sharpen experiment edge leading/trailing

[Cliff Stamp]

Recently I set out to compare a few hones for a few purposes, one being to "prove" the superiority of leading vs trailing sharpening.

First the edge was set with a 600 DMT stone, results 7/29 lbs on a slice/push through 3/8" hemp. Lots of aggression, would shave and could push cut newsprint but catch in a few places.

1200 DMT, major improvement on the push, little on the slice, 7/20 lbs. Less aggression, but the huge jump in push cutting performance easily compensated. Could slice toilet paper readily.

15 micron SiC, little change, 8/19 lbs. I don't feel this was optimal, it was difficult to sharpen edge leading, the paper was on hardwood. Did not slice the toilet paper well.

0.3 micron AO, 6.5/15.5 lbs, much better, but the paper was cut with the knife in a bunch of places, very difficult to hone edge leadning.

0.5 micron chromum oxide on newsprint on hardwoods, edge trailing : 4.5/9.5 lbs, best performance I have seen to date. Cut toilet paper again but not as well as after 1200 dmt.

I was also measuring the sharpness on thread and cord, but there were problems due to certain parts of the edge being damaged from the paper plus I kept whacking the edge into nails during the hemp cutting because I forgot I had used the block earlier to calibrate impact drops.

What I did learn was that chromum oxide on newsprint gives a much nicer edge than on leather which seems obvious due to lack of rounding I think 1200 DMT + chromium oxide on newsprint should give a possible 50 / 50 sharpness on thread light cord (100 g), which I think is optimal.

In the above at the end it was 75/121, but that included the damaged edges, it was 65 / 65 in the best regions where the rope cutting was performed. Based on the ability to slice toilet paper after the 1200 DMT stone, it would be really nice to see a similar but finer flat diamond plate.

The newsprint buffing was really light, 20 passes per side on a 1"x3" strip of paper.

-Cliff

 

[thombrogan]

Great test! What sort of blade were you using?

Perhaps you could try edge-leading using both an angle guide (i.e. binder clip or Razor Edge edge guide) and putting the abrasive on top of glass instead of wood? I'd also check the blade under magnification to make sure you're abrading significant amounts of the mylar containing the abrasive.

 

[Nosmo]

Great test. Thanks for taking the time.
I have succeeded in leading edge sharpening on an EdgePro with 3M psa backed, Aluminium Oxide on a Mylar base at 0.3 Microns.
The blade has to be absolutely rigid ( no rock ) and the hone arm bearing was replaced to give almost zero clearance ( no rock ). The base the tape was attached to was ground flat on some rather fancy equipment.

Never done any tests but every time I use the polishing tapes, I use the same hand movement, both leading and trailing with all my tapes up to 0.3 Micron.

 

[Bill DeShivs]

Cliff
Have you tried synthetic ruby stones? The finest grade will polish an edge to mirror brightness and there should be no possibility of rounding the edge.
Bill

 

[cbwx34]

Ok... am I missing something here? Wouldn't a test to compare leading vs. trailing be made by sharpening the same knife on the same medium doing it once trailing, and once leading? I've read thru it a couple of times, and I don't really see the comparison. Or am I just not getting it???

 

[beezaur]

7/29 lbs, etc. -- what does that mean? Sorry, I don't spend much time on this forum.

Scott

 

[Cliff Stamp]

I use the same hand movement, both leading and trailing with all my tapes up to 0.3 Micron.

I assume Ben Dale does the same and the polished edges he has produced give the best combination of push/slicing sharpness I have seen to date. I think it may be a combination of angle control and possibly draw which is an issue, or even the sides of the tape might be lightly raised as I only had them taped tight at the ends.

Have you tried synthetic ruby stones?

No, I have not heard much about them in general. They would be another choice after very fine diamonds and ceramics.

7/29 lbs, etc. -- what does that mean?

29 lbs to push cut with a rocking motion, and 7 lbs to slice on a two inch draw. The push is done on hardwood and the slice is done with no backing, the cord is extended past the edge of a piece of hardwood which has a slot milled in it to accept the rope.

What sort of blade were you using?

South Fork, S30V, 60 HRC.

...on top of glass instead of wood?

That is funny, I have a glass lapping plate which is flat, that should give a more uniform surface. I was inspecting the edges under magnification to make sure the edge was being hit and the scratch patterns were uniform. I don't think the 1200 DMT results were optimal because I was using a small diafold and it was cumbersome after moving from the large benchstone of the fine diamond.

Wouldn't a test to compare leading vs. trailing be made by sharpening the same knife on the same medium doing it once trailing, and once leading?

The title is actually more of a joke, this is why I had prove in quotes. I have argued for some time that edge into should be more optimal for several reasons, however the above work actually shows a more optimal edge with edge trailing on 0.5 micron chromium/aluminum oxide on newsprint than edge into with 0.3 micron aluminum oxide.

