Today's chef's knives are shaped as triangle with straight or little concave face. I guess some of the reasons this shape is popular is easier production and less effort to cut.
As we grind them the edge is creeping up and the meeting point of the bevel and edge is widening a little.
When is the time to either reshape the bevel or buy new knife?
Attached is an illustration of sharpening out 9mm from the original 40 showing how the meeting point of the edge and bevel are changed from 0.85mm to 1.2mm. By the way I used bevel of 1dgr on each side.
What is your opinion/ thoughts?
Recently I have attached link to Victorinox guidance for re-shaping their knives. I think it may be useful for your considerations. :)
https://assets.victorinox.com/medias/servive-cut-drinding-sharpening-en-nov2012.pdf?context=bWFzdGVyfGN1dHwxNzIyNzd8YXBwbGljYXRpb24vcGRmfGg1MC9oZWUvODc5ODIzOTM1OTAwNi5wZGZ8ZGJmOGVkMGRlODEzMGExYTY3Mjc4Y2U0ZmI3NmIwMzAwZjEwZmM1MzIzOWFmYjhjYzE3NTE0NTU0YTk3ZWRlNw
Jan
Excellent topic, WolfY, and excellent reply, Jan.
I do not have a good answer for this. It is a relevant question for Tormek knife sharpeners and one for which we will soon have some guidance from Sweden.
Ken
John Juranitch says that knives should be .020" (0.5mm) a quarter inch back from the edge. This jives with the Victorinix 0.4 to 0.6 mm, although they do not say how far back is considered "the edge"
Steve, I believe you have discussed this before, however, for the benefit of the forum, would you please discuss what you would do if a customer asked you to sharpen a knife which needed thinning?
Ken
Made this case study.
According to Victorinox with this case study parameters we have about 3.7mm before having to grind the bevel in order to keep the knife with similar characteristics as origin. Interesting.
And tanks Jan for the PDF. It really helped.
Quote from: stevebot on August 18, 2016, 03:23:24 PM
John Juranitch says that knives should be .020" (0.5mm) a quarter inch back from the edge. This jives with the Victorinix 0.4 to 0.6 mm, although they do not say how far back is considered "the edge"
Steve,
thanks for mentioning John Juranitch. :)
Attached there is the relevant section of his famous article.
From his sketch we can derive that the angle of the tapered blade is circa 9° which is much more than we can see at modern kitchen knives. My older Solingen boning knife has the angle of the blade some 6° ("relief" in Juranitch terminology). ;)
Jan
Thanks for posting the article, Jan. I put it in ibooks on my ipad.
Ken
Here is the full article
http://sharpeningmadeeasy.com/Juranitch1977Feb.htm
Quote from: Ken S on August 18, 2016, 04:14:20 PM
Steve, I believe you have discussed this before, however, for the benefit of the forum, would you please discuss what you would do if a customer asked you to sharpen a knife which needed thinning?
Ken
Ken,
this is tricky question. We know well how to sharpen an edge angle but not how to ground a defined thickness in a certain distance from the edge. ;)
Jan
Quote from: stevebot on August 19, 2016, 12:39:46 AM
Here is the full article
http://sharpeningmadeeasy.com/Juranitch1977Feb.htm
Juranitch is known supporter of dry honing. For me the figure from his article in Popular Science is not fully convincing.
https://photos-4.dropbox.com/t/2/AAC0D36HZhtlopMJkoBsGO94JKlJd98ywvwMk4qpM3fSdQ/12/484370172/jpeg/32x32/1/_/1/2/Jurantich_oil_vs_dry_honing.jpg/EOiO4vYDGF8gBygH/vBFdxnuS_KcwB8kg4JQOcM-656bBpJ_bXv3R7Ki0nRw?size=1600x1200&size_mode=3
Jan
Jan,
I agree the issue of knife thinning is tricky. I certainly would not feel comfortable doing it. It is, however, an issue knife sharpeners must occasionally confront. As much as I value the handbook, there are certain important things it does not cover. This is one of those things.
If the design of the Tormek is capable of thinning, we should know about that technique. Those of us who are willing to learn that skill will do so.
If the design parameters of the Tormek do not include knife thinning, and that operation should be left to more specialized machinery, the handbook should state that. Every machine has its parameters.
Ken
Ken,
I agree with you. :)
Fortunately hollow ground blades only seldom need blade thinning, because their thickness slowly increases with the distance from the cutting edge. When necessary, thinning can be done on Tormek by applying a patient step by step procedure with very small material removal in one step followed by thickness measurement.
The need to thin the blade is more frequent by V ground blades (e.g. butcher's knives) because their thickness more rapidly increases with the distance from the cutting edge. This can be done on the side of the grinding wheel, freehand or supported by the tool rest or some homemade platform.
Thinning of convex ground blades (e.g. cleavers) using Tormek is for me hardly imaginable.
Jan
Jan,
My point is that either thinning is or is not a function which can or should be performed with the Tormek. If this is a Tormek compatable function, I would like to see it described in the handbook. If it is not, I would like to see this advised in the handbook. Every tool has functions it perform well, some functions doable but not in the primary design, and some functions which are not practical or possible. I would like to see this discussed in future editions of the handbook and posted on the forum for present use.
