(Hopefully) simple question

[pcb01]

I've been warned by a couple of folks not to do too many passes on a pasted CrOx (0.5) paddle strop. They suggest doing no more than 10-20. They're a little hazy on why. What has been known to happen with excessive use of this? Thanks.

 

[gugi]

the worst that can happen is either dull or overhoned razor.

check mparker's posts - he hasn't found any adverse effects from many passes, but there are from excessive paste or sagging of the strop.
and there are few people if any to actually investigate stropping in so much detail as he has.

of course it's probably best to ask for the reasons the people who give you a particular advice since they would have the experience that drives it.

 

[Chimensch]

Honing (edge leading) carries the metal removed behind the edge. Stropping (edge trailing) carries the metal removed in front of the edge. When stropping with an abrasive you have a greater tendency to create a wire edge, or burr, that will easily break-off. There is a simple test for a wire edge that you can use to test your blade after stropping with chromium oxide. Try sawing terrycloth. A good edge will not cut terrycloth but a wire edge will rip it up.

 

[mparker762]

When stropping with an abrasive you have a greater tendency to create a wire edge, or burr, that will easily break-off.

This is backwards.

Prof. Verhoeven's looked at this in his paper "Knife Sharpening Experiments", where he examined edges at up to 10,000x using a scanning electron microscope. What he found was that honing edge-leading on a stone caused a wire edge or burr in every single case. Honing edge-trailing on a pasted paddle using just about any abrasive (including chrome oxide) was the most effective method of removing this wire or burr, and (controversially) that stropping on a plain leather strop did not remove burrs.

Also, one of the time-honored ways on these forums to get rid of a wire edge is to backhone (edge-trailing) on your stone for a few laps, and this would hardly work if edge-trailing honing actually caused burrs.

 

[Thebigspendur]

In the end its the old story of less is more. You do the least number of passes you need to do the get the edge the way you want it, Doing more just takes more metal off the razor and you can wind up with too fragil an edge depending on what media you are using.

 

[sapito318]

in the end its the old story of less is more. You do the least number of passes you need to do the get the edge the way you want it, doing more just takes more metal off the razor and you can wind up with too fragil an edge depending on what media you are using.

+1

 

[Chimensch]

This is backwards.

Prof. Verhoeven's looked at this in his paper "Knife Sharpening Experiments", where he examined edges at up to 10,000x using a scanning electron microscope. What he found was that honing edge-leading on a stone caused a wire edge or burr in every single case. Honing edge-trailing on a pasted paddle using just about any abrasive (including chrome oxide) was the most effective method of removing this wire or burr, and (controversially) that stropping on a plain leather strop did not remove burrs.

Also, one of the time-honored ways on these forums to get rid of a wire edge is to backhone (edge-trailing) on your stone for a few laps, and this would hardly work if edge-trailing honing actually caused burrs.

Thanks, I'll have to go back and reread it.

 

[Chimensch]

This is backwards.

Prof. Verhoeven's looked at this in his paper "Knife Sharpening Experiments", where he examined edges at up to 10,000x using a scanning electron microscope. What he found was that honing edge-leading on a stone caused a wire edge or burr in every single case. Honing edge-trailing on a pasted paddle using just about any abrasive (including chrome oxide) was the most effective method of removing this wire or burr, and (controversially) that stropping on a plain leather strop did not remove burrs.

Also, one of the time-honored ways on these forums to get rid of a wire edge is to backhone (edge-trailing) on your stone for a few laps, and this would hardly work if edge-trailing honing actually caused burrs.

I went back and read the Verhoeven article again and we are both half-wrong and half-right. On page 22 and 23, Verhoeven says that edge-leading honing does create burrs but that edge-trailing creates bigger burrs. I don't know how this squares with your experience of back-honing. In retrospect, I got the idea that stropping with chromium oxide may extend a thin edge from Bart and not Verhoeven.

 

[mparker762]

I went back and read the Verhoeven article again and we are both half-wrong and half-right. On page 22 and 23, Verhoeven says that edge-leading honing does create burrs but that edge-trailing creates bigger burrs. I don't know how this squares with your experience of back-honing. In retrospect, I got the idea that stropping with chromium oxide may extend a thin edge from Bart and not Verhoeven.

I went through that section of the Verhoeven paper and you're right. My guess is the reason that backhoning on a stone removes the burrs from forward honing is simply that the different stroke direction stresses the burr differently and causes it to break off.

It turns out Verhoeven was able to create burrs using pastes, but only by using abrasive felt or cloth wheels on the Tormek machine; I had mostly skimmed those sections since they're not terribly useful for razors (as the micrographs show). He wasn't able to create burrs using manual stropping on pasted strops.

 

[leighton]

I went through that section of the Verhoeven paper and you're right. My guess is the reason that backhoning on a stone removes the burrs from forward honing is simply that the different stroke direction stresses the burr differently and causes it to break off.

I agree. It makes sense in my head and works in real life. Also, the wire edge leading backwards also makes sense, but we all know wire edges can be created through edge leading honing as well.

I don't see how it would be possible to create a wire edge using a pasted strop in theory. All I can foresee is over "stropping" the edge so you have more of an appleseed edge that needs to be taken back to the hones to recreate a more acute angle. Due to the nature of the substrate the paste is placed upon.

 

[Sticky]

I've been warned by a couple of folks not to do too many passes on a pasted CrOx (0.5) paddle strop. They suggest doing no more than 10-20. They're a little hazy on why. What has been known to happen with excessive use of this? Thanks.

10 laps on CrOx are often enough to refresh the edge. More laps = more convex bevels/edge (one reason many prefer CrOx on a paddle vs. a strop). The more often the chrome is used, the sooner you'll need a hone.