or Connect
ChefTalk.com › ChefTalk Cooking Forums › Food & Equipment Reviews › Cooking Knife Reviews › What Is Reprofiling, Exactly?
New Posts  All Forums:Forum Nav:

What Is Reprofiling, Exactly?

post #1 of 18
Thread Starter 

To reprofile a knife to a final edge of, say, 20 degrees.....

Would you begin your sharpening at a higher (ie: 25 degrees) or a lower (ie: 15 degrees) angle than your desired bevel?

I'm guessing it would be higher, but...

 

Don't quite understand this part, though I know essentially what reprofiling is.

 

Thanks.

post #2 of 18

Either higher or lower, your preference and that of the blade.  Your blade may perform "better" with a profile different that what it was manufactured with.  It's all about experimentation to see what you prefer.

Best and I'm a foodie.   I know very little but the little that I know I want to know very well.

 

-T

Brot und Wein
(1 photos)
 
Reply

Best and I'm a foodie.   I know very little but the little that I know I want to know very well.

 

-T

Brot und Wein
(1 photos)
 
Reply
post #3 of 18
Thread Starter 

I have some blades that have been "oversharpened" over time.  Want to thin above the edge.

post #4 of 18

The "best" angle and edge geometry for any given knife is as acute as you can get it without compromising durability. 

 

Restricting ourselves to talking about knives which are sharpened on both sides:  Some knives work best with simple, flat bevels.  Others work best with more compiex, multi or convex bevels.  The same is true about various ratios of asymmetry.  Consequently, any conversation about "profiles" should include at least some mention of geometry as well as bevel angles.  

 

To reprofile a knife to a final edge of, say, 20 degrees, would you begin your sharpening at a higher (ie: 25 degrees) or a lower (ie: 15 degrees) angle than your desired bevel?

 

To achieve any given final edge angle, you MUST begin by profiling the knife either to that angle, or an angle less acute.  If you begin by profiling the knife to a more obtuse angle, you won't be able to the edge on the stone when you try to sharpen the more acute, final angle. 

 

The rationale behind beginning with a more acute angle than the desired, final angle, is to end up with a double bevel* when you sharpen the final angle; and the rationale for a double bevel is an edge which seems as sharp as the more acute, secondary angle,* but is as unlikely to "collapse" (get dinged out of true) as the more obtuse, primary angle* which is on the actual, cutting edge. 

 

If, for instance, you profiled (or sharpened or thinned) a 15* secondary bevel, and sharpened a 20* bevel on top of that (without grinding the 15* angle all the way to the knife face), the angles would be expressed as 20*/15*. 

 

There's another thread which has some discussion about what's involved in choosing and profiling a multi-bevel.  A lot of your remaining questions will be answered by posts 4, 7 and 10. 

 

BDL

 

*Note that the italicized terms, double bevel, primary or secondary angles, and primary or secondary bevels are all ambiguous.  A knife which is sharpened on both sides is often called "double beveled" in order to differentiate from a knife with a chisel edge, which is often called "single beveled."  The terms primary and secondary are often flipped, depending on the sharpener.  There's no right or wrong with these things, but if you're going to use or even read them it's important to know what the other person is talking about.

post #5 of 18
I don't know if oversharpening is the clearest term, but when you sharpen the knife without ever thinning behind the edge, yes, it will become thicker and thicker. The edge is slightly moved towards the spine, and because of the taper, the blade is thicker in that area.
You may build a relief bevel behind the actual edge.
To do so, choose an angle much lower than you're used to, and sharpen as you normally do. The scratch pattern will show that you don't actually reach the very edge. Go on until you're at some 1mm from the very edge. From there on, go further with your normal angle.
If you sharpen @15 degree per side, a relief bevel @10 will greatly enhance performance.
More on this subject in the following excerpts from Chad Ward's An Edge in the Kitchen:



http://forums.egullet.org/topic/117052-an-edge-in-the-kitchen/
post #6 of 18

Use a good jig, such as a rod guide sharpener like one of the Edge Pros, along with a good angle finder (like a digital angle cube), and it's pretty easy to create a true, double bevel with similar secondary and primary angles such as 15/10.  Easy, but time intensive, because in essence you have to sharpen the knife twice, sharpening each bevel angle twice -- sharpening even the more acute bevel to a fairly high degree of polish.     

