When is time to change a knife or reshape the bevel?

[Jan]

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

[Ken S]

Well stated, Jan.

Ken

[Herman Trivilino]

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.

[WolfY]

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.

[Ken S]

Good thoughts, WolfY.

Ken

[Jan]

May be you know the famous article How to Sharpen Everything by G. Daniels published in Popular Science, Oct. 1964.



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.

[stevebot]

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.

[Ken S]

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

[WolfY]

Jan, this is nice nostalgy from the 60's. Thanks. I was about 1 yr old then

[WolfY]

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.

[SharpenADullWitt]

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.

[Jan]

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

Jan

[WolfY]

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.

[Jan]

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