When stropping what angle should be used?
If I sharpen a knife at 20 degrees should I strop at the same angle or should I strop at a lessor angle, say 19 degrees? The only strops I currently have are leather.
Or is this practice only used when you are trying to convex the bevel. Say you sharpen at 17 degrees, micro bevel at 20 degrees then should you strop at 19 degrees?
This knife sharpening sure can get involve 
but I am having a blast! :woohoo:
All of that is valid. The real key is to strop lightly. Itās ok to strop at the same angle lightly. By increasing to 19 your attempting to effect the angle only and not touch the edge. For touch ups itās ok to strop at the same angle.as the final bevel.only by trial and error to you figure out whatās right for you. If this is your personal knife and it becomes maintenance itās one thing. If your doing some elseās knife to hand off you might be using a different technique based on what you negotiate with the other person.
I think the short answer is, find what works for you. Iāve come to the conclusion that good stropping results depends on a lot of factors that āintertwineā, so what works for one person, may not work for another. For example, one person can strop at the same angle with light pressure, another might lower the angle and increase the pressure. I actually get good results with light stropping at a higher angle, (which is why I was bummed that Clayās microscope pic doing this showed a lot of roundingā¦ my results seem to differ). :blink: Add to that the variety in leather, compounds, etc., and itās easier to just experiment with a few variables, like the ones you mentioned, and ādial inā what works for you.
Iāll add, in addition to angle, pressure, etc., another factor to work with is the amount you do. Try a few strokes, like 1/2 dozen, vs. doing a bunch (which is what a lot of sharpeners do to polish the bevel). Another factor to play with. B)
After writing all the aboveā¦ Wayne had it in his answer. :silly: :lol:
I keep bouncing back and forth between -1 degree and keeping the same angle. Both work very well, but for some reason with my technique (which is very light pressure, after some practice) I seem to get a much sharper āfeelā when keeping the same angle. Iām not sure why that is, because both cut equally well in my basic tests and normal use.
So I guess I can just add +1 to the trial and error advice!
The strops work mostly by drawing or smearing the metal across the surface of the bevel, burnishing it. If youāre stropping on the same angle, itās conceivable that youāre drawing the metal right to the edge and actually pulling it out to a finer apex. This is a topic Iām really curious about but will probably need access to a SEM to study it. Even at 2000x I canāt get a good clear measurement of the edge thickness.
[quote quote=āApexGSā post=5686]I keep bouncing back and forth between -1 degree and keeping the same angle. Both work very well, but for some reason with my technique (which is very light pressure, after some practice) I seem to get a much sharper āfeelā when keeping the same angle. Iām not sure why that is, because both cut equally well in my basic tests and normal use.
So I guess I can just add +1 to the trial and error advice![/quote]
Here are a nice pair of images at 2000x:
The image above is of the edge after being sharpened with relatively new 200# diamond plates.
The image above is of the edge after I completed 40 strokes with the 14 micron diamond and leather strops immediately after the 200# diamond plates. Itās easy to see how the metal was both abraded by the stropping paste and moved around by the āstictionā of the leather, pushing the peaks of the ridges into the valleys and rounding them out.
Great pictures Clay, in your copious free time I would like to see the same experiment done with the 400 grit stones.
Great scope
Thanks for all the input! I keep reading about stiction. Could someone give me a working definition? Conceptually I understand the Wiki definition. When stropping a knife what level, quantity or quality (not sure how do ask) of stiction works best?
This next little study was fun to do though also time consuming since prepping the samples takes a long time for the 2000x images. There is a long process of cleaning the samples and lens, then applying clean immersion oil for each iteration. In order for the 2000x lens to gather enough light and present a clean image, it needs a continuous bond of the oil between the end of the lens and the sample. Every time I take the sample out, I have to add more oil and re-form the bond. Still, all the work aside, itās a blast 
So without further ado, here are some images of an edge that started as nearly perfectly smooth and to which I applied a micro-bevel 30um wide with the 400# diamond plates:
The above image shows the smooth shoulder at the start of the micro-bevel where the diamonds started digging in and cutting little troughs out to the edge.
The above image is showing the middle of the bevel.
Next I lowered the angle three degrees and completed 40 strokes with the 14um diamond and leather strops. I was surprised by some parts of the results. The first image shows the transition at the shoulder between the formerly smooth section and the micro-bevel:
The 14um strops clearly created their own very distinct scratch pattern and wiped out the smooth section. The also had an impressive affect on the scratches from the 400# diamond plates:
Itās exciting to see the combination of burnishing and abrading going on with the strops.
As a footnote, these are the same 14/10 strops Iāve had for a long time and the paste hasnāt been refreshed in months. I did apply some rubbing alcohol to increase the āstictionā.
In the first image of the post above we see the clear junction of the 400# micro-bevel where it cuts into a very polished primary bevel. In the third image Iāve lowered the angle by three degrees and completed 40 strokes with the 14um diamond and leather strops. The effect is dramatic and illustrates why itās so easy to create a convex edge with a couple of facets and the strops. The strops easily smooth over any peaks. In the next little study Iāll try to image the vertex of a pair of facets and then smooth it over with the strops.
Here is a nice view of two facets I created using the 1600# ceramic stones at 20ĆĀ° and at 25ĆĀ° so there is a 5ĆĀ° difference between the two facets:
I admit that Iām shocked by the image below. I changed the angle to 22ĆĀ° and completed 40 strokes with the 14um strops. There is almost no evidence of the junction between the facets - itās been almost entirely erased by the strops:
The only way I can even find where on the bevel to image is by the direction of the scratches. Iām now extremely thankful I used alternate directions with the 1600# stones when making the facets.
Itās amazing to see how āplasticā metal can be. This is an incredible learning tool
Agreed! It really moves around quite easily. I think weāre all going to learn a lot from each other on this forum
I wanted to highlight thisā¦ I find this almost as interesting as the pictures themselvesā¦ had no idea it was this involved. :woohoo: Thatās dedication!
Agreed! It really moves around quite easily.[/quote]
Sliding Metals Show Fluid-Like BehaviorThe first time I saw this sort of thing was a still shot from a high speed video on a gun blog, which showed some metal bar stock being cut by a lathe and how it ābunched upā in front of the cutter as it turned. Hereās the link to the article about it:
Metallurgy is some fascinating stuff! And keep up the good work Clay, from what weāve seen so far it looks like that microscope is worth the work and the wait!
Oh yeah, this is a great video! I saw it a while back and it sort of transformed the way I look at metal. Thanks for the feedback. Itās really fun to do these studies and share them with you guys.
Here is a shot of the same blade after Iāve restored it to basically super polished:
There are a few little marks that I havenāt bothered to remove; enough of the surface is smooth that we can easily isolate whichever grit weāre trying to study. The process to restore the edge was as follows:
Set the angle to 20 degrees> Sharpen with the 1200# ceramic stones until I almost reached the edge (verified by 60x handheld, lighted loupe), flattening out the bevel again> Sharpen with the 1600# ceramic stones until I do reach the edge> Strop with cow and diamond at 14um> 10um> 5um> 3.5um> 1.0um> 0.5um> I then used kangaroo leather and diamond at 1.0um> 0.5um> 0.25um and then 0.125um CBN on nano-cloth and then back to 0.25um diamond on kangaroo.
Do I dare ask how long did it take you to bring this all off restoring this incredible bevel?
Iām guessing about 1/2 hour give or take. I was doing about 50 strokes per side with each grit but my cycle rate is very fast, usually 100+ per minute. Cleaning between grits and switching grits takes the longest.
