Strop + diamond paste question

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thombrogan

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Nov 16, 2002
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Has anyone here used diamond paste to strop-sharpen knives? If so, was there a noticeable difference between diamonds and CrO at similar particle sizes?

Thanks in advance!
 
I have used DMT diamond paste, but not at that fine a level. Such comparisons have been made by others and the Diamond found to be directly superior.

Specifically, in the August 2002 issue of Fine Woodworking there is an article on sharpening abrasives (p36-41) by Aime Fraser. Included are Arkansas stones, DMT diamond plates, wet/dry sandpaper, waterstones (natural and synthetic japanese, and Norton), diamond paste (9,6,3 and 0.5 micron), the Tormek, and CrO buffing compound.

Two plane blades were sharpened with each abrasive using an angle jig to give consistent results. The sharpness was evaluated using high magnification to examine the edge (700x), and then both planes were used on wood in various ways using the ease of cut and finish to rank the finish.

The CrO buffing compound is rated as giving a much lower finish *HOWEVER* it was prehoned with a 1200 grit DMT hone while the diamond paste was stepped down in grits. To see the true ability of CrO you need to prefinish with a very fine hone, such as Lee did in "The Complete Guide to Sharpening" which then shows a perfect edge even under extreme magnification.

The only area where I would see a benefit to diamond paste would be on really high alloy tool steels where the paste may give a more aggressive carbide structure than CrO. I however would not bet on this as being overly significant, and it would take a lot of skill for this to be the limiting factor.

-Cliff
 
Thanks, Cliff.

Once I leave my Spyderco Sharpmaker and EdgePro Apex, skill is often my limiting factor.

I may be getting some goodies in 3V in the next couple of months and was looking to get them to the highest polish possible. I have .5 micron CrO and .3 micron AO lapping film and thought that similar-sized grit in diamonds might do the same job faster.

I'll probably be taking the edge or edges down to 24 degrees combined with the EdgePro and microbevelling with the Sharpmaker anyways, but wanted to know in case I tried getting fancy.

Thanks again.
 
There should not be an issue with speed, this is generally a case of skipping too many grits, for example jumping from a 1000 waterstone to 0.5 micron CrO (~10000 grit). If you progress evenly then honing will be very rapid. The problem comes when you try to polish out very coarse scratches with fine abrasives.

Note in regards to skill, I should clarify this doesn't mean can you get a knife to shaving sharp or not. I can do this readily but would not consider myself skilled enough to tell apart very fine distinctions in edge performance like CrO and Diamond at the same grit level. To do this your tolerance for sharpness would want to be very high, you would consider shaving sharp to be shaving above the skin and you can achieve this level of sharpness readily.

-Cliff
 
I'm at popping hairs off of the skin, but rarely at 'tree-top' level. I'm guessing that the progression from one to the other would require a little more control at holding a steady angle and doing more to eliminate burr formation if I just stay with an EdgePro.

Would there be other factors to consider?

Thanks, again.
 
I tend to go the other way when sharpening, that is, I begin with the coarsest grit necessary and work 'down.'

(I remove as LITTLE metal as I can.)

For example, when using the Edge-Pro on a knife that I have never seen, the first thing that is needed is to make the bevel uniform. I use the 180 grit, lightly, and once uniform I never use the coarse a grit on that knife again.

Depending on the usage, I work down, 220, then 320, then 660. If the knife requires a mirror edge (like for EDC where paper and cardboard are the primary things to be cut), I then polish with the 4000 series tapes.

If I strop, like for a small nagging flat spot or a small ding, I use only a common white rouge and a few licks.

The only time I would use a 'diamond anything,' would be for shaping. I talked Ben Dale out of a diamond against his better judgement, but I have never needed it.
 
Ichabod,

I think that we're mostly on the same page. Though I switch systems, I generally try to set a shallow bevel with coarse, then medium, fine, and ultra-fine grits on both the EdgePro (which I suck at) and the Sharpmaker (with which I get edges that will shave arm hair, but not without also touching skin in most cases).

The diamonds I'm talking about are around 10,000 - 30,000 grit which makes them smaller than the grit in the 4000 series tape.

Maybe before I try them I'll fire off an email to Ben to see if what I'm doing so horribly wrong. I generally sharpen one side until a burr is formed, do the other side until a burr is formed, and continue with finer abrasives until I'm out of stones. Would that be wrong?

