How are knives sharpened at the factory

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kent_michaels

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Does anyone know how ZT sharpens their knives at the factory? I’m assuming a belt or grinding wheel just for speed. I currently have a sharpmaker and can never quite seem to get knives back to that super sharp edge they come with from the factory. I’ve been considering getting a Ken Onion Worksharp to help get most of the work on re sharpening done quickly and then use the sharpmaker to refine the edge. Would that set up be able to closely mimic a factory edge?

ETA
I’m also considering the worksharp to get my kitchen knives sharp. Even with the CBN rods some of my kitchen knives are so dull that it’s an incredibly long process to bring one back to sharp.

Thanks
 
I'd be cautious about trying to replicate factory sharpening on belts, for fear of overheating the edge and ruining the temper. I get just as good results with an ultra-coarse DMT, then finishing the edge with fine (red) or ultra-fine (green) DMT hones.
 
A grinding wheel iirc. That was a while back, not sure if they have changed that with the new 20cv steel they use now at 62 hrc.

You should be using diamond stones and strops imho.

If your using cbn and still having issues... It could be your sharpening technique.

The work sharp abrasives aren't that hard for pm steel sharpening imho. Also they will scratch up your blades and blunt your tips without practicing to avoid that. Also instead of a v grind, they will be convex. Many have used it without issues and blade grinding attachment can help. I've seen some folks use it for 10v among many other powdered steel types.
 
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It would be really interesting to know what kind of abrasive belts that makers are using.

Pretty sure they have to use diamonds or else all knives shipped would have carbide tear out.
Right?
 
willc said:
It would be really interesting to know what kind of abrasive belts that makers are using.

Pretty sure they have to use diamonds or else all knives shipped would have carbide tear out.
Right?
Click to expand...
From the threads discussed here, Using coarse enough belts should just plow through the micron size carbides. Generally oem's use 400 - 600 grit max.

The tear out likely happens at finer grits. Generally factory grinds have to worry about over heating the edge imho.
 
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Mo2 said:
A grinding wheel iirc. That was a while back, not sure if they have changed that with the new 20cv steel they use now at 62 hrc.

You should be using diamond stones and strops imho.

If your using cbn and still having issues... It could be your sharpening technique.

The work sharp abrasives aren't that hard for pm steel sharpening imho. Also they will scratch up your blades and blunt your tips without practicing to avoid that. Also instead of a v grind, they will be convex. Many have used it without issues and blade grinding attachment can help. I've seen some folks use it for 10v among many other powdered steel types.
Click to expand...


My sharpening technique is okay. The kitchen knives that haven’t been sharpened in 10 years though take a lot longer than I’d like on the CBN rods. Once a knife has decent working edge I can get it shaving sharp with the sharpmaker. I’m curious if the KOWS with the blade grinding attachment could get the bulk of the initial sharpening done in a handful of passes versus countless passes on the sharpmaker.
 
I don't know what the factories use, but factory edges come in all shapes and sizes. The factory doesn't replicate what the factory does.

Before you start removing a whole lot more metal a whole lot faster, you might want to noodle out your edge angles and the angles of the stone. If you're not getting your knives sharp with a Sharpmaker, your geometry is off. Fix that.

You want the angle of the stone to match the angle of the edge, otherwise you can end up sharpening for a long time without doing much good.

If you want to be able to resharpen fast, establish a 30 degree inclusive back bevel and a 40 degree inclusive microbevel (or edge). Once you establish those edge angles, you can use your Sharpmaker to its most efficient and effective potential.
 
Twindog said:
I don't know what the factories use, but factory edges come in all shapes and sizes. The factory doesn't replicate what the factory does.

Before you start removing a whole lot more metal a whole lot faster, you might want to noodle out your edge angles and the angles of the stone. If you're not getting your knives sharp with a Sharpmaker, your geometry is off. Fix that.

You want the angle of the stone to match the angle of the edge, otherwise you can end up sharpening for a long time without doing much good.

If you want to be able to resharpen fast, establish a 30 degree inclusive back bevel and a 40 degree inclusive microbevel (or edge). Once you establish those edge angles, you can use your Sharpmaker to its most efficient and effective potential.
Click to expand...


I guess I’ve been lucky with my previous knives and never had to set the back bevel. I just checked it on my 0452 that I was having trouble getting as sharp as I’d like. The right side was pretty much dead on 30 the left side was easily well over 40. Took some time and got the left side close but not perfect to 30 (ran out of time) and was able to get it much sharper with a few minutes on the Med and fine rods. Thanks! Next week when I have some time I still need to get that left side thinned out some more.
 
I know I might ne a little off here, and I'm guessing, but from what I have seen on some factory knives by popular brands :
First you stop off on the way to work to the liquor store and pick up a fifth of scotch.
Have a nice breakfast in the parking lot on said purchase.
Clock in.
Cross eyes firmly.
And start in on the knives.
Under no circumstance try the edges on your finger nail to test for wire edge or actual level of sharpness.
In the after noon find the kid who sweeps up and empties trash bins and turn the back log over to him.
Take a nice little nap until it is time to clock out and go home.

