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strop spray vs. abrasive film

Fri Jan 18, 2013 2:45 am

Ive been reading a lot about higher grit sharpening and stropping and it boils down to strops with a micro diamond or CBN spray, and micro abrasive films by 3M most commonly. Does anyone have any insight on comparing these products? The sprays go down finer to .1 micron opposed to .5 from what I see in films, but I personally dont think that difference will be noticeable on my behalf.

Jared

Re: strop spray vs. abrasive film

Fri Jan 18, 2013 8:22 pm

Sprays can go down as fine as 0.025 microns - ten times finer than quarter micron, so your finest finishes are with polycrystalline diamond at that level of finish - 0.025, 0.050 and 0.1 being the finest. (available in mono directly from me as well). And all of the grits available in film are available - most on Mark's site too. For the finer grit particles, I strongly recommend nanocloth or Kangaroo leather for a base or substrate to apply the compounds as this produces minimum interference with the particles.

There are various diamond film grits available. The finest film in diamonds is 0.1 microns. It is a very delicate film, requiring a good bit of care to use. I'd suggest compound at this level for most. Between 0.5 microns and coarser up to about 9 microns, I have a newer film preparation that is a good bit more robust that holds up very nicely. Long wearing.

I also have both alumina suspensions in 1 micron 0.3 microns and 0.050 microns. This is a more affordable preparation than CBN and diamonds and works quite nicely for a number of choices, particularly on leather and linen substrates. I also have aluminum oxide and chromium oxide available in films too in this finer grit range.

Please send me a PM if you want even more info on these products. Or just ask about it here.

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Ken

Re: strop spray vs. abrasive film

Tue Jan 29, 2013 11:31 pm

Thanks for all the info. quite a bit more than i was expecting. since my initial post i bought a variety pack of abrasive films in 9,5,3,1, and .3 micron. they are an excellent compliment to finish after my 1k and 4k shapton gs. Leaves as close to a mirror polish as i have seen on my bevel and seems easier to remove the bur on my vg-10 gyuto which is rather difficult sometimes. if anything id like to fill in the gap between the 1 and .3 micron and get something finer, .05 micron maybe? i like the films but also would like to get started building a strop set. your tips and advice are appreciated.
thanks
Jared

Re: strop spray vs. abrasive film

Wed Jan 30, 2013 11:40 am

Reminds me... Ken I need a new bottle of 0.3µ alox :D

Re: strop spray vs. abrasive film

Fri Feb 01, 2013 3:19 am

"Reminds me... Ken I need a new bottle of 0.3µ alox."

I have it - Just let me know with a Skype call / text.

Jared, the finest thing available is 0.025 micron diamond on nanocloth, followed by 0.025 micron poly on Kangaroo leather. I do have a few other options too.

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Ken

Re: strop spray vs. abrasive film

Fri Feb 01, 2013 5:24 am

Ken, I got a 2x6" kangaroo strop from you and it does a great job naked (no compound, spray, etc.). I use it after the .5 micron CBN. I have Mark's 25 micron diamond spray also and love it as well. When I'm trying for the ultimate edge that I'm capable of I use all three. It seems at this micron level I like more grits and less time with each instead of more strokes with the kangaroo after skipping the .25. I believe it was you who put it like this, the edge needs to be sharp enough for the next level in progression to be effective. An example everyone can understand is there is no need to use a 8000 grit stone on a DULL knife. You would have to spend weeks using the 8k grit on an edge that is still dull. So, how much progress will you get using .1 micron after using 1 micron. Maybe that would work but it seems to me you'd want a grit step or two between 1 and .1 microns. Personally I have gotten no benefit from .1 micron CBN. After .5 CBN or.25 diamond sprays the .1 on nano-cloth seems to make no difference. So, either my skill is not good enough to get performance out of .1 or I just can't tell the difference. Six years ago I didn't use an extra-fine stone (Arkansas I think) because the edge got duller than it was after a med. or fine grit. Now that my skill has improved I'm sure my lack of success was because of a lack of skill. I used to think finer grit stones were just a waste of time. Who doesn't like to blame the equipment? :) I forgot to say I don't know what micron naked kangaroo is but it seems to be less than .5. If the grit of the strop material is coarser than the compound that would seem like a waste of coumpound.

I want to thank the people on this forum for the help I've received. I've learned a lot.

Re: strop spray vs. abrasive film

Fri Feb 01, 2013 8:37 pm

Yes. 'naked' Kangaroo does something and is actually quite nice. Naked Nanocloth does nothing or close to it. So the 'roo has it's own properties. With the nanocloth you ONLY have the effect of the compound. So a pure compound effect of the 0.025 plus the nanocloth gives the finest and purest compound effect. Hence it is the most extreme edge. I have tried 0.015 micron poly, about 1.5 million grit, but couldn't detect an improved result and the cost was prohibitively high (like 2 oz for ~$400) so I never offered it as a product.

So there is an interesting 'blend' of variables. On the one hand, each stroke potentially contributes error. On the other, finer compounds DO produce sharper edges - I'm convinced of this. I just touched up an edge going from the 15k Nubatama (which I suspect but cannot prove is finer than 15k, especially working the mud a little and very light strokes) to a 0.1 micron CBN emulsion on kangaroo. I did this to touch up a Nubatama petty knife giving me a superb edge, far sharper than what I get with .25 micron CBN mono or poly. Would I have gotten an even sharper edge with 0.5 or 0.25 inbetween? Perhaps so.

There is also the interplay between leaving a slight degree of toothiness (yes I detest this term) and smoothness. For a pure effect of smoothness, clearly the intervening grits would increase smoothness, but perhaps at the risk of rounding off or making it less acute. For maximum effect excellent angle control and light pressure minimize these confounding variables in chasing the ultimate edge. Here the thinness of kangaroo leather (and nanocloth) along with it's smoothness and draw are very effective.

The naked 'roo seems to have a bit of a burnishing effect, unlike the nanocloth which seems to be purely abrasive (surface removal). You feel this as a difference in draw characteristics. When we are abrading at this fine a level we are close to having similar forces for burnishing vs abrading, each moving metal around but one from surface deformation and one from surface removal. It is a fascinating interplay to contemplate.

One test I keep coming back to is push cutting paper performance. This test is often done incorrectly. The toughest test is to hold the knife perpendicular to the edge of a piece of paper. Right on the edge, no running start, no lateral forces. Then come straight down with NO slicing motion. Then measure how far away from your pinch grip on the paper you can cut. This test is negatively affected by knife thickness and angle, so that a really thick knife like a western deba should be held at a consistent angle for testing. Sample several places along the edge as this test is localized to the spot tested. Use a well dried knife and paper.

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Ken
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