First reprofiling, what should I be aware of?

Discussion in 'Sharpening Station' started by DisconnectedAG, Apr 25, 2019.

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  1. Apr 25, 2019 #1

    DisconnectedAG

    DisconnectedAG

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    So my dad has an old "Sabatier 4 star" 240mm chefs that has a beautiful Arc de Triomphe in the middle after years of careless pull through sharpening. I'm visiting this weekend and wanted to have a go at repeofiling it.

    The steel is the normal Western stainless I'm guessing some kind of CroMoVa15. I don't know the HRC but I think it's safe to assume something in the 58 range.

    BecauW I'm flying i don't want to bring all my stones, and I was planning to bring a Shapton Pro 320 and a 1k/4k combo or a Chosera 1.5k.

    Unfortunately I don't have pictures of the knife, but if you put it flat on a board you see the light through the arch.

    Will these stones be enough? I won't have several hours to spend, unfortunately, so only want to do this if I have a reasonable chance of success within the time frame. Otherwise I'll take it back with me and fix it in due time.
     
  2. Apr 25, 2019 #2
    It sounds like a lot of work to be hones. You will first need to correct the profile so that the arc disappears and then thin the knife accordingly. How much work it will be will depend in the first place on how large (tall or deep) the arc is. The Pro320 is a good stone to tackle this (something like a Bester 220 or Sigma 240 would be faster though). Unless the over-grind you want to correct is only very gentle it will most likely be several hours to get this job done (though Sabatiers are not super hard or wear resistant, so maybe it will not be that bad)
     
  3. Apr 25, 2019 #3

    DisconnectedAG

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    Thanks, this is really helpful. I will probably confiscate it for fixing then, so I can go at it at home when I have more time. A very stupid question - when it comes to getting the basic profile straight before profiling, would it work to take it to a rough stone outdoors or some concrete? My thinking is - as I dont have anything in the 100-250 grit range I can do the super rough stuff on any random stone, then use my 320 to profile it properly and thin, and then finish on maybe 1.5k.
     
  4. Apr 25, 2019 #4
    You're welcome. I guess that most 'rough stones outdoors' would be too slow, just coarse. Consider also the option of using wet (WD40 works well here) sandpaper mounted in some fashion on some hard surface for the coarse work. That going to be faster than any sharpening stone. If you go this route get something like Indasa Rhynowet sandpaper as it is of very good quality. Sandpaper for woodworking (paper backing) will not work that well as it will not stand to be used wet most likely.
     
  5. Apr 25, 2019 #5

    Knife2meatu

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    Just about any metal file of better than awful quality will cut that steel and be good and fast for getting the profile straight quickly. The main caveat is that it virtually requires something to hold the blade firmly, ideally a vise.
     
  6. Apr 25, 2019 #6

    Nemo

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    I have used coarse (80 grit) wet & dry sandpaper to do the heavy lifting for this sort of work. This job is a pain in the backside IIRC

    A good file should also work.
     
  7. Apr 25, 2019 #7
    Are sabatiers soft enough to be tackled with a file without damaging it? There is going to be at most 10 hrc points difference between the file and the knife ...
     
  8. Apr 25, 2019 #8

    Nemo

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    Good question.

    From memory, I considered using a file but decided to use sandpaper instead.
     
  9. Apr 25, 2019 #9

    DisconnectedAG

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    Thanks guys, this is super useful. Probably not a project for this trip then, but will try to tackle it later.
     
  10. Apr 25, 2019 #10

    HRC_64

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    Standard german stainless is approx 54-56 and easily reprofiled

    IIRC standard tools have a hardness is around 60
     
  11. Apr 25, 2019 #11

    chinacats

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    I'd consider breadknifing it for the heavy work... I've had success on a sidewalk for the start... it'll save a bit of life on your stone.
     
  12. Apr 25, 2019 #12

    _THS_

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    Be careful fixing knives on soft stones as sp 320 cause you could damage the stone creating big gauges in it. Also using a file is either dangerous and extremely slow so I'd avoid that too. Imho your best options are either sand paper ( wet/dry with wd40 better if on a very flat surface ) or atoma 140. You could also buy one of those cheap coarse stones they sell to sharpen sickles, the one I used was hard af and I paid like 3 euros for it.
     
