need help please with edge pro sharpening/stropping

[hemi1300]

sorry if this is in the wrong section, haven't been on in a while. Anyway, currently have the edge pro with shapton glass stones, numerous strops, and can get my edges blazingly sharp on any of my knives (benchmade's and spyderco's), typically at about a 23-25 degree angle on each side. My problem is, after getting them hair shaving/paper slicing sharpness, after one day of use cutting a little cardboard/paper, and numerous items at work, the edge has already lost it's paper slicing sharpness. Typically though, just a few seconds back on the strop will bring the edge right back to razor sharpness, rarely do i have to hit it with the stone's again. Can get them just as sharp as spyderco or benchmade factory edge's, but the factory edge from these knives seem to last a while before dulling even the slightest, where as my edge's on the edge pro seem to lose their sharpness after a handful of slices through cardboard. Any sharpening tips would be greatly appreciated

 

[Inazone]

Here is a thread specifically about Spyderco and Benchmade sharpening from another forum:

http://edcforums.com/threads/benchmade-and-spyderco-factory-edges.49701/


I don't have personal experience with either brand, but your angles sound a bit aggressive.

 

[EChoil]

I'd say it's your angles.

 

[PURPLEDC]

I think the real issue here is the edge you are putting on your knife. A really fine polished edge looks great, and will shave hair and push cut paper really well but its not the best suited for cutting cardboard. Factory edges have micro serrations that help facilitate slicing. When you mirror polish and edge and use a strop with jewelers rouge you take the edge down so fine and polished that there is no longer any little teeth to the edge. Polished edges are great for opening letters, push cutting paper and cutting tape on boxes. But if you plan on actually cutting cardboard and or other heavier duty tasks I actually would recommend keeping your edge on the toothy side. There are many variables that will give you better or worse results such as the type of steel, the andle in which you are sharpening among other things. The factory edge may looks a few of those teeth during use but in general the edge will still perform cardboard cutting tasks even if a few of those teeth get broken or worn down. A polished edge is so fine that I find it goes quicker yet comes back much easier too. Try it both ways. but in the case with a toothy edge I touch up on a ceramic, and on a polished edge I use the strop.

 

[Obsessed with Edges]

sorry if this is in the wrong section, haven't been on in a while. Anyway, currently have the edge pro with shapton glass stones, numerous strops, and can get my edges blazingly sharp on any of my knives (benchmade's and spyderco's), typically at about a 23-25 degree angle on each side. My problem is, after getting them hair shaving/paper slicing sharpness, after one day of use cutting a little cardboard/paper, and numerous items at work, the edge has already lost it's paper slicing sharpness. Typically though, just a few seconds back on the strop will bring the edge right back to razor sharpness, rarely do i have to hit it with the stone's again. Can get them just as sharp as spyderco or benchmade factory edge's, but the factory edge from these knives seem to last a while before dulling even the slightest, where as my edge's on the edge pro seem to lose their sharpness after a handful of slices through cardboard. Any sharpening tips would be greatly appreciated

I'd say it's your angles.

This.^

23-25° per side (46°-50° inclusive) is pretty thick for any type of cutting. At such angles, only a perfectly-crisp apex is making it work. Cardboard is very abrasive, and will kill it fast. When the apex isn't crisp anymore, the underlying geometry is all that's left, and such a wide edge won't slice well with a dull apex.

Thinner geometry, at or below 40° inclusive (20°/side), tolerates the loss of a perfectly-crisp apex a little better. A BIG improvement in cutting will be seen at 30° inclusive (15°/side) or lower; paper-cutting gets a lot easier at such geometry, and the edge will cut better at everything else as well, polished or not. The thin geometry is what makes the bigger difference, more so than the edge finish.


David

 

[hemi1300]

Thank you for the advice. So for a toothier edge on the edge pro, what grit stone would u use, 220? Possible to still get it sharp enough with a 220 stone to effortlessly slice paper? And should I use the strop after or just leave it after the stone?

 

[singularity35]

Try 600 grit at 15 dps.

