Welcome! Log In Create A New Profile

Advanced

Sharpmaker : CBN rods : 400 grit/mesh

Posted by CliffStamp 
This forum is currently read only. You can not log in or make any changes. This is a temporary situation.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 23, 2014 02:55PM
Cliff: How long are the CBN rods supposed to maintain their aggression?

---------------------------------------------------------------------------------------------------------------------------------------

Bill22252 on YouTube. "See you space cowboy"

Resident Emerson Fanboi

Folding knives are fun, fixed blades are important.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 23, 2014 03:19PM
Bill, that is a great question, the answer however is not so simple because the rate of wear is dependent on :

-if a fluid is used
-how much force is applied
-what is being cut

I am going to do a comparison shortly with the side I am using and the untouched side to see if I can notice a difference. However please keep in mind :

-I am using a cutting fluid
-only enough force to do the cutting is being applied

I am grinding a mix of low (420, plain carbon low end cutlery) and high carbide steels (Elmax, S30V, etc.) .
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 23, 2014 11:20PM
Nice analysis. I am surprised that the medium stones did not remove fairly soft damage steel and instead essentially steeled them. Did you use the edge or the flats? I had assumed the flats.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 24, 2014 12:04AM
Quote
chad234
Nice analysis. I am surprised that the medium stones did not remove fairly soft damage steel and instead essentially steeled them.

I didn't expect that either which is why I threw as much data at it to confirm I wasn't just seeing some odd spiking. A critical measurement was to :

-check the sharpness after just two passes

this was key as the response was almost immediate but there is no way that the material removal is that fast. Then I did the followup checks with a smooth steel and then cut the edge off and used the mediums again to check and confirm.

Quote

Did you use the edge or the flats? I had assumed the flats.

I used the flats initially but the blade is very awkward to hold/see so I used the corners to start for the first 5 pps and then the rest on the flats, that improve the performance slightly.

I did have one further check I wanted to do but ran out of cardboard which was to do a run with a much more significant grinding say 25-50 pps on the medium rods because this should have increased the edge retention. I may check this at a later date.

Now of course there is nothing preventing you from cutting the edge off and reforming it just on the medium rods completely and skip the Bester but this requires a long time and I would have to clean the stones too often and it only takes just 1-2 passes with too much force and you have to start over.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 24, 2014 01:34PM
As an update, I recently did an experiment to look at the edge retention on a push : [www.cliffstamp.com]

Details :

-used screw ties were used as the blunting media
-cuts done almost on a push (very little draw as it is hard plastic)
-push cut Espirit thread to determine sharpness

I expected that the CBN would be behind here because the finish is much more coarse and while it does well for slicing it would not do that well for push cutting. However the experiment hit a snag because :

-cutting thick plastics causes a very low rate of blunting
-the blunting is not at all consistent

I needed to make a 1000 cuts into the screw ties to even produce a significant loss of sharpness and even then it was only on certain parts of the edge, the vast majority of the edge, the majority of the edge is at almost as boxed in sharpness after the 1000 cuts.

But even more interesting with two runs done with each there is a very significant difference in how they behave :

-the CBN has a lower initial sharpness

There is no surprise here it is push cutting sharpness and that increases with polish, but what was not expected is :

-the edge durability is much higher with the CBN

Now I have only done two runs with each, so this still may be nothing but random but :

-both runs of the as-boxed showed the edge reflecting light in spots which were clearly visible by eye
-under magnification you can see the edge is clearly dented/bent
-this starts to set in at a few hundred cuts and just gets worse

In comparison :

-one run of the CBN showed no light reflecting
-the second one showed two small spots barely visible

Under magnification the difference is quite obvious - which raises the question as to why it is happening? There are three possible causes :

-the more coarse edge of the CBN is doing more of a slice and stabilizing the edge
-the angle is slightly higher on the CBN than the as-boxed edge (a couple of degrees)
-the initial edge is power sharpened

Now it is possible to verify which one of these is the issue, unfortunately I don't have enough material to do it, what I need to do is :

-resharpen with the CBN at the exact same angle, just tilt the Sharpmaker to lower the angle slightly
-constrain the cutting to a pure push cut (rocking cut)

If neither of those made a difference then it points to power sharpening being the issue, this would then be checked by comparing the edge on the fine grit rods which should show an improved finish over both the CBN and as-boxed.

I have some numbers on what I have done and charts and pictures, I'll post them up shortly. However I don't actually have enough material to do any of the above experiments so that will have to wait until I get it (which is just random).