The work as a whole was mainly to show the effects of polish/aggression on performance for the review of the South Fork, how the grit finish influences cutting ability, and that the results can be very significant, more so than the steel, and even comparable to the geometry, note the difference in forces are *very* large, and all edges are sharp enough to shave, push cut paper, etc. .

I origionally intended to compare the 0.3 micron aluminum oxide paper edge to the 0.5 micron chromium/aluminum oxide on leather results that I posted awhile ago which were 6.5/12.5 with the same knife, as I think it should have produced a better edge for several reasons, but it didn't turn out that way. However chromium/aluminum oxide on paper did produce a better edge than on leather, though I wasn't expecting it to be as good as it was.

I have to repeat all of it at least once more as a stability check and this time I will tape all paper edges and put them on glass. Comparing them directly would be very informative, I don't think it is possible for some though, can you hone edge into on loaded leather for example?

-Cliff

 

[DGG]

Cliff -

I would like to see some close up edge pictures for the various grits. What type of steel was this? Isn't your 7/29 response backwards? I would have thought the slice cut to be the lower number and the push cut the higher.

 

[Cliff Stamp]

The blade was a South Fork from Phil Wilson, S30V, light utility pattern, 60 HRC, full deep cryo quench. The edge was initially set at 15 degrees, I lowered it to 10-12 as I do most edge comparisons at that angle. The above can be seen in a table at :

http://www.physics.mun.ca/~sstamp/knives/south_fork.html#grit_table

As I noted I don't think as of yet some of these are optimal, I'll repeat this a litte more carefully and stabilize the results and hopefully get more precise thread/cotton measurements.

Some things are interesting though immediately even with the rough first pass, note how well for example the push cutting of thread correlates to the push cutting of 3/8" hemp, this leads to the idea that the wedging forces are only a very small part of the total force with this knife.

As well after buffing on the loaded newsprint, the edge retains solid aggression on a slice while gaining push cutting performance very strongly. In the past I have seen, as many others tend to note, that buffed edges go smooth, and I don't think this is necessary with proper technique.

You have to trade some aggression yes, but it doesn't need to be as extreme as often noted. Spyderco and Dozier for example can produce knives which do very well in both at the same time. The obvious adjunt to this would be if the above knife in each variation was used to cut say 250 pieces of 3/8" hemp on both a slice and a push, how would sharpness be effected.

Yes the 600 grit DMT finish is taking more force on the slice initially, however what is the rate of blunting, does it eventually over take the chromium/aluminum oxide polished edge on a slice and start taking less force? At what point then would this happen? This would then allow different edge finishes to be optimal given how much material is needed to be cut - which is an interesting complexity.

In the past I have seen very strong edge retention on a slice for coarse edges, however in general I think the highly polished edges were less than optimal based on the above and after seeing blades from Dale, Dozier and Spyderco which retained a solid bite even at a high polish.

Based on this I think that now the behavior, when both are optimally sharpened, is more complex. More coarse edges will start off with more force but degrade slower on a slice, on push cuts its trivial, they start off worse and get faster worse, but you never want to use them for push cuts anyway so that isn't very interesting.

As a further complication, is the inherent slicing aggression actually due to some property of S30V? In the past I have not found this to be the case as if often promoted, but again this could be masking due to lack of optimal technique. How does pure 1095 respond in sharpness to the same set of abrasives as it contains no alloy carbides only the very fine cementite.

-Cliff

 

[Dog of War]

Very interesting information as usual, Cliff. Thanks.

Could you elaborate a little on using chromium oxide with newsprint - is this the waxy green CrO stick, powder, paste .... ? If not paste, how are you applying to the paper? I assume the hardwood is just for a flat, even backing surface and you rest the paper on it during stropping, not glued down or anything.

 

[HoB]

Very nice test, Cliff. Can you describe the 0.3 AO some more. Is that the 3M mylar backed abrasive sheets that Lee Valley sells?

What was it, that made the edge leading stroke so difficult on the 0.3 micron AO? Did it bite into the paper?

Have you compared leading edge vs trailing edge on the AO paper?

I,too would wish for a finer diamond stones. They are available but they are very expensive:
http://www.japanwoodworker.com/dept.asp?dept_id=13121
They actually came down in price, they used to be on the order of $600 for the combination stone!

Sorry for the barrage of questions.

 

[LHD]

I must say, I love reading your posts.

Im not expert like you but I'm wondering how this would be different if you were using VG-10, M2 or ZDP-189. Id also like to see your setup for the news print. What do you think about hitting a leather strop a couple times before finishing on impregnated newsprint? Does the leather round the edge to the point that its worthless to follow up with the news print?

 

[db]

Have you found a sweet spot, grit size, for both push cuts and slice cuts? I am guessing that scratch paterns could effect this once the sweet spot is found.

