, which thickness at 0.5mm be 0.24mm (0.0094"), translate to 38% increased in cross sectional area.

For your usage scenario. You can increase cutting performance by thin out your blade, as long as thickness behind the edge is greater than 0.26mm (0.01"). A sharp & stable 17.5dps & 0.01" thick will perform great. For light duty, 14dps is the low stable bevel for steels with 2-4um carbide size. These carbides give wear resistant and edge fracture liability at the same time.

edit: LOL about strop edge floppiness. Could happen if steels is ductile/soft or thin+damaged. Edge rounding and or wire-edge/burring is more likely than flipping around:p
 
bluntcut said:
edit: LOL about strop edge floppiness. Could happen if steels is ductile/soft or thin+damaged. Edge rounding and or wire-edge/burring is more likely than flipping around:p
Click to expand...

Could be, but I am referring to stropping in general leading to loss of edge retention. For example, in Todd's research he has found that the strop material itself has a huge roll in whether a burr is formed or if it is cleanly apexed. The below image was taken after the razor was honed on a Shapton 8k and then taken to 10 laps on 0.25 micron mono-diamond on hanging latigo strop.

8k_plus_p25diamond_10laps_02.jpg


Whereas before it would look like this:

sh8k_e_01.jpg


Then you have other research by the likes of Cliff Stamp which shows that repeated stropping/steeling leads to lower edge retention (see here and here<under the 'sharpening' section>, and also this video). Also it makes sense to me from everything I have read, if you bend metal back and forth then what happens, it will weaken and eventually break.

So just wanted to point out that what I said above was not without merit, and strops can be used to maintain your edge just fine just as long as you understand what is happening and use that knowledge to advance your technique (i.e. not over stropping, rounding the apex, to remove burrs, etc. ) ;)
 
Josh, 1st pic is a wire-edge/burr (i.e. thin & damaged). Strop with abrasive is just a very soft stone (flex degrees depend on substrate stiffness). And there is steeling (with smooth rod) - now we are talking about plastic flow + flipping + fracturing depend on steel properties.

Cliff is very smart, coupled with super duper passionate about cutting implement related matters... He earned my respect. As for his stropping & edge stress/de-stress assertions, I question that grossly generalization based on a subset(minor not major) of the whole range of sharpening (manual & power). Workable steel edge properties covers a wide range of behavior when interact with abrasives + forces. I see that range spanning as vast as from gum to glass. Nowaday, steels ht for high strength (says 60+rc) and many are high alloy. They are less ductile, so most likely fracture when encounter force exceed yield strength or can 'set' one/twice time past elastic region. As you can see why, I have difficult time seeing how undamaged/good steel can flop around.

I don't totally disagree, I just object to generalization on something of whence the majority of users are experiencing otherwise. I pretty much read everything Cliff posted (on his site & Spyderco). His stuff usually very thoughtful & logical and convincing too but me trust I - hahahahaha. I got myself into metallurgy (wanna be) because issues like these, now I feel like I know even less... well, didn't stop me from yakking up a storm eh!
 
Thanks BC, I always look forward to your replies. Always well thought out and backed by math/science/hand waving. ;)

I used to sharpen like a madman. Each blade on a slipjoint had considerations for media cut as well as steel type and hrc. I just don't have time for super polished bevels and hht's anymore. :o I think I may just increase the overall angle to around 28-30° or maybe a microbevel. I definitely don't want a noticeable reduction in slice-ability as this is my favorite attribute. I suppose I could just be more careful when cutting steaks and straps. ;)
 
bluntcut said:
Josh, 1st pic is a wire-edge/burr (i.e. thin & damaged). Strop with abrasive is just a very soft stone (flex degrees depend on substrate stiffness). And there is steeling (with smooth rod) - now we are talking about plastic flow + flipping + fracturing depend on steel properties.

Cliff is very smart, coupled with super duper passionate about cutting implement related matters... He earned my respect. As for his stropping & edge stress/de-stress assertions, I question that grossly generalization based on a subset(minor not major) of the whole range of sharpening (manual & power). Workable steel edge properties covers a wide range of behavior when interact with abrasives + forces. I see that range spanning as vast as from gum to glass. Nowaday, steels ht for high strength (says 60+rc) and many are high alloy. They are less ductile, so most likely fracture when encounter force exceed yield strength or can 'set' one/twice time past elastic region. As you can see why, I have difficult time seeing how undamaged/good steel can flop around.

I don't totally disagree, I just object to generalization on something of whence the majority of users are experiencing otherwise. I pretty much read everything Cliff posted (on his site & Spyderco). His stuff usually very thoughtful & logical and convincing too but me trust I - hahahahaha. I got myself into metallurgy (wanna be) because issues like these, now I feel like I know even less... well, didn't stop me from yakking up a storm eh!
Click to expand...

Haha thanks for the post man, I also respect what you say a lot ;)

in the 1st pic what was important to note was that it looked like the second pic before stropping, then stropping only 10 passes brought up a wire-edge/burr. That was what I was pointing out =)

But you are right in that I think more research needs to be done and documented. I think it also depends on HOW you strop as well as this is a big factor that affects the apex.