Sharpening knives in a factory is brutally difficult and highly skilled work that can only be properly done on high priced knives . . . right ?
I do know the Cold Steel Kitchen Classic paring knife that sells at a retail price of ~$11 is symmetrically perfect and litterally hair whittling out of the package EVERY TIME ! ! !
I have several.
Those German dudes . . .
I don't know how they do it but some of the other knife companies have some SERIOUS catching up to do.

PS : it's almost like actually cutting something with their product is the furthest thing from their imagination. Don't make it sharp some one might cut their finger.
 
I just checked a lot of my ZT’s, almost all are collectors for me and all but 1 have very uneven bevels. I never really check that on my knives but I’m surprised as expensive as ZT’s are they’d have such uneven bevels. Oh well I still love everything else about them.

ETA
Funny you say that about cold steel every cold steel I’ve ever had has literally been scary sharp out of the box.
 
I don't know a lot about factory sharpening; just what I've read. ...and what I've read is that most use a belt sander at 220 to 320 grit to establish the bevel. Then, once a burr is formed, they use a buffing wheel (I've heard that cotton is common) to buff off the burr.

If you examine a factory edge, you'll see pretty coarse grinding marks on the edge bevel. ...and if you look really closely, you'll almost always see a very shiny micro bevel (a teeny tiny one) at the very edge of the edge. That's from the buffing wheel. So the factory edges are a "polished toothy" edge in most cases.

I bought a WSKO precisely for sharpening abused blades that were dull, dull, dull, and then dull some more. This sped up my process a LOT, but I'm still a bit slow with a really dull blade. It might take me a solid 10 minutes (or more?) to take a knife from butter dull to where it should be. I'm talking about blades that haven't been sharpened for 20 years, so in many cases, I'm actually re-grinding the edge bevels in the process of sharpening them.

The WSKO is a useful tool for sure. As long as you recognize it for what it is.

Brian.
 
In that second video that cbwx34 linked to, the blade is all over that grinding wheel. He tends to sharpen the right edge lower on the grinding wheel than the left edge, so he's going to have uneven edge bevels.

It still amazes me that the sharpening process at the factory isn't automated.
 
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kent_michaels said:
Funny you say that about cold steel every cold steel I’ve ever had has literally been scary sharp out of the box.
Click to expand...
Now if they could only build a sheath that doesn't dull the edge in a day on their fixed blades they could win the title of : Real Knife Company . . . rather than adult toy maker.

That didn't come out exactly as intended but it's funnier that way so I left it.
I'm still battling the sheath on my last CS; danged if I'm not going to come up with something I can fit between the layers to protect my carefully sharpened edges . . .
CURSE YOU COLD STEEL YOU EVIL VILLAINS !
 
kent_michaels said:
Does anyone know how ZT sharpens their knives at the factory? I’m assuming a belt or grinding wheel just for speed. I currently have a sharpmaker and can never quite seem to get knives back to that super sharp edge they come with from the factory. I’ve been considering getting a Ken Onion Worksharp to help get most of the work on re sharpening done quickly and then use the sharpmaker to refine the edge. Would that set up be able to closely mimic a factory edge?

ETA
I’m also considering the worksharp to get my kitchen knives sharp. Even with the CBN rods some of my kitchen knives are so dull that it’s an incredibly long process to bring one back to sharp.

Thanks
Click to expand...

Thought I remembered something, checked that it’s still true, ZT and Zershaw will sharpen your knifes for free. Walk in with up to two at a time or mail them into thier factory. Have not done that myself and folks into sharpening won’t, but be it’s still there.
 
When knives are real dull, (like my mother inlaws) or need a new bevel, I start with a water wheel grinder.
 
I am impressed by factory edges. The scratch pattern on edges of supermarket kitchen knives, Ganzo, Spyderco, Victorinox multitools, Leatherman, etc looks coarse, maybe 300 grit or less, but the edges are scary sharp. I can only get to scary sharp after refining the scratch pattern.

Factory edges never come polished. They are a mystery and best proof that edges don't need a fine scratch pattern, let alone polished finish, to be scary sharp. Of course, under the microscope one can see that the apex is microstropped, probably through a stropping wheel.

Anyway i would love to see a detailed factory video showing how Spydie edges are finished off. We know that they use wheels. But now we want to see the wheels :thumbsup:
 
kent_michaels said:
I just checked a lot of my ZT’s, almost all are collectors for me and all but 1 have very uneven bevels. I never really check that on my knives but I’m surprised as expensive as ZT’s are they’d have such uneven bevels. Oh well I still love everything else about them.

ETA
Funny you say that about cold steel every cold steel I’ve ever had has literally been scary sharp out of the box.
Click to expand...

I've sharpened enough ZTs to second that opinion. Also most come about 50° inclusive, which is going to cause problems for a Sharpmaker.

At a guess I'd expect most shops use a ceramic belt at 320 grit or so and buff it out on a paper wheel or other firm wheel. Some might use a leather or cork belt. Some shops for sure use a grindwheel as you can see the microhollow when you sharpen them the first time.
 
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