Thanks.
 
thombrogan :

Maybe before I try them I'll fire off an email to Ben to see if what I'm doing so horribly wrong.
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Is the horrible part in reference to the fact that you can't get them to shave above the skin? This is far from trivial, and it *really* difficult with high edge angles. To be specific, the lower the edge angle the greater cutting ability at a specific level of sharpness, or the higher the required level of sharpness to obtain a specific level of cutting ability at high edge angles.

If you really want to showcase a master sharpening job get the edge to shave fine hair above the skin when the edge angle is 20+ degrees per side. I can only do it readily when it is 10 or less and it isn't easy then. It takes a lot of care in the finishing step which I usually do on a forgiving medium (leather) to minimize the angle tolerance. I have never done it yet on a hard stone.

I generally sharpen one side until a burr is formed, do the other side until a burr is formed, and continue with finer abrasives until I'm out of stones. Would that be wrong?
Click to expand...

It is not optimal as it tends to propogate the burr. With many steels it can be of benefit after finishing the forming grit to raise the edge angle and give it 1-2 passes with the next grit to cut off the burr and then return to the origional angle to sharpen the edge. A small magnifier (10x) helps a *lot* here.

Personally I never return to the origional angle and put secondary edge bevels on everything for much greater speed of sharpening and durability with an insignificant reduction in cutting ability.


-Cliff
 
Originally posted by Cliff Stamp
To be specific, the lower the edge angle the greater cutting ability at a specific level of sharpness, or the higher the required level of sharpness to obtain a specific level of cutting ability at high edge angles.
Click to expand...

I generally sharpen to 30 degrees included with the Sharpmaker and apply no steeper microbevel (when I'm lucky, the 30 degrees is the microbevel). I recently took my Benchmade 921's edge down to 24 included with a 30 included microbevel and that was awesome, but I'm taking it down to <20 included and am finding out what high wear resistance really is. :grumpy:

originally posted by Cliff Stamp
It is not optimal as it tends to propogate the burr. With many steels it can be of benefit after finishing the forming grit to raise the edge angle and give it 1-2 passes with the next grit to cut off the burr and then return to the origional angle to sharpen the edge.
Click to expand...

To make sure I understand what you're saying, would I be honing away at 17 degrees with 180gr until I create a burr; flip the knife over, and grind at the burr at 20 degrees with a finer hone until it's gone?

Thanks again!
 
I didn't see any listed on DMT's website. There are several jeweler's supply stores and woodworking tools stores that sell diamond paste, but I don't remember seeing the DMT brand.
 
Thombrogan,

It doesn't sound like you're doing anything wrong, perhaps it's just practice.

I will tell you this. Even with the 180 grit, you should be able to develope a uniform burr, then lightly remove it (or most of it) with the same stone, and finish with a few licks of the tape or a strop.

I've done knives like that where you can see my polish/grind marks, and the knife still shaves hair. Something is amiss.

You are right to call Ben.
 
Ichabod,

I get edges that shave and pop hair when the edge contacts skin, but it doesn't shave the tops of the hairs. so, of course, my edges are too dull.
 
thombrogan :

... honing away at 17 degrees with 180gr until I create a burr; flip the knife over, and grind at the burr at 20 degrees with a finer hone until it's gone?
Click to expand...

This would work, but I would work the other side at 17 first and flip the burr back over to even out the bevel. Removing the burr at 20 degrees takes only 1-2 passes, anymore and you are just making more work for yourself. In fact sharpening is pretty much done at that point. There is a small benefit to polishing the entire edge bevel, but it isn't significant unless you are *really* picky. Then again if you are concerned about sharpness at the tree topping level you may feel the need to take that extra step. You may then feel the need to hit the sharp shoulder of the edge bevel to round it out and give it a smoother profile.

I get edges that shave and pop hair when the edge contacts skin, but it doesn't shave the tops of the hairs. so, of course, my edges are too dull.
Click to expand...