I think what is happening is a combination of all three effects.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 25, 2014 12:56AM
This cutting trial gave me a new appreciation for cardboard because :

-it is far more physically demanding
-the rate of blunting is extremely low
-blunting is extremely erratic
-it puts sharp shards of plastic everywhere

I picked up a few more ties and was considering doing another finish but instead was really curious and did another two trials with the as-boxed blades and am glad I did because the results were significantly different than the first two. The damage was still greater than with the CBN rods but not nearly as strong as the first two runs. That is the problem when trying to draw conclusions from small samples where there is lots of random influence often what you think is something significant is nothing more than noise.

The results :



This is a sample of what the edge looks like on the as-boxed edge after the runs, it is commonly dented/rolls. In contrast :



This is the edge of of the CBN rods after the cutting.

Note that those little hooks are actually what was left over from the kind of damage from the as-boxed edge, they are not caused by the cutting itself. This is a sign obviously that I could have cut off more steel before sharpening and that the performance of the CBN rods was likely lower than optimal.



The initial sharpness is lower with the CBN rods, that was not surprising because this is a push cut and that is optimized for a high grit finish. However the interesting thing is the TCE starts to get closer the more material is cut and it looks like if I continued that the CBN would overtake the as-boxed finish so the cutting lifetime would be higher.

There are a few interesting experiments that are suggested by this, one would be just to do a much longer cutting comparison but the rate of blunting is so slow I think I would need to do at least 10k cuts to map out the full lifetime and that is just a massive amount of plastic to be cut. But I might do it at some point in time out of curiosity. I might also do another couple of CBN runs at a slightly lower angle (a couple of degrees) as that is the part I am most curious about.

--

However the main question I wanted to answer was could the CBN rods be used to sharpen those utility knives if they were used for mainly push cuts on harder substances like plastic and the answer is definitely yes.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 26, 2014 08:56PM
Video overview :



Re: Sharpmaker : CBN rods : 400 grit/mesh
July 26, 2014 10:19PM
Interesting video as usual. What happened to people like Mike Swaim?

On an aside, I recently acquired a set of the CBN rods. I must say that my initial impression is a resounding meh. The rods are nice, with a consistent surface finish. They are nice and coarse and could certainly prove useful as a tool for heavier sharpening. Unfortunately, I really don't know how I am going to utilize them. I am not a fan of the sharpmaker for a number of reasons, mostly the low aggression of the stones, as well as the angle limitations. If you have a bunch of knives that have varying factory bevels, you are going to be doing a lot of grinding, CBN or not. While that really isn't a problem with non-recurved blades, it is going to be a rather miserable experience on thickly ground blade.

I recently decided to try and resharpen my abused and misground Spyderco Street Beat using the 40 degree setting, but a awful lot of work is going to need to be done to get to that, let alone 30 degrees.

---------------------------------------------------------------------------------------------------------------------------------------

Bill22252 on YouTube. "See you space cowboy"

Resident Emerson Fanboi

Folding knives are fun, fixed blades are important.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 26, 2014 11:57PM
Quote
Bugout Bill

If you have a bunch of knives that have varying factory bevels, you are going to be doing a lot of grinding, CBN or not. While that really isn't a problem with non-recurved blades, it is going to be a rather miserable experience on thickly ground blade.

I think I need to do some videos showing some regrinds in real time because I do that all the time and it isn't a significant amount of time. I even flatten primary grinds all the time. It takes a little time, how much depends on the steel/size, but in no cases does it take longer than watching an episode of Drunk History, unless you are just tooling around on a very mismatched stone/steel combination (which I do all the time).
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 27, 2014 12:16AM
Cliff, those would be very helpful to see.

On the street beat, I was trying to thin out the ridiculous bevel using the corners of the rods. It would certainly be doable, but I would be sitting there with the sharpmaker for a lot longer than if I was just using something like a DMT Extra Coarse.

---------------------------------------------------------------------------------------------------------------------------------------

Bill22252 on YouTube. "See you space cowboy"

Resident Emerson Fanboi

Folding knives are fun, fixed blades are important.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 27, 2014 12:23AM
How long are you talking about, just roughly?
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 27, 2014 12:23AM
Good, simple idea on marking the CBN rods them using the sides sequentially. I copied.

I tend to use the Sharpmaker for setting micro bevels, not full sharpening. I usualy thin out the apex with a DMT stone or other benchstone , then set the microbevel. The CBN, followed by the medium sets the microbevel fast. Refine on the fine if desired.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 27, 2014 01:00AM
Cliff: To thin out the bevels, probably an hour or two with the sharpmaker. An hour or two with a stone wouldn't be so bad, but (at least in my experience) the sharpmaker requires a bit more concentration than freehand. It could get tiring quickly.