Omega, try adding a micro bevel and seeing how that helps, I would love to hear the feedback! =)
 
Okay, I ran the apex over my stone until the chips were gone. I then sharpened it at 25° then gave it a 30° microbevel. It's cutting like a champ again and doesn't get hung up on annoying chips. :)

YT7KaGa.jpg


Thanks for the advice guys.
 
Omega Leather Works said:
Okay, I ran the apex over my stone until the chips were gone. I then sharpened it at 25° then gave it a 30° microbevel. It's cutting like a champ again and doesn't get hung up on annoying chips. :)

YT7KaGa.jpg


Thanks for the advice guys.
Click to expand...

Holy sweet baby Jesus that looks awesome. :thumbup::eek:;):cool:

My contego needs a new edge but it's part serrated so it'll never look that nice IMHO.
 
Great job man! turned out sweet and you are right, those chips would get annoying! most of my kitchen knives are rough shape, with the exception of me keeping a few razor sharp. But my EDC is always arm hair shaving on a day to day basis, with NO CHIPS :mad: hehe great job! :thumbup:
 
Lookin good. Your contego sure is getting some pampering recently. I bet the ol girl feels like a million bucks again.
 
bluntcut said:
Josh, 1st pic is a wire-edge/burr (i.e. thin & damaged). Strop with abrasive is just a very soft stone (flex degrees depend on substrate stiffness). And there is steeling (with smooth rod) - now we are talking about plastic flow + flipping + fracturing depend on steel properties.

Cliff is very smart, coupled with super duper passionate about cutting implement related matters... He earned my respect. As for his stropping & edge stress/de-stress assertions, I question that grossly generalization based on a subset(minor not major) of the whole range of sharpening (manual & power). Workable steel edge properties covers a wide range of behavior when interact with abrasives + forces. I see that range spanning as vast as from gum to glass. Nowaday, steels ht for high strength (says 60+rc) and many are high alloy. They are less ductile, so most likely fracture when encounter force exceed yield strength or can 'set' one/twice time past elastic region. As you can see why, I have difficult time seeing how undamaged/good steel can flop around.

I don't totally disagree, I just object to generalization on something of whence the majority of users are experiencing otherwise. I pretty much read everything Cliff posted (on his site & Spyderco). His stuff usually very thoughtful & logical and convincing too but me trust I - hahahahaha. I got myself into metallurgy (wanna be) because issues like these, now I feel like I know even less... well, didn't stop me from yakking up a storm eh!
Click to expand...

Well said!
Both stropping and steeling defy any attempt to make blanket statements regarding. Stropping could potentially run the gamut from old-school knife board work with large loose grit to stropping on plain horse hide.

FWIW, I have seen rolling of any sort very seldom with any form of stropping with exception of backhoning on waterstone with very acute edges. At that point one must use very light pressure, and even then there is some steel removal ongoing in the region subject to lateral swaying. What might be waving is also being removed. Even then, the effect can be controlled with light pressure and strong angle control.

As for smooth steel burnishing, despite its long history and common usage is still one of the least understood methods of finishing or maintaining an edge (IMHO). The effect of smooth steel (or glass) burnishing varies widely depending not only on the steel type and RC, but the starting edge finish has an effect, as does angle and direction of the burnishing contact - the amount of pressure goes without saying.

As long as the edge isn't being drawn out to a wire or swayed to the point of brittle failure, retention should be fine and an actual improvement, especially on lower RC cutting tools - done repeatedly with no other preparation it will lead to failure one way or another.

To the OP, nice work! I would have ground it down over time and slowly increased the angle as I went, but is proven I am willing to tolerate small chips and dings as long as the rest of the edge is nice and sharp...

Martin
 
Martin!

Funny, this website is like a city. I run into people I haven't talked to every now and then, and it's always a pleasure. My screen name used to be StrigaMort btw. I'm on the boards every day, but usually it's in the sheaths forum. Nice to visit the old stomping grounds. Is Ohallum still around? I've seen Jason B, Chris A and obviously Blunt cut.

I do think the edge will be just fine. The retention may have given me the opportunity to be a little overzealous in how aggressive I'd get when cutting things. I'll be a little more careful this time around. Ceramic plates, zip ties, fiber banding... Shouldn't be terribly difficult to avoid. :D
 
The answer is simple.

Send it to BM with 35 bucks and get a new blade.
 
uxo2 said:
The answer is simple.

Send it to BM with 35 bucks and get a new blade.
Click to expand...
:) Haha, funny, but I love my blade. I spent some time getting the cerakote off, I don't really want to monkey with a new blade. Now if I could just buy a new blade outright I'd be all over that!
 
Omega Leather Works said:
:) Haha, funny, but I love my blade. I spent some time getting the cerakote off, I don't really want to monkey with a new blade. Now if I could just buy a new blade outright I'd be all over that!
Click to expand...


Unfortunately. You cant.

send it in and get a NEW satin blade.

They re-bladed a 740 Dejavoo. And it was like new again.


But seeing as to you want to keep it. I would stone wash it.
and re grind to your preferred edge angle.
 
You must log in or register to reply here.
Back
Top