Stropping with compounds vs sharpening

The closest one can get IMHO is through the use of a sharpening board - an oak or other open grain hardwood sprinkled with relatively pure silicon oxide. These were common in a lot of places where there was ample abrasives, but not bound in good quality natural stones.

The outcome is not bad to very good depending on how well you can manage the variables, but a stones is going to be way better for sharpening. The advantage to "stropping" is the action by its nature is unlikely to create a burr and likely to eliminate one. The downside is you lose some precision and are likely to dub the edge into a much larger angle than intended

 

Yup, stones create, strops enhance, it's just that simple.

 

So what you guys are saying is I did indeed screw up my edge on the stones and can't blame my careless stropping.

Sigh...

 

I'm not a pro and relatively new to all of this. I now use wood as a strop more often than leather. I can't say it works better but I get good results. My brain says wood should keep a keener edge because it deforms less than leather. But there could be other things going on with leather I'm not aware of.

I'll take your word for it. In my limited testing, my stropped edges all cut better. I believe they also have slightly less edge retention.

When a wood strop with diamond spray brings back an edge how is that different than than high grit stone doing the same? I get that the strop is less abrasive, but I'm still removing some metal, right? Seeking to understand rather than challenging.

 

If I could strop on leather with compound and hone on polishing stone indefinitely I would do such.

However one notices that over time the edge will lose its ability to be brought back to the level of sharpeness it was when it was freshly apexed in the 400-1000grit range and further refined.

One cannot hone and strop the edge indefinitely without needing to set the apex again.

That is why the saying is stones create as in create the apex and strops enhance as in refine the apex.

If the apex is worn down, blunt and smooth to a flat plateau than there is nothing to refine. There is no apex.

 

Are these "polishing tapes" just lapping film?

 

Got it. Strop can't create an apex. My brain wasn't working - this seems obvious now that you wrote it. And I've tested it and know better. Just haven't looked at this for a year or so. I get successive less edge retention every time I strop and edge. I'll post a chart if I can find some of my data. (Yes, this will demonstrate my own stupidity for not recalling that I already know the answer to this.)

Found it. This was an edge test from a CRKT Pilar in S35VN. Sharpened on an EdgePro with diamond matrix stones to 17.5 degrees up to the 1100 stone. The variability you see in the trend is likely the margin of error in my testing and the variability in the rope diameter. I'm guessing my results are +/- 10% or more for any given cut test. Cut test are patterned after what Pete of Cedric & Ada does.

I didn't strop the same number of times for every test, but I averaged about 15 passes per side. I changed sides after 3-4 passes max, and the last 8 passes we're always 1 per side. If I recall I saw no additional benefit after 15 or so. That will vary by steel and hardness, of course.

 

Brent Beach has done some very good work on this factor, basically the edge develops what he calls a "wear bevel" that increases the edge angle along the apex. When you hit it with a conformable abrasive, it follows that geometry - the edge gets sharp along the apex but at a higher angle. After a bit of this the apex is just not acute enough to cut well and the (average) strop isn't aggressive or precise enough to grind the entire apex flat.

Anything you use as a "strop" that is going to overcome this will need to be very firm. I've had good luck keeping carbon and low alloy stainless at mid to low 50s RC very sharp using paper and compound on a washboard, but used like a finishing stone - scrub just behind the apex to where the edge isn't catching on the paper and slowly work into the edge.

Arguably, this is not any faster than using a firm abrasive and touching up on a strop.


http://www3.telus.net/BrentBeach/Sharpen/index.html

 

Did you actually use 6 nano meter diamond for stropping?

 

Nope. 6 micron. Good catch. I work in tech and have nm on the brain. Will correct it.

 

I have a slightly related question. I often see stropping leather mentioned but not honing steel. AFAIK, they both generally achieve the same thing--edge alignment (versus material stripping), while the leather also cleans up the edge. Is the use of a honing steel generally frowned upon here, or is it simply considered unnecessary if you have a stropping leather?

 

David, what material did you use for a strop and what carrier for the diamond?

 

Bass and balsa wood. 1/8" or 1/4" from a hobby shop. I cut it to fit EP blanks as needed. I use commercially available diamond stropping paste and diamond spray from a local knife shop in Portland but I suspect they do. The spray has their label - not sure if they make it themselves. It's the place BBB has mentioned and is a nice knife and accessories shop.

Additional info you didn't ask for: The paste seems to last a little longer on the wood than the spray, but I haven't tested it. I prefer the spray because it dries faster than the paste. One bottle of spray seems to be lasting me a very long time. The both work well.

After experimenting with cleaning the strops I found it easier and faster to just sand them on 220 grit sandpaper to get to fresh wood, then reapply compound.

I'm sure you know this, but the edge off your 1100 stone has rope jumping off the blade. I went to 17.5 degrees because I didn't want to be cutting rope all day.

 

I wonder what your results would have been if you had stropped with 25 micron diamond? It would work a lot closer to the 17 micron in the 1100. I still want to play with "sharpening" with firm leather, I know that it can create with the right process parameters.

I know for leather using water as a carrier leaves it a lot slicker than any of the paste carriers I have tried, which in turn convexes the edge less. I only strop guided at the same angle as the stones by the way.

 

Same for me on the angle - no change for my strop. I'll see if I can find larger micron spray. A quick search says I can't. I saw some very expensive 15 micron spray. I'll keep looking. Since the 1100 stone is 17 micron would I not want to go smaller, such as 10 or 15 microns on the strop rather than larger? Perhaps I'm not understanding your intent.

 

My thought is on the rope cutting experiment only. The softer "bond" means the abrasive will not work quite as aggressively as it would in a firmer "bond". If you want to maintain the same edge as the 1100 Matrix stone then you need to use a larger abrasive on the strop, the softer the strop the larger it needs to be. You would also need to lower your angle a little to compensate for the convexed bevel of the softer "stone". I am not advocating it would be better, just that it may work.

 

Got it and thanks much. Will give that a try.