How do the big companies put edges on their knives?

20yard

20yard

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Some are way better than others, but I'm curious how the bigger production companies put on their factory edges. I imagine a lot of thought goes into how to put on a good edge in a manner that is efficient relative to the rest of the production work flow. Probably a big factor when churning out thousands of knives.

Some of my recent Spyderco purchases, with their remarkably good factory edges compared to others, is what caused me to start thinking about this.

Would appreciate any insight.
 
Sanding belts. The fast moving belts heat the edge when they sharpen the blades. Many feel that you don't get to the "good steel" until you sharpen a couple times to get rid of the tempered steel.
 
Arathol said:
Robots.......
Go to about 5 minutes in....
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That's what I was wondering mostly about. Automated vs. hand sharpening. Very interesting!

And WOW with those pellets at 6:55. It's crazy that entire hopper of pellets was presumably extracted just from their waste water. That's a lot of grinding!
 
 
Depends on the age of the factory too. Some of the older European factories use people sitting at grinding and polishing wheel stations, sometimes a more modern belt grinder will sneak it there too. Most of the American factories were like that too, up until recently, say the last 10-15 years or so.

Case, Buck, GEC, Puma, most of the NE US firms are some combo of wheel, belt, buffer.

Benchmade was belts, not sure if it is still.
 
jbmonkey said:
last I heard and seen in videos.....Buck still does theirs by hand on belt sanders.
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And yet their edges are excellent. How interesting. There is a lesson in all this, which is that belt sharpened edges can be better than a lot of people might think, as long as the craftsman making it understands how to grind.
 
I'm kind of new here so sorry if these are dumb questions, but is there anything bad about belt sanding/grinding except the heat issue and potential for altering the temper? (Ignoring the possibility of an amateur messing up the geometry with a powered grinder...)

Also, does using a water mist/spray while belt grinding pretty much "solve" this issue (so long as you don't go crazy bearing down on the blade)? I realize that at the very apex, you don't have much metal for a heat sink, so it heats up fast...

Lastly, I've read the data sheets on a few of the "super" steels (specifically, Carpenter Maxamet, CPM Cru-Wear, M4 and 3V) and see that they (or at least some of them) have some very high tempering temperatures ... so is overheating when sharpening on a belt sander still a concern for those? Also, are there even belts available that have hard enough abrasives to grind the high-carbide steels without messing them up? What abrasives would be used for this? I don't think I've ever seen diamond sanding belts...

I'm hoping some of the knifemakers and other experts here will weigh in on these...TIA for any insights.
 
Cementite said:
I'm kind of new here so sorry if these are dumb questions, but is there anything bad about belt sanding/grinding except the heat issue and potential for altering the temper? (Ignoring the possibility of an amateur messing up the geometry with a powered grinder...)

Also, does using a water mist/spray while belt grinding pretty much "solve" this issue (so long as you don't go crazy bearing down on the blade)? I realize that at the very apex, you don't have much metal for a heat sink, so it heats up fast...

Lastly, I've read the data sheets on a few of the "super" steels (specifically, Carpenter Maxamet, CPM Cru-Wear, M4 and 3V) and see that they (or at least some of them) have some very high tempering temperatures ... so is overheating when sharpening on a belt sander still a concern for those? Also, are there even belts available that have hard enough abrasives to grind the high-carbide steels without messing them up? What abrasives would be used for this? I don't think I've ever seen diamond sanding belts...

I'm hoping some of the knifemakers and other experts here will weigh in on these...TIA for any insights.
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Hard, high alloy steels are usually ground with ceramic belts.
High speed, high pressure, fast passes, Wet.

I like to do my final edges on bench stones.
Some of the process includes diamonds

Yes some steels (high speed steels) M2 and M4 are a bit more forgiving about temper
 
Randall knives puts their final edge on using a stone, but they’re not a big company.
 
Cementite said:
I'm kind of new here so sorry if these are dumb questions, but is there anything bad about belt sanding/grinding except the heat issue and potential for altering the temper? (Ignoring the possibility of an amateur messing up the geometry with a powered grinder...)

Also, does using a water mist/spray while belt grinding pretty much "solve" this issue (so long as you don't go crazy bearing down on the blade)? I realize that at the very apex, you don't have much metal for a heat sink, so it heats up fast...

Lastly, I've read the data sheets on a few of the "super" steels (specifically, Carpenter Maxamet, CPM Cru-Wear, M4 and 3V) and see that they (or at least some of them) have some very high tempering temperatures ... so is overheating when sharpening on a belt sander still a concern for those? Also, are there even belts available that have hard enough abrasives to grind the high-carbide steels without messing them up? What abrasives would be used for this? I don't think I've ever seen diamond sanding belts...

I'm hoping some of the knifemakers and other experts here will weigh in on these...TIA for any insights.
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It is mainly the affect on the temper.

I use to have access to Messerklingen und Stahl by R. Landes that discuss this in detail but Larrin Larrin book is also a good reference with some images on page 106 if you are interested.

Water or cooling media makes a difference in grinding.
 
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I've often wondered how Cold Steel fine serrations are made . Usually very well machined , IMO . Better than their PE .
 
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Some companies seem like they drug the blade across the sidewalk in front of the factory before they put it in the box. 🤣
 
Cementite said:
I'm kind of new here so sorry if these are dumb questions, but is there anything bad about belt sanding/grinding except the heat issue and potential for altering the temper? (Ignoring the possibility of an amateur messing up the geometry with a powered grinder...)

Also, does using a water mist/spray while belt grinding pretty much "solve" this issue (so long as you don't go crazy bearing down on the blade)? I realize that at the very apex, you don't have much metal for a heat sink, so it heats up fast...
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This is exactly why its been said many times that you can't get a decent edge on a new knife until you remove the factory edge and expose steel that hasn't been affected by the factory grinding process.
 
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