Ken
Ken, I understand your point and would also appreciate to read about knife thinning in the future edition of Tormek handbook but it may be a long-distance run.
Because the issue of knife thinning is tricky I have posted my opinion that the Tormek is capable of thinning hollow ground blades and with some restrictions also V ground blades but not convex ground blades. My opinion is open to discussion.
I hope I've explained myself well.
Jan
Well stated, Jan.
Ken
I'm not brave enough to thin a knife on a Tormek. If I had an expensive knife in need of thinning I'd send it off to be done by a professional, just as I do with my carbide-tipped circular saw blades. Of course, I might give it a try on a cheap knife, but who would want to thin a cheap knife?
For example, I have an old pocket knife that belonged to my wife's father. I've reshaped one of the blades because the tip was broken and now when it's closed it goes so far into the handle that it's hard to retrieve. It's been sharpened so many times over the years that it does need thinning, but I probably won't ever bother with it.
I think that thinning issue is mostly related to knifes that are sharpened a lot like kitchen knives the question of knife price is not relevant. But the function is definitely.
As the recommendation by Victorinox are our guideline example I will stick to their parameters.
I believe that when sharpening the knife so many time that it's losing almost 25% of it's width we are also starting to lower the angle of the edge to compensate for the changes. When it becomes too awkward it's time to reshape the blade and give it a new bevel. This bevel is easily made with Tormek or strait surfaced grinder, as its very small. It's impossible, and IMHO not wise to grind all the primary bevel.
And yes sometime the client has to understand that it's time to buy new knife.
IMHO a butcher or chefs knife that has been used so much, has paid it self many times and can be changed.
That's also one of the arguments to sharpen with Tormek, as it is removing minimum steel, prolonging the knife's life.
Good thoughts, WolfY.
Ken
May be you know the famous article How to Sharpen Everything by G. Daniels published in Popular Science, Oct. 1964.
(http://img21.rajce.idnes.cz/d2102/11/11771/11771137_37021e568ec44478b9ce7dc74d286378/images/How_to_sharpen_everything_front_image.jpg?ver=0)
His recommendation concerning blade thinning is following: "Unless you're skilled grinder, leave this to a pro."
Jan
P.S.: https://books.google.cz/books?id=1yUDAAAAMBAJ&pg=PA2&hl=cs&source=gbs_toc&cad=2#v=onepage&q&f=false
The article starts on page 174.
My personal solution for thinning is to take the knife to the local wet grinding service that serves the restaurants and have them hollow grind it. Their work is not pretty but is functional. $2 for a stamped knife and $5 for a forged knife of any size.
The expression, "fools rush in where angels fear to tread" comes to mind. If someone like Steve chooses not to thin knives, I will follow hisexample. All the more reason for Tormek's jigged minimal metal removal philosophy.
Ken
Jan, this is nice nostalgy from the 60's. Thanks. I was about 1 yr old then :)
Quote from: stevebot on August 21, 2016, 05:12:25 PM
My personal solution for thinning is to take the knife to the local wet grinding service that serves the restaurants and have them hollow grind it. Their work is not pretty but is functional. $2 for a stamped knife and $5 for a forged knife of any size.
Steve,
You can't get service like that everywhere. Hollow grinding with wet wheel, big like that?
Thinning a knife that is 2.2mm at the back and about 0.6 at the cutting bevel would be too risky and make the knife ugly. IMHO.
I'd rather spend the time and money to make a nice new (small) bevel with the Tormek. And of course I would consult the client about it before.
What Steve mentions, we have around here. They are also the ones who professionally sharpen, manual and automatic slicer blades. That might be something that may help someone find them in the future. (and professional, slicer blades have been discussed here before, a couple times over the years. It was a take to the pro's, don't try it on the Tormek thing, as it isn't designed for it)
Knives ARE consumables. One does have to judge for themselves if it is a matter of a broken tip, verses not having another knife, etc.
Quote from: WolfY on August 22, 2016, 04:55:59 AM
Jan, this is nice nostalgy from the 60's. Thanks. I was about 1 yr old then :)
Wolfy,
yes it is nostalgic but surprisingly true even after more than 50 years! Also the Part 1 of this series: Yard and Garden Tools is still useful reading. You can learn here at what angle you should sharpen your shovel or mattock, certainly not using Tormek. The article is here:
https://www.dropbox.com/s/ynwpvqqzjj1gqn9/Daniels_Part_1_Yard_and_Garden_Tools_1964.pdf?dl=0 (https://www.dropbox.com/s/ynwpvqqzjj1gqn9/Daniels_Part_1_Yard_and_Garden_Tools_1964.pdf?dl=0)
Jan
I think In lots of situations described, today I'd use an angle grinder instead of file.
But it certainly is nice to see this old article actual now as then. That was the media then.
Yes, Wolfy, you are correct! :)
Just today I have sharpened my wife's shovel using an angle grinder with lamellar disc. The disc has surprisingly deep cutting. I have sharpened the bevel at about 45°. Now it easily penetrates the earth and cuts small roots.
Jan