 

[Cliff Stamp]

Have you found a sweet spot, grit size, for both push cuts and slice cuts?

1200 DMT seems to have a nice balance of slicing aggression and push cutting ability, 600 DMT is too coarse to do a lot of things, you can't for example do straight push cuts on flimsy material, so it is a highly focused edge. I think to really fill the above out you would need to correlate it with edge retention work. I think this would be useful both in terms of rope/cardboard as well as just carry and use. As a kitchen knife for example, what is the sharpening frequency/time with each finish. How often can they be repeated before the grit has to be stepped back? I don't think this is an issue at all with DMT's, but can you just keep stropping on the chromium/aluminum oxide and have it retain that decent bite?

Could you elaborate a little on using chromium oxide with newsprint - is this the waxy green CrO stick, powder, paste .... ? If not paste, how are you applying to the paper? I assume the hardwood is just for a flat, even backing surface and you rest the paper on it during stropping, not glued down or anything.

Yes, it is the green bar which I used like a crayon on the paper and smoothed out with the finger, it doesn't have a nice uniform coating, just a bunch of dark streaks. I taped the paper on both ends to hold it in place.

Can you describe the 0.3 AO some more. Is that the 3M mylar backed abrasive sheets that Lee Valley sells?

Gator97 sent me a few pieces two years ago, in usual timely fashion I finally got around to using them last week. The paper is so fine that the only way I knew which side was the abrasive is that the other side it shiny and it is the same on the 15 micron (which feels like fine sandpaper). The 0.3 micron is so fine it doesn't feel like an abrasive, however it does quickly remove metal and darken.

What was it, that made the edge leading stroke so difficult on the 0.3 micron AO? Did it bite into the paper?

Yes, it hits the sides, and you can't tape them as it cuts into the tape, tried that last night. I tried glass, but had problems because it was a huge lapping plate and it was awkward to use on the corner. I only tried the 15 micron and could not improve on the previous result and I found it tended to produced an edge bias easily where it would only shave on one side. I have some metal sharpening slats around somewhere which should do well, or I may just lay them on the DMT benchstone which is covered by a couple of layers of newsprint.

Have you compared leading edge vs trailing edge on the AO paper?

I will. I also have the same chromium/aluminum oxide abrasive in paper form from Lee Valley which would be informative to compare against the block on newsprint. They promote it as having higher cutting speed, but the newsprint was so fast that it took essentially 1200 DMT to optimal in less than two dozen passes per side.

I'm wondering how this would be different if you were using VG-10, M2 or ZDP-189.

So am I, I think it would be interesting to see 52100, D2, ZDP-189, and similar as these are all interesting benchmarks. 52100 is a very fine grained tool steel, D2 is a really coarse grained and heavy carbide aggregate tool steel, and ZDP-189 is well ZDP-189.

What do you think about hitting a leather strop a couple times before finishing on impregnated newsprint?

That is an interesting idea, it might be interesting to see if plain leather or plain newsprint does anything productive.

-Cliff

 

[Dog of War]

Thanks, Cliff. FYI, I've applied CrO 'crayon' to paper before, and a small amount of WD40 lets you spread it out nicely. However I didn't have much luck using it to strop.... didn't work at it very carefully, or for long, though, so need to try again.

 

[LHD]

Any chance we can see some pics of your setup? Id love to try to copy what you've got. I'm also curious how impregnating your abrasive into cardboard thats had the corrugation crushed compares to news print.

 

[Cliff Stamp]

You have to have it very sharp before stropping for it to give optimal results from what I have seen. I have had little success in tuning up a poorly formed or heavily burred edge, but others tend to do well. I am also wondering now if the results I talked about awhile ago about loaded leather dulling edges due to burr cracking would be similar on loaded newsprint.

-Cliff

 

[LHD]

Generally I sharpen my knives as to as polished an edge as I can get with either my edgepro, benchstones or sharpmaker. Then I finish it up with a strop of some sort. I've found that if I take a sheet of cardboard and stack books on it for some time or put it in an industrial press for a few minutes that I get better results stropping with it than I do with leather. The only time this is not the case is when I have a utility edge with a very course grind on it. A field knife or something that needs larger blade serrations than a pocket knife. Then I have better luck with the leather and my running hypothesis is that the leather folds up into the serrations better than the cardboard and therefore polishes the blade better.

 

[vaquero]

Cliff, which DMT stones are you using? Alan

 

[ghost squire]

Based on the Verhoeven experiments I believe 6,000-8,000 grit is about right before using Cro loaded leather.

PS the particles in cigarette smoke are about 0.2 microns... I'm buying some 0.1 micron diamond PSA papers and 8,000 grit and 1,200 grit stones, in about a month I will post on here and share my results. It won't be anything scientific though...