 

But if you sharpen by hand, the most efficient method for laying in a double bevel is to create a micro-bevel, rather than a true multi-bevel.  It's nearly impossible -- even for someone who sharpens at my level of accuracy -- to lay in a 15/10 double bevel and have those numbers represent anything like actual 15* and 10* angles. 

 

Some knives work better with multi-bevels, others do not.  For those which do not, laying in a true multi-bevel is a substantial waste of time.  On the other hand, since a micro bevel doesn't take long at all you might as well try it. 

 

Tell me what knives you're sharpening and I can probably suggest some angles.

 

BDL

post #7 of 18
Thread Starter 

Hey, thanks for the replies.

I am just beginning to gather a few decent knives, but here is what I have right now:

 

Forschner Chef's, 8", 10" and 12"

Forschner Cimitar 12"

Richmond Artifex 210

Some Old Hickorys.  I like looking at these.  Makes me feel like I'm back in 1776.

A Washington Forge 10" that I think is made from some other-worldly material.  Like trying to sharpen a brick with a sponge.  Don't know where that came from.

A pretty nice French Sabatier 8".

A Swibo 6" boning knife.

etc.

 

I keep going back and looking at the Kikuichi TKC's.  What do you think??

 

Thanks.

 

Seems to me from what you're saying is to sharpen at 18-20 degrees, then switch to 15.  That right?  I know I will leave the store knives at 20, though, except for the ones I'm using.

I do have an Edge Pro Professional model, but I haven't started learning how to use it yet.  Watching videos and reading forum posts for a few more days.

post #8 of 18
Seems to me from what you're saying is to sharpen at 18-20 degrees, then switch to 15.  That right?

No.  You keep getting this upside down.  If you're sharpening a multi-bevel always start with the more acute (lower number) angle, then move on to the more obtuse (higher number) angle -- if for no other reason than it's geometrically and physically impossible to do it the way you're suggesting. 

 

Also, unless you're using an accurate jig of some sort, if you're determined to sharpen a multi-bevel, I strongly suggest doing the primary (cutting) bevel as a micro bevel only.  I described how to do that in the other thread I already linked, in post #10. 

 

If you want to sharpen a flat bevel, which is perfectly fine for most knives, start with a very fast, coarse stone, one capable of moving metal quickly, and sharpen whatever angle you want making sure to hold the desired angle.  A coarse stone will not only make the process go faster, it has less tendency to "click-in" on the existing edge.  Be very careful to get the angle you want, and be very conscious to hold it consistently.  I strongly suggest using the Magic Marker Trick to aid you in establishing an appropriate edge.  If you don't know how to use the Magic Marker Trick, that's something we can discuss.

 

Specific Recommendations for Your Knives:

  • Forschner Chef's, 8", 10" and 12": 15* flat bevel, 50/50;
  • Forschner Cimiter 12": 15* flat bevel, 50/50;
  • Richmond Artifex 210: 15* flat bevel, 50/50;
  • Some Old Hickorys.  I like looking at these.  Makes me feel like I'm back in 1776:  These are heavy duty champs, cheap as cheap can be, cruder than my college roommate reciting dirty limericks while lighting his farts, and I like them too.  Either a flat 20-22 or a 20-22/15 micro-bevel with 50/50 or 60/40 symmetry.  Ontario did some retooling for the Old Hickory line fairly recently.  Knives made from the eighties through the early years of this century were very inconsistent, and some are so difficult to maintain (too thick, poorly hardened, huge carbides, etc.) they're not worth keeping. 
  • A Washington Forge 10" that I think is made from some other-worldly material.  Like trying to sharpen a brick with a sponge.  Don't know where that came from:  Don't know for sure.  Most el-cheapos can't handle anything less than 20*.  I wouldn't waste a lot of time or worry on this knife unless you really love it;
  • A pretty nice French Sabatier 8": 20/15 micro-bevel with 50/50 symmetry if its stainless; 15* flat bevel, 60/40 if its carbon;
  • A Swibo 6" boning knife:  Swibo are the Wenger equivalent of Forschner by Victorinox Fibrox.  They're made in the same way from the same alloy and get the same 15* flat bevel, 50/50.  But because boning knives have such narrow profiles they get used up with frequent sharpening, and need replacement fairly frequently; and
  • etc.:  Depends.   