  13. Apr 25, 2019 #13

    Knife2meatu

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    I'm not even sure what you could possibly mean by "dangerous", but it certainly isn't extremely slow -- and to then go on to recommend an Atoma 140 for something which is likely to crush the diamonds when the pressure is pinpointed under the blade? Laughable.
     
  14. Apr 25, 2019 #14

    _THS_

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    Maybe I missed something but can you please explain me how would you use a file to reprofile a knife? Do you hold file or knife? How do you fix either one or the other when operating?
    Also what's laughable about using the atoma? Isn't it made for heavy metal removal?
     
  15. Apr 25, 2019 #15

    _THS_

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    Aside from what I asked before I think "laughable" could be offensive against someone other opinion. I just gave my pov having fixed and reprofiled many blades, the majority of wich wasn't mine
     
  16. Apr 25, 2019 #16

    ian

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    Is it really so easy to crush diamonds?

    FWIW, I used an atoma 140 to fix a 5mm deep chip in a Mac knife earlier this year. That was a total pita, especially the thinning and polishing, but it worked. Imagine a Sab will be easier.

    I couldn't really tell a difference between atoma pre-work and atoma post-work, but probably I just forget what it was like before.

    Until the profile is sort of close to what you want, I’d recommend ‘sharpening at a 70 degree ange’ or something instead of breadknifing, since the latter takes forever. Then again, I’d listen to the more experienced people over myself...
     
  17. Apr 25, 2019 #17

    ian

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    (As mentioned above, you use a vise.)
     
  18. Apr 25, 2019 #18

    _THS_

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    I am thinking... makers create bevels and polishers create convexity on a daily basis with atoma, I know one that ground uncountable honyaki with atoma... how a soft French blade can even tickle it? We all (I hope) flatten our stones with atoma and stones are (obviously) "harder" than steel
     
  19. Apr 25, 2019 #19

    Knife2meatu

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    Ideally the knife is held stationary, edge toward the sky in a vise, and the file is used to re-profile the edge by running it along the top of the knife. Holding the file's long axis as near to parallel with the blade's long axis maximizes contact area, and if using a file with a multiple-cut pattern, maximizes cutting. As I said before some means of holding the knife is important; and although a vise is ideal, I'm sure anyone could jerry-rig something with a couple of clamps and some scrap bits of wood.

    Perhaps we are speaking at cross purposes however; I'm only recommending the file for flattening the concavity, or recurve happening along the cutting edge of the blade -- the kind of thing which causes some significant section of the blade not make contact with a flat cutting board -- I don't mean to recommend a file for the following re-shaping the edge geometry, thinning and ultimately sharpening the edge -- for that the Atoma is certainly a good choice and a file, a poor one.

    As for how easy it would be to damage an Atoma by cutting into it with a knife (because that would be the analogous motion), I suppose it must depend on the force used. But considering the shape of the contact area would by definition be rather tiny, and how it would be very easy to pinpoint force by pressing down on the spine, I can't see how this wouldn't be exactly the kind of usage which risks causing some local accelerated wear.
     
  20. Apr 25, 2019 #20

    ian

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    Well, whether or not that’s true, if the knife is currently sharp (so that the contact area is thin), you can shave off some significant height by just wiping the blade across the atoma with minimal downward pressure. And once you’ve suitably dulled the edge, there’s more contact area. Not sure there would be any reason to plant a very acute edge on a diamond and bear down.

    Anyway, the atoma worked out fine for me as far as I can tell.
     
  21. Apr 25, 2019 #21

    Knife2meatu

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    @ian : Yes, 'wiping' the blade across the surface of the 140 Atoma with feather weight is how I used to prefer straightening straight razor edges -- and in that case it isn't concern over the Atoma which dictates the light pressure, but rather the radically thin blades -- until I started using a Shapton 120 for this purpose. And in much the same way that it is possible to avoid wearing a groove in the Shapton by wiping over the surface rather than cutting into it, I'm sure it is possible to use the Atoma in different fashions with differing results.

