Why stop at 1"?

[3D Anvil]

Just wondering why (AFAIK) makers of guided sharpening systems restrict themselves to a maximum of 1" stone width. Why not use 2" wide stones, for example? Seems like using wider stones would speed up the sharpening process. Maybe it would cause problems at the tip and/or heel?

 

[FortyTwoBlades]

Mostly it's just not needed when bringing the stone to the blade rather than the blade to the stone. Unless you're dealing with a perfectly flat edge you wouldn't have more than a narrow contact surface anyhow, and it would cost more while being harder to hold.

 

[spoonrobot]

Wider stones magnify errors in the angle of attack between stone and edge. The wider the stone, the more susceptible the bevel is to off-angle grinding, where each side of the stone sits higher/lower and does not produce an even bevel.

Up to 1.5 inches seems to work ok, any wider and issues start cropping up. I experimented with diamond and ceramic plates a couple years ago for the exact reason you cited - thought it would be faster.

Think of it this way: For your 1" width of the stone, each 1° of off axis rotation moves the far side up/down about 0.017", for a 2" stone the error doubles to 0.034" - this is visually noticeable. 3" stones are essentially unusable without completely destroying the consistency of the bevel.

Part of this is how sharpening is different moving the stone vs. moving the knife. 3" wide benchstones work great, 6" wide bench stones are difficult and have the same issues as larger guided stones.

 

[Diemaker]

I had someone try my 2"x8" stones on a guided sharpener and they sent them back, said they were too big and cumbersome. How much width of your 1" stone do you tend to use? I have to try to use more than a 3/8" stripe down the center of mine.

 

[3D Anvil]

Wider stones magnify errors in the angle of attack between stone and edge. The wider the stone, the more susceptible the bevel is to off-angle grinding, where each side of the stone sits higher/lower and does not produce an even bevel.

Up to 1.5 inches seems to work ok, any wider and issues start cropping up. I experimented with diamond and ceramic plates a couple years ago for the exact reason you cited - thought it would be faster.

Think of it this way: For your 1" width of the stone, each 1° of off axis rotation moves the far side up/down about 0.017", for a 2" stone the error doubles to 0.034" - this is visually noticeable. 3" stones are essentially unusable without completely destroying the consistency of the bevel.

Part of this is how sharpening is different moving the stone vs. moving the knife. 3" wide benchstones work great, 6" wide bench stones are difficult and have the same issues as larger guided stones.

That makes sense. I figured it was something like that. I've got a 4x1.5" stone coming which I intended to use for free handing, but it occurred to me that it might work with my KME. I'm sure I'll give a try just to see what happens.

 

[3D Anvil]

I had someone try my 2"x8" stones on a guided sharpener and they sent them back, said they were too big and cumbersome. How much width of your 1" stone do you tend to use? I have to try to use more than a 3/8" stripe down the center of mine.

It does seem to be the case that the center of the stones gets the most load up, but I figured that was because it's really just the center touching along any kind of significant curvature. OTOH, I think most blades are 2/3 to 3/4 straight, or mostly so, a wider stone should be faster. Even on a bench stone, you tend to get darker areas where the belly/tip pass, even though it's a comparatively small part of the blade. I think the parts where the flats pass show less color because the metal is more evenly distributed.

 

[Mr.Wizard]

Even with one inch wide stones I wear the center faster than the edges causing me to lose some material when I lap them flat again. A two inch wide stone only makes the problem much worse on most knives. I have a few wide stones but they get very selective use.

 

[Bill3152]

The reality of it all is you don't need anything bigger than that even for free hand. Don't get me wrong I love my 8x3 inch bench stones. But I do pretty good with my folding dmt.

 

[Obsessed with Edges]

Some of the clamps used with simpler systems, like DMT's Aligner system, can be used with bench stones, with the clamp sliding on the tabletop alongside the stone. So, with those anyway, you do have the option of using a larger stone. I feel that's a better way to emulate what would otherwise be a standard freehand sharpening technique with bench stones and it's a decent way to train one's hands for that. Part of my own transition to freehand sharpening was spurred on by using the Aligner clamp with a bench stone, which helped me get the feel for that.

Beyond a certain size, using very large stones in the manner used on most guided-rig systems can get awkward, with the weight of the stones becoming a fatigue and control issue - especially if the stone is elevated & held above the blade. A momentary loss of control, of a larger & heavier stone held above the edge, can do some heavy damage to an edge. In that regard, smaller stones lend better finesse and a lighter touch with a smaller risk of damage by a momentary loss of control.