 

BDL

post #9 of 18
Quote:
Originally Posted by boar_d_laze View Post

...A pretty nice French Sabatier 8": 20/15 micro-bevel with 50/50 symmetry if its stainless; 15* flat bevel, 60/40 if its carbon;...

BDL

I really like either something shallower than the 60/40 approach with my very old Sabatier carbon steel knives.  That last little "obtuseness"  feels just right for the grab of my palm when it comes to testing sharpness.  A shallow angle nearly parallel to the stone followed by a steeper angle to finish the edge.  Forty years of sharpening have taught me THAT with my 'metals'!!!!!!!!!!!!!!!!!

 

And I gotta' state that finishing with a soft arkansas backed with a fine surgical stone is THE best combination, especially when it comes to backing up with steeling - after a cutting section for pate en terrine.

 

As I'm cutting meat, fat back and shoulder for  a home boy pate, steeling really does the trick on my knife.  Awesome.


Edited by kokopuffs - 2/25/13 at 1:49pm

Best and I'm a foodie.   I know very little but the little that I know I want to know very well.

 

-T

Brot und Wein
(1 photos)
 
Reply

Best and I'm a foodie.   I know very little but the little that I know I want to know very well.

 

-T

Brot und Wein
(1 photos)
 
Reply
post #10 of 18
Thread Starter 

BDL, the light just came on. Dimly, possibly, but on.   I'm sometimes, probably always, very thick-headed.

You really don't know how I hate to ask this, but how do you do "thinning"  rather than sharpening??

 

Don't scream.  I'm sensitive.

post #11 of 18
As far as I know, there hasn't been any screaming, by anyone, in this thread, yet.
I hope BDL will respond to answer your question. My answer would be: there are different thinning techniques, but here, thinning is just sharpening at a lower -- more acute -- angle.
post #12 of 18
Thread Starter 

It was meant as a joke.

post #13 of 18

Thinning, sharpening at a shallower angle where the edge of the blade is held nearly parallel with the coarse sharpening stone.

Best and I'm a foodie.   I know very little but the little that I know I want to know very well.

 

-T

Brot und Wein
(1 photos)
 
Reply

Best and I'm a foodie.   I know very little but the little that I know I want to know very well.

 

-T

Brot und Wein
(1 photos)
 
Reply
post #14 of 18
Thread Starter 

I sharpened my first knife with my edge pro last night.  It was a 6" Old Hickory that's been around here for around 40 years.

As far as sharpness goes, it went very well.  Sharpened to an 18* edge, starting with the 120 and progressing through the stones to the 2000 tape.  Very sharp.

 

The problem I had was that both sides of the edge are uneven, with one side of the edge ending up with a wider bevel.

 

The side with the narrowest bevel was the one sharpened with my left hand controlling the stone, so I feel fairly sure that what I did wrong has to do with my using more pressure with my right hand controlling than I did with my left. I also may have moved the stone faster with my right hand.

 

To even this out, can you just sharpen one side to even it out, or should I sharpen both sides, using more strokes on the narrow one?

 

Another Edge Pro question I have is when you guys sharpen a gyuto, how much overhang do you have from the table edge to the knife edge.  Just seems like a lot, but maybe it doesn't make any difference.

 

Thanks much for the replies, I appreciate it a lot.

post #15 of 18
I hope BDL will respond to answer your question.

 

Talking about this stuff it's important to be very clear about terms, because definitions are inconsistent.  Different people use the same terms differently and with an equal claim to being right.  As long as we're sure we're talking about the same thing, great.

 

"Thinning" is a term you see a lot on the knife enthusiast boards, but it's not one I like to use ordinarily, or at least without a lot of explanation, because it's ambiguous.