---------------------------------------------------------------------------------------------------------------------------------------

Bill22252 on YouTube. "See you space cowboy"

Resident Emerson Fanboi

Folding knives are fun, fixed blades are important.
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 27, 2014 01:10AM
By thin out the bevels do you mean taking something above 20 dps to 15 dps?
Re: Sharpmaker : CBN rods : 400 grit/mesh
July 27, 2014 01:15AM
Cliff: Yup. I'm guessing 25 DPS to 15 DPS. Even with the factory edge, it still wasn't hitting the sharpmaker at the 40 degree setting.

---------------------------------------------------------------------------------------------------------------------------------------

Bill22252 on YouTube. "See you space cowboy"

Resident Emerson Fanboi

Folding knives are fun, fixed blades are important.
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 01, 2014 12:28AM
Update on the final of the Stanley trilogy :

[www.youtube.com]
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 01, 2014 01:40AM
So much kindling. So few fires...

How much of an effect do you think the stock thinkness had on the usable edge retention? I've been playing around with a utility knife at work and steeling it on my leatherman knife spine to touch up the edge when it rolls. I have noticed the edge will chip out quicker when i do this though the most common blunting so far is abrasive with the edge rounding off. Either way, even dull, i find how thin these blade are make them usably sharp even after doing a cut into my soft arkansas stone. Did this with the first blade so i would have a bench mark of when it was "too" dull and what to look for in use.

what i cut at work. cardboard (anywhere from paperstock up to 3/4" thick and covered in everything that can be found in a rock quarry/mulch yard), paper and plastic bags with thinset, grout and concrete, carpeting, vinyl flooring, carpet runners (laying on concrete floor or a piece of vinyl if i'm lucky), zip ties, that dreadful heavy duty banding for lumber bunks, and finally rolls of coins cause some one thought it was a brilliant idea to wrap them in heat shrunk plastic sleeves.
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 01, 2014 10:36PM
Quote
fervens

How much of an effect do you think the stock thinkness had on the usable edge retention?

The knife will be able to cut at an acceptable level with a lower sharpness the higher performance the grind. And as well the rate of blunting will be decreased as the grind efficiency is improved due to lowering of loads and instability.

Quote

Either way, even dull, i find how thin these blade are make them usably sharp even after doing a cut into my soft arkansas stone. Did this with the first blade so i would have a bench mark of when it was "too" dull and what to look for in use.

Yeah in fact it is rare that I find people replace these in use because they are dull, especially when cutting things like drywall. They typically just replace them when they break them.

Quote

... finally rolls of coins cause some one thought it was a brilliant idea to wrap them in heat shrunk plastic sleeves.

Ha, I should do that the next time I go to the bank.
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 01, 2014 10:42PM
I can see you walking into a bank with a hundred dollar bill and asking for rolls of pennies. Wait, nickels? canada doesn't use pennies anymore right? Or one dollar bills for that matter. Although, i love the two dollar coin trend.
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 04, 2014 10:02PM
As an update :



-cut dirty polypropylene rope on a 2" draw with the ZDP-189 Delica
-primary grind is sabre/flat full zero
-edge had a slight increase in the curvature in the last 0.040" thick to 9-10 dps

The comparison was :

-CBN rods vs Medium rods at 15 DPS

In short :

-the CBN rods had half the initial sharpness but were twice as sharp after 62 cuts into the dirty rope
-both rods were able to resharpen and retain performance

Note this is in contrast to the cardboard cutting where the medium rods had to have the edge reset with the Bester 700 before they could get strong performance. But note the difference with cardboard :

-a softer and weaker steel which is more likely to bend under stress
-a much higher volume of cutting into stiff material
-a very low abrasive material cut

vs this run on the polypropylene :

-a harder and stronger steel
-a lot volume of fairly soft material (opens up in being cut)
-an extremely abrasive material being cut

For those who like some numbers (all numbers are % of optimal) :

CBN :

-Initial : 30 (2)
-Final : 8.5 (7)

Medium :

-Initial : 63 (7)
-Final : 4.3 (4)
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 05, 2014 01:21PM
Updated by combining all the runs to get two average performances to more clearly show the difference between the CBN and Medium rods :

Re: Sharpmaker : CBN rods : 400 grit/mesh
August 05, 2014 04:29PM
Do you see any functional advantage to the CBM over the diamond rods?
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 05, 2014 04:32PM
Quote
chad234
Do you see any functional advantage to the CBM over the diamond rods?

They have a cooler name.

I don't think it would be easy for me to tell them apart if they were not labeled. Long term however there might be durability concerns.
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 09, 2014 04:54PM
Here is a similar piece of work but with the medium and fine rods :



Re: Sharpmaker : CBN rods : 400 grit/mesh
August 09, 2014 05:20PM
- Cutting soft yet abrasive material