Can stropping dull the edge?

[grepper]

Say you started stropping by laying the knife flat on the wheel so the edge was nowhere near the wheel.  What would happen?  The side of the knife would become polished, but of course it would have no effect on the edge at all.

If the blade was slowly rotated towards the edge, the polished part would get closer and closer to the edge. But it still would have no effect on the edge performance as the cutting edge is still untouched.

At some point the angle of the blade on the honing wheel is the same as the angle it was sharpened to and the strop and honing compound touch the edge.  This will further grind the edge and work whatever incredibly thin wire edge still exists on the blade.  Because the honing compound is actually a steel cutting abrasive, it will further sharpen the edge, as well as smooth areas higher on the bevel that were previously ground with a coarser abrasive.

But what happens if the blade is further rotated so that, even on a microscopic scale, the blade starts to scrape perpendicularly to the wheel?  What happens is the extremely thin edge that makes the blade sharp, bends over in the direction of the rotation of the wheel.  Tiny portions of the edge are torn away.  The abrasives in the honing compound form micro scratching on the bent surfaces of the edge, and essentially start to from a new bevel angle.  The edge becomes duller.  Carried further and eventually you get a free butter knife.

It seems to me, the only possible way stropping can negatively impact edge performance, (unless your idea of performance is a "toothy" edge), is if the edge is stropped at a greater angle than the sharpened angle, or if stropping at a coarser grit than the original sharpening, as the dude who wrote the Canadian article documented in amazing detail. 

[Rob]

all makes sense....anybody reading this should also see the thread about abrasives and edge quality

[Jeff Farris]

Isn't this what I've been saying for something like 20 years or so? 

[Herman Trivilino]

Yes, it is.  You've also made us aware of the fact that, in addition to the angle, we also have to pay attention to the position of the edge on the stropping wheel.

[mike40]

One thing that occurred to me today while honing my chisel was that the stropping wheel is considerably smaller in diameter than the grinding wheel (when new), and I wonder what, if any, effect that would have on stropping, at least in theory.

[Jeff Farris]

One thing that occurred to me today while honing my chisel was that the stropping wheel is considerably smaller in diameter than the grinding wheel (when new), and I wonder what, if any, effect that would have on stropping, at least in theory.

In theory, if you use a jig, set it at exactly the same angle, and use no down pressure, the honing wheel will polish the middle of the bevel, missing the edge and the heel of the bevel. In practice, the leather has enough give to cover the entire bevel with just a bit of down pressure.

[mike40]

Thanks Jeff. I just completed my second chisel. It is a Swedish chisel made from chrome vanadium steel. I don't know the Rockwell hardness and with all the different mixes I can't even guess it. I can say that this chisel is a lot harder steel than the first chisel I sharpened on the Tormek.  It took  awhile to get the bevel completed at 220, but no complaints as I only have to do this drastic a grind once. The 1000 grind went quickly. I did the stropping freehand. It turned out great. The chisel easily passed the paper test. Now I just have 6 more of these chisels to sharpen. They are my 'new' chisels I bought 14 years ago.

The only problem I encountered was getting a square edge, It seemed to take forever, but I could hear the wheel grinding on the high side and silent on the other as I passed the chisel over the stone, so I just kept at it until it was square. While that was going on I was checking frequently with my try square, but at first I was registering off the opposite side of the chisel from where it was registering in the jig. When I realized that, It made me wonder if that wasn't part of Kens problem with getting a square edge. Maybe the two sides of his chisel aren't parallel. Just a thought Ken.

Here are some photo's of the result, please don't applaud, I know this is old stuff to you. I just want to demonstrate that I am learning from you guys. The 2nd pic is the back of the chisel blade reflecting my hacksaw hanging on the wall behind me. The third photo is to show you how the problem with water spillage was dealt with. This was my wife's  idea. It is a car floor mat which features upturned edges all around. It was relatively cheap and it works like a charm. Wife 1, Mike 0.


 

[Rob]

very creative Mike.....I like the reflection in the 2nd shot.....demonstrates the mirror finish by analogy...you arty type you :-)

[Ken S]

A lot of good information and some humor here.  Nice well thought through description of stropping.

Interesting observation of our "new" tools, Mike.  It reminds me of "New College", the theology school at the University of Edinborough.  It was founded around the fifteenth century.

Good point about some chisels not being ground parallel.  For chisels where being square is important, a simple check of parallelism with calipers would solve the mystery.  If the edge to edge dimension is consistent from the bevel back, the chisel is ground parallel.

Nice idea using the car mat to catch the water spill.  Some spillage seems inevitable.  By the way, when drying off after sharpening, I life up the Tormek and dry off the revolving base unit.  By doing so, I'll never know if leaving it wet might cause any rust inside. i also let the unit run for a minute with the tray removed to let centrifugal force wick any moisture toward the outside of the stone.  I have no idea if there is any scientific basis for this; it just seems to make sense.

Ken

[mike40]

Thanks Rob and Ken.Strange that you should mention 'New College' in Edinburgh. That is where my Great grandfather attended university before emigrating to America to become a minister in South Dakota. My grandmother had his leather-bound book of sermons. Handwritten in a beautiful script. I only saw it once when I was young, but the penmanship left an everlasting impression. I googled the college and it said it was founded in 1846, but maybe went under a different name before that. Here's the link: http://en.wikipedia.org/wiki/New_College,_Edinburgh. Sorry to get off the subject here. Thanks for the tips about drying things up Ken. I haven't got the revolving base, but I find that just spinning the machine with the mat is so easy, that I don't think I will needing one.

[Rob]

I thought you got the revolving base with a new machine purchase these days??  Perhaps that's a dealer specific offer I've seen here.

[Jeff Farris]

Mike,

I love your car mat idea. I've advocated cafeteria trays for a long time, but they don't cover the area that your mat does, and they can be hard for an honest person to come by!

[mike40]

Rob. I've seen ads for from dealers with the Tormek at different prices for different package deals that include more or less accessories. Mine didn't come with the revolving base . I was planning to get one before I got the mat, but I don't see any advantage now.

Yes Jeff, I think my wife had a brilliant idea with that mat. The left side of the mat as seen in the photo is shaped a bit like a spout, so it is easy to poor off spill water, but of course you have to lift the machine off with the matt to do it. I was originally looking for a lid from a large plastic storage box, but I found that the didn't have very even bottoms because they have to be profiled to give sufficient strength.

[Rob]

I find lifting the Tormek up and round a bit of a pain so I'm going to get one of those bases myself.  I have mine on an old towel that is folded about four times.  It doubles as a wiping substrate after honing or when I want water off the edge for inspection.