Jeff Clark was always one of the proponents of steels having different levels of sharpness I always thought this was mainly a lack of skill on his part (pretty amusing when I think back on it), because I could get fine shaving edges on any steel, even the really crappy ones (you can do this with mild steel even). However after a lot of experimenting, and especially lowering angles done to <10 degrees per side I started to see the differences Jeff was talking about. Even then though I didn't really get that concerned about it because no one actually gets blades that sharp, even the best production and custom blades just shave, and the vast majority don't do that well (less than half I have seen easily). However after recently seeing the extreme job Spyderco did on the Temperance I have been forced to raise my standards, as I should be able to at least equal a production sharpening job (in this case though this isn't by any means easy, no custom I have seen could come even close).

-Cliff
 
Wow...this whole thread blows my mind about sharpening. I thought I did a "decent" job with my Gatco diamond kit. You guys are waaaay out of my league! Thanks for the information, though. This gives me new motivation to get better.

Robb
 
Originally posted by Cliff Stamp
This would work, but I would work the other side at 17 first and flip the burr back over to even out the bevel. Removing the burr at 20 degrees takes only 1-2 passes, anymore and you are just making more work for yourself.[/B]
Click to expand...

Thanks. I can't wait to see how this works out.

originally posted by Cliff Stamp
However after recently seeing the extreme job Spyderco did on the Temperance I have been forced to raise my standards, as I should be able to at least equal a production sharpening job.
Click to expand...

That'd be a great level to achieve of a habitual basis. Their Salsa is also very impressive.
 
Thombrogan,

I do stress that I use my 180 grit to make the bevel 'uniform.'

By that, let's say that the bevel you desire is 18 degrees, and on your knife that works out to a bevel 1/16th wide. (I am speaking in generalities here.)

I then selectively sharpen areas on both sides of the knife so that the bevel is 1/16th wide from choil to tip, and the left side matches the right side.

That means the 'edge,' the cutting edge, is exactly and perfectly right down the center of the blade stock.

Seems a simple thing, but trust me, even though I start to lovingly polish the edge at this point, an edge perfectly centered is spooky sharp in it's own right.

To demonstrate this, I had a Kershaw Whirlwind (probably 440A or AUS-6) with a perfectly centered edge and a mirror polish. A 50 buck knife.

My friend collects Microtech Tantos, and in an edge comparison, my cheap knife out-cut his Microtech USSOCOM in every test we did that afternoon.

I know that his 154-CM knife would hold an edge longer, but he was so ticked, he bought the knife out of my pocket and still has it.

Take a cheap knife and give it a perfectly centered edge. I guarantee that it will scare you.
 
The Tourist :

... see my polish/grind marks, and the knife still shaves hair.
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You can shave with really coarse finishes, the first I have seen dispel this myth was Joe Talmadge who discussed an x-coarse DMT shaving edge on a Cold Steel SRK (after extensive reprofiling), this was years back. Edge alignment is very critical to sharpness, though having the edge bevel perfectly even from one side to the other in terms of height should not make much of an effect.

In fact on a lot of knives the primary grind is off center and thus if you grind both edges on the same angles the bevel will be a lot wider on one side than the other. I have seen them be as much as three times wider on one side than the other (same edge grind angle), this was on production machetes, but I have seen customs where the difference was a factor of two.

The most coarse edges I have seen, 100 grit AO belt could still shave readily and in fact were pushing on being able to pop hairs above the skin. These edges were however *really* acute, I had a D2 one down to under 10 degrees included and the cutting ability of course gets massive enhanced so sharpening to a specific shaving level becomes much easier.

I stil intend to polish that D2 blade up to CrO and see how extreme it will be, the only reason I have not done it is that it is fully convex from spine to edge and thus the sharpening amounts to a full blade polish and on D2 that is really slow, D2 and other such steels really work best with hollow grinds.

-Cliff
 
Cliff,

To be sure, I had a similar knife, a Benchmade Stryker; the right bevel was three times wider than the left. Both bevels were even tip to choil. The edge was off-center, but straight.

Maybe that's the point, a straight edge. I do know one thing, the more perfect any tool is, the better the service. And if I'm very careful with the Edge-Pro, I have the sharpest knife in the room, regardless of cost.

For example, I paid 350 bucks for a Strider AR. The knife was very sharp out of the box, except for the last 5/8's of an inch near the choil. It was 'sharp' there, but not like the rest of the blade. I didn't worry since I bought the knife for strength.

After three sharpenings, the bevel is uniform, and scary sharp the entire way. I believe in this method.
 
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