 

[hemi1300]

Re-sharpened my benchmade 943 tonight with just strictly a 220 stone at about 24 degree per side. Got it pretty sharp to slice paper with just the stone, so I will see if it holds up longer. Reason I have been going around 22-25 degree per side is bc that was about the angle of the factory edge on my edge pro using the sharpie trick. From my understanding, wouldn't a 15 degree edge dull down much quicker, and be much more brittle, than a 20-25 degree edge? Using my angle cube, my benchmades have always been around 25 per side and spyderco's normally 20-22 per side

 

[Obsessed with Edges]

Re-sharpened my benchmade 943 tonight with just strictly a 220 stone at about 24 degree per side. Got it pretty sharp to slice paper with just the stone, so I will see if it holds up longer. Reason I have been going around 22-25 degree per side is bc that was about the angle of the factory edge on my edge pro using the sharpie trick. From my understanding, wouldn't a 15 degree edge dull down much quicker, and be much more brittle, than a 20-25 degree edge? Using my angle cube, my benchmades have always been around 25 per side and spyderco's normally 20-22 per side

No modern steel with decent heat treat should be at any risk of damage at 30° inclusive (15° per side), and many or most modern steels can usually hold up well down to at least 25° inclusive (12.5° per side). I wouldn't worry at all about brittleness or edge-rolling at these edge angles.

If the factory edge was at >22° per side or higher, I'd bet that was in error (from the factory). Most modern mfr's will usually claim to hit 20° per side or lower, though factory edges are still finished by hand most of the time, and will sometimes be notoriously wide in angle.

What steel is your BM 943, BTW?


David

 

[singularity35]

I've found my 20 dps knives dull much faster than the same knife sharpened at 15 dps.

 

[Obsessed with Edges]

I've found my 20 dps knives dull much faster than the same knife sharpened at 15 dps.

Me too. :thumbup:

That's what hammered the point home to me, that the crisp apex is the only thing that's working when the geometry is very wide. Then the edge becomes functionally 'dull' (nearly useless) when the crisp apex is gone, and that usually doesn't take long. At thinner edge angles, the edge will still be thinner even when it dulls a bit, so it retains at least some of it's usefulness, even when the apex isn't as crisp.

I've mentioned it before, but Buck Knives also figured this out a while back (verified by CATRA sharpness testing), and they've since changed their target spec for their knives to aim for 26°-32° inclusive, when their previous spec used to be much wider.


David

 

[singularity35]

Me too. :thumbup:

That's what hammered the point home to me, that the crisp apex is the only thing that's working when the geometry is very wide. Then the edge becomes functionally 'dull' (nearly useless) when the crisp apex is gone, and that usually doesn't take long. At thinner edge angles, the edge will still be thinner even when it dulls a bit, so it retains at least some of it's usefulness, even when the apex isn't as crisp.

I've mentioned it before, but Buck Knives also figured this out a while back (verified by CATRA sharpness testing), and they've since changed their target spec for their knives to aim for 26°-32° inclusive, when their previous spec used to be much wider.


David

I was going to try to explain what I thought was happening but my effort wasn't to comprehensible and I decided to forego posting. Your explanation is much better.

And second is, that there is a huge difference in cutting performance so no downside.

 

[loonybin]

sorry if this is in the wrong section, haven't been on in a while. Anyway, currently have the edge pro with shapton glass stones, numerous strops, and can get my edges blazingly sharp on any of my knives (benchmade's and spyderco's), typically at about a 23-25 degree angle on each side. My problem is, after getting them hair shaving/paper slicing sharpness, after one day of use cutting a little cardboard/paper, and numerous items at work, the edge has already lost it's paper slicing sharpness. Typically though, just a few seconds back on the strop will bring the edge right back to razor sharpness, rarely do i have to hit it with the stone's again. Can get them just as sharp as spyderco or benchmade factory edge's, but the factory edge from these knives seem to last a while before dulling even the slightest, where as my edge's on the edge pro seem to lose their sharpness after a handful of slices through cardboard. Any sharpening tips would be greatly appreciated

Far too obtuse of an edge. Go thinner. For my harder use knives (Rift, Contego in M390, Presidio in CPM-M4) I go 17º per side. For my indoor/office/dress knives that will mostly be slicing paper/cardboard/etc., I go 15º per side

Re-sharpened my benchmade 943 tonight with just strictly a 220 stone at about 24 degree per side. Got it pretty sharp to slice paper with just the stone, so I will see if it holds up longer. Reason I have been going around 22-25 degree per side is bc that was about the angle of the factory edge on my edge pro using the sharpie trick.

Benchmade hand sharpens their knives at the factory, so they will be a bit more obtuse. The angles from the factory are not the optimum angles for the steel used. 154CM, s30v, D2, M390, CPM-M4 work better at thinner angles if all you're doing is slicing

From my understanding, wouldn't a 15 degree edge dull down much quicker, and be much more brittle, than a 20-25 degree edge? Using my angle cube, my benchmades have always been around 25 per side and spyderco's normally 20-22 per side

They will not dull quicker, because they are thinner behind the edge, thus their cutting ability is better to start with. If all you're doing is slicing and not applying lateral force, then the thinner angle is better. If it's a hard use outdoor knife that you're going to be batoning and prying wood with, then you'll want a more obtuse edge to withstand the lateral stress.