Large stones are best-suited for the heavy grinding and bevel-setting tasks, which may only need done once on most blades, after which the touch-up and maintenance sharpening can be done quite easily with smaller stones, where minimal metal removal is the norm.

 

[Spey]

I used a 2"x6" 220/600 double sided diamond plate on my E.P. for a couple years (along with other stones also). It took a few minutes to get used to ("awkward" as referenced by O.W.E. in Post #9), then I was Ok with it.

There are a number of situations where the wider stone will be a hinderance, like dealing with typical unsharpened portions just fwd of ricasso. Generally anything related to an edge that is curved opposite of a belly curve will be problematic - similar to comparing a 1" wide stone to a 1/2" wide stone.

Wider stone will displace pressure over a larger area. So for equal pressure, cuts less deep but wider (but only if in full contact with bevel). Does effective job of evening uneven bevels and exposing them, as contact area is much greater (2x vs a 1" Wide stone).

Generally, I would not recommend unless user has specific need. The only place I believe they benefit is on long straight sections, and when using same stone off the guide clamp (freehand, semi-freehand, etc.).

 

[3D Anvil]

Large stones are best-suited for the heavy grinding and bevel-setting tasks, which may only need done once on most blades, after which the touch-up and maintenance sharpening can be done quite easily with smaller stones, where minimal metal removal is the norm.

Agreed. My problem is that I reprofile a lot of blades, and usually ones with very wear-resistant steel. Doing that with a 1" stone is a huge PITA, which is why I find myself using my fixed angle system less and less.

 

[elasmonut]

Narrow stones deal with recurves better.

 

[Obsessed with Edges]

Agreed. My problem is that I reprofile a lot of blades, and usually ones with very wear-resistant steel. Doing that with a 1" stone is a huge PITA, which is why I find myself using my fixed angle system less and less.

That's a big part of what drove me to learning freehand. I started with a Lansky system and its 1/2" x 4" stones, and learned a lot in doing that. But any heavy grinding takes hours to finish with something that small, no matter how coarse the grit might be. At some later point, I tried a DMT Aligner guide clamp with a DMT 8" x 3" bench hone. Making that jump, all by itself, probably cut reprofiling times down to a small fraction of previous attempts, like maybe 30-45 minutes instead of 4 hours. That opened my eyes.

 

[777 Edge]

Agreed. My problem is that I reprofile a lot of blades, and usually ones with very wear-resistant steel. Doing that with a 1" stone is a huge PITA, which is why I find myself using my fixed angle system less and less.

Do yourself a favor and try out the Poltava 120 grit CBN metallic stone. It's a beast of a reprofiler on supersteels. Mine is worth its weight in gold to me.

Poltava Premium Metallic CBN Stone [6" x 1"]

Metallic CBN Sharpening Stones from Poltava Diamond Tools are used for sharpening knives using guided knife sharpeners (Hapstone, TSPROF, and other Edge Pro-compatible sharpening systems). CBN (Cubic Boron Nitride) is the second-hardest material after diamond. Metal bonded CBN stones utilize...

www.gritomatic.com

 

[3D Anvil]

That's a big part of what drove me to learning freehand. I started with a Lansky system and its 1/2" x 4" stones, and learned a lot in doing that. But any heavy grinding takes hours to finish with something that small, no matter how coarse the grit might be. At some later point, I tried a DMT Aligner guide clamp with a DMT 8" x 3" bench hone. Making that jump, all by itself, probably cut reprofiling times down to a small fraction of previous attempts, like maybe 30-45 minutes instead of 4 hours. That opened my eyes.

Yep, same revelation here. I use a KME with 1x4 stones, but even there it can take 2-4 hours to reprofile a blade with really hard steel. I'm using the Hapstone angle guide and continually working to improve my freehand sharpening.

 

[3D Anvil]

Do yourself a favour and try out the Poltava 120 grit CBN metallic stone. It's a beast of a reprofiler on supersteels. Mine is worth its weight in gold to me.

Poltava Premium Metallic CBN Stone [6" x 1"]

Metallic CBN Sharpening Stones from Poltava Diamond Tools are used for sharpening knives using guided knife sharpeners (Hapstone, TSPROF, and other Edge Pro-compatible sharpening systems). CBN (Cubic Boron Nitride) is the second-hardest material after diamond. Metal bonded CBN stones utilize...

www.gritomatic.com

Thanks for the rec! Unfortunately the 120 is out of stock at the moment, but I signed up for notifications when it comes back in stock. These are make in Ukraine, so, sadly, it could be quite a wait.