    I think what made me assume the "cutting" method must be what the post had in mind I was responding to, was the warning about "be[ing] careful fixing knives on soft stones as sp 320 cause you could damage the stone creating big gauges in it." -- considering that, as I think we would agree, there's no risk of gouging if one is wiping the edge across rather than along.

    It is in this context that I found the suggestion laughable in my estimation: To recommend the Atoma plate as a better alternative to a metal file (for this task, and considering the OP mentions already having a Shapton 320) would seem to mean recommending a slower, far more expensive tool, which arguably risks more permanent-lasting damage if it is used in precisely the manner the poster was warning about -- albeit with greater forces involved, I would grant.
     
  22. Apr 25, 2019 #22

    ian

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    *like*
     
  23. Apr 25, 2019 #23

    Nemo

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    Post deleted because this had already all been covered.
     
  24. Apr 26, 2019 #24

    DisconnectedAG

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    This is super useful, thanks! I think I will go the sandpaper route as that seems to be the cheapest and safest option. I can improvise a vise at home (kitchen and some G-clamps) for safety.
     
  25. Apr 26, 2019 #25

    DisconnectedAG

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    This is what I was thinking also.
     
  26. Apr 26, 2019 #26

    DisconnectedAG

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    Thanks everyone for the insight. This has been a really useful thread. The benefit I have is that this knife is already in the 'not used anymore' drawer, so I don't have to worry about ruining it. Also it will most likely be quite soft. I don't think I'm in a position to get an atoma plate, as that would be both expensive and my partner is already grumbling about the space my stones use up. Plus - I don't really do the kind of jobs that Atoma's perform best, so I can't justify the spend.

    I will either try a file (using clamps) or use the pavement or some granite outdoors for the basic reprofiling to remove the arch, and then will try to use the 320 for thinning and basic edge setting, working my way up to 1k for polish and 3k (have a no-brand 3/6k brick( for the final polish and see what happens.
     
  27. Apr 26, 2019 #27

    ian

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    Sounds good! Good luck.
     
  28. Apr 27, 2019 #28

    stringer

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    I'm a little late to the party but I'll throw in my 2 cents because this is something I do pretty frequently. I have tried to describe it on here before but it's easier to show so I made a video. I'm still working on learning how to make watchable photographs and videos so bear with me.

    This is a project knife that was in really decrepit shape. It had severe reverse belly. It's an Old Forge 10" Chef Knife. It's extremely similar to Forgecraft. Possibly even made by the same company, just a decade or two later. I fixed it, but not good enough. I was still getting slight accordion cuts when julienneing bell peppers. I purposefully took a few minutes to over grind it in that spot a little more for the purposes of the demo.
    IMG_20190427_082952.jpg

    Then I used the side of a 300 King Deluxe stone with the knife perpendicular to the face of the stone. I ground the edge down until I could feel that there wasn't a bump there anymore. I believe that this is also what people refer to as breadknifing. If you do it on the side of the stone then gouges don't interfere with regular sharpening use. A brick or concrete or something would work too I suppose. It only takes a couple of minutes usually, but then your edge will be flattened right there and need to be thinned and sharpened.



    Profile fixed, but not thinned and sharpened

     
  29. Apr 27, 2019 #29

    Knife2meatu

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    @stringer : Have you ever found your King 300's cutting to slow down considerably to the point of needing to recondition the surface?

    Mine did so regularly and I'm wondering if it was principally a function of the steels I've been taking to it -- I believe you have nicer carbon steel blades than I have access to, and I wonder what your experience has been.

    I eventually decided to ignore some warnings I've seen and let it soak permanently and have been much happier with it since; and I wonder if it's due to the what I've been using it for or not.
     
  30. Apr 27, 2019 #30

    ian

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    I also permasoak my King 300 now, and much prefer the feel. I don’t remember it being particularly slow on my high end carbons, but it felt a little like nails on a chalkboard to me before.
     

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