 

When I talk about "thinning," I usually mean one of three things:

  1. Some blades have a more obtuse face grind and/or edge angle at the heel than further forward (towards tip).  Some sharpener/users feel they can improve the performance of the knife by making either or both more acute;
  2. When profiling a double-bevel* the sharpener creates a secondary bevel* between the cutting bevel and the face grind which is more acute than the cutting bevel on the way to profiling a double bevel;* and
  3. Re-profiling edge bevels with a coarse stone in order to return them to their desired angles after they've become increasingly obtuse with repeated sharpening.  For freehand sharpeners, it's usually a good idea to do this every third or fourth sharpening.   When I talk about re-profiling the original angle, or profiling an entirely new angle, I personally don't use the term "thinning;" but that's me.  

*Note:  The terms double bevel and secondary bevel can be ambiguous, too.  Here, double bevel refers to a multi-bevel with two steps; while secondary bevel signifies the transitional bevel between the more acute face grind and more obtuse edge bevel. 

 

The problem I had was that both sides of the edge are uneven, with one side of the edge ending up with a wider bevel.

 

The side with the narrowest bevel was the one sharpened with my left hand controlling the stone, so I feel fairly sure that what I did wrong has to do with my using more pressure with my right hand controlling than I did with my left. I also may have moved the stone faster with my right hand.

 

To even this out, can you just sharpen one side to even it out, or should I sharpen both sides, using more strokes on the narrow one?

 

You want your bevels widths even all the way along the length of the knife up to where the edge curves towards the tip.  You also want to keep your bevel ratio constant at the desired bevel.  If you have "low" spots on either side, you "section" the knife by giving those spots extra sharpening.  At this stage of your sharpening career you want very definite, crisply defined, and straight bevel shoulders at the transition between knife face and edge bevel. 

 

In order to see how well the shoulders are defined, as well as see the low spots as they develop, use the Magic Marker Trick.  The Magic Marker Trick is one of the most valuable things any beginner can do to help himself. 

 

If, after you learn to coordinate the movements it takes to use an EP, and after you learn the appropriate amount of pressure (as little as possible) it takes for efficient sharpening, you still find that one side sharpens more quickly than the other, then... Yes, you should consistently give the side which requires more time more time.  This might seem obvious when you read it, but it's one of those things which requires either explanation or experience before it jumps out at you.  In the meantime, the sides are probably sharpening at the same rate because you're using too much pressure on one side, and way too much pressure on the other. 

 

Another Edge Pro question I have is when you guys sharpen a gyuto, how much overhang do you have from the table edge to the knife edge.  Just seems like a lot, but maybe it doesn't make any difference.

Depends on the length and width of the knife.  You should always have as much of the spine as possible against the table's stop.  You'll have to rotate the knife a little to get to the tip, but that's okay.   

 

BDL

post #16 of 18
Thread Starter 

I'm not upside down anymore, BDL.  What was throwing me, was the term "more acute".  I was thinking of the angle of the cutting edge itself, not the sharpening angle.

 

I'm not explaining this too well, but I do understand now.

 

Thanks much for your patience.  Also, your other info is beginning to sink in now, too, as is that from the others trying to help.

 

There were a couple of merit badges I didn't get in Boy Scouts...knife sharpening was one of them.

My goal now is to put my shiny stainless steel $500 ChefsChoice Commercial out of business.

 

I know I'll have more questions, and I appreciate everyone's help. 

 

Thanks again.

post #17 of 18
Quote:
Originally Posted by Raibeaux View Post

 ............the angle of the cutting edge itself, not the sharpening angle.

 

???????????????

post #18 of 18
Quote:
Originally Posted by Raibeaux View Post

BDL, the light just came on. Dimly, possibly, but on.   I'm sometimes, probably always, very thick-headed.

You really don't know how I hate to ask this, but how do you do "thinning"  rather than sharpening??

 

Don't scream.  I'm sensitive.


LOL!  I hear ya... smile.gif  This has been another informative thread for us guys trying to figure out primary, secondary, and micro bevels, and as well as acute vs. obtuse angles!  At least for my obtuse brain. I get to read it all at least twice then it starts to really make sense. Thanks also to BDL, as usual I should note...

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Cooking Knife Reviews
ChefTalk.com › ChefTalk Cooking Forums › Food & Equipment Reviews › Cooking Knife Reviews › What Is Reprofiling, Exactly?