The process of knife making and Edge retention

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beendare

Joined
Nov 25, 2006
Messages
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Does the process of developing the blades shape and grinding the bevel weaken the Temper?

I'm curious as to the process and if there are wide variations in edge toughness and edge retention within the same steel. For example, will all of the blanks of CPM S30v have the same characteristics assuming they have the same bevel angle? I am not asking for anyones proprietary processes here....but it seems to me I have seen some knife steels from the mass producers (that are very close to the same bevel angle) be better than others.

My anecdotal observations are anything but scientific...namely I'm starting a discussion on the subtle differences in knife development that either add to...or subtract from a higher quality blade.

I am assuming an outfit like Benchmade or Buck doesn't retemper a blade after it's been shaped and bevelled...but I could be completely in left field.
 
FWIW, I've seen the Ankerson edge testing data...and the Knife steel nerds chart...along with others.

I'm more interested in whether the life making process can affect the edge and quality of the original blank. An example could be possibly getting the steel too hot when either cutting the shape or grinding the bevel.

If I sound like I don't know what question to ask- you would be correct!

At least I know the right place to go to get insights into this......grin
 
J

Thread 'Burnt Edges'

In your experience, is there any truth to what people say about sharpening a knife when you get it because the steel at the edge of new knives is no good? "Burnt" is a word I hear a lot.

I asked David Mary David Mary this earlier today and he gave me his input and now I pose this question to the forum. I’d love to hear from any and all.

Thanks, guys.
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This would be best addressed in the knife makers area. Moving there now.
 
I've always thought that in stock removal knife making the blade is heat treated when the bevels have been ground. Post heat treat is only finishing up the blade and adding the edge.
 
For stock removal, even if you take it as far as possible before heat treatment, there is generally some post heat treatment grinding to be done. This isn't an issue for the main bevel since the volume at the apex of an unsharpened edge is large enough not to overheat. It's all about how you sharpen and create the final bevel. I do that by hand with diamond stones.
 
Yep, that's what I meant by "finishing up the blade and adding the edge." Thanks for clarifying my inadequate statement.
 
Richard338 said:
For stock removal, even if you take it as far as possible before heat treatment, there is generally some post heat treatment grinding to be done. This isn't an issue for the main bevel since the volume at the apex of an unsharpened edge is large enough not to overheat. It's all about how you sharpen and create the final bevel. I do that by hand with diamond stones.
Click to expand...
Ok, makes sense…but outfits like Benchmade, Buck, Lion etc aren’t finishing up their knives by hand, right?

AND, if they are heat treating I read somewhere its in big batches…how consistent is that?

I suppose I should ask the question directly to outfit like bench made to see what their process is, but I was hoping that somebody here might be familiar with it.

I do know that the process is completely different with the top knife makers like a Phil Wilson. I wanted to know how that differs with the mass manufacturers.
 
this is why people should buy knives from knife makers. Provided you're working with a diligent maker, you are going to end up with a a knife with secondary bevels that retain the as tempered hardness. My experience with production knives generally is that they'll hold an edge better after several sharpenings.
 
beendare said:
AND, if they are heat treating I read somewhere its in big batches…how consistent is that?
Click to expand...
Depends on the equipment they have, the steel they are using, and their quality assurance processes. If they are going to spend the money it can be very consistent, otherwise it might not be
 
The number one answer to controlling edge temper loss is grinding with a water spray/mist system. I believe most commercial knife grinding post-HT is done wet.
The second answer for limiting heat buildup is speed control of the equipment when grinding and sharpening the hardened edge.

A knife is ground and sharpened by applying a harder abrasive to the steel to remove it. This is a process of abrasion by friction.
The basic principle of physics is that friction removes the metal from the edge and friction causes heat. The heat can be dissipated by the mass of the blade to some degree, but the edge may be affected if the grinder speed is too fast to allow the heat to migrate and dissipate. This is controlled by the water spray and slower speeds.
 
When I sharpen, I wet the belt with a sponge and then sharpen. The belt is going slow enough that it's not flinging the water everywhere. The water pools up on the edge I am sharpening typically (edge up on a ceramic 120 grit belt). After the 120 grit belt to rough the bevel in and form the apex, I go to diamond stones 325/1200 Sharpnal and then strop.

On 99% of the steels I use, I grind 100% post Heat treat. I dip the blade in water frequently and at higher grits, I will wet the belt as well. S90V, with kitchen knives and wider blades, I will grind most of the bevels and go up to 400 grit or so on belts, heat treat, then do the final grinding. S90V hunters, I still grind post HT. I really want to get a mister setup soon! It's between that and the parts for a surface grinder for Christmas this year!
 
A mister system costs about what a good ceramic belt cost. You can get them as cheap as $10 on Amazon (Kool-Mist clone).
Add a few things that you probably already have ... air compressor and water supply bottle, plus some air hose ... and it will cool and lubricate your blades and belts amazingly.
It can be moved to the mill or other tools easily if you use a magnetic base.
I highly recommend the #77 lubricant/coolant solution that Kool-Mist sells. It's non-toxic, lubricates/cools well, and has a rust preventative. It costs a good bit but makes 33 gallons of lubricant misting solution. That will grind a lot of blades.
Wearing disposable 5-mil or 6-mil rubber gloves helps keep your fingers from getting too cold.
 
I need a compressor still and get the other components. I just dip the blade and wet the belt.
 
With a mister setup holding the blade the fingers never get warm the blade stays so cool. I LOVE my mister setup for grinding post HT.
 
So is it safe to assume the big mass produced outfits like Benchmade know what they are doing and don't wreck the temper of their blades?
 
As a Benchmade and Spyderco fan, I can tell you that I think Spyderco does a slightly better job with heat treatment altogether, but both companies do not "wreck the temper" of their blades while grinding/sharpening.
 
I'll put the use of a mister setup in a simile that my generation will understand.
"Switching to a mister system from grinding uncooled is like switching to a power mower after cutting grass with a manual reel mower." (You kids will have to look them up)
or
"Switching to a mist grinder is like switching from a dial phone to a cell phone." (Hmm, most of you kids will still have to look that up.)

OK kids, try this:
"Switching to a mister system is like switching from a dial-up modem to 802.1 Wi-Fi." (I had to look that one up.)
 
Lol. I guess the compressor will be on my Christmas List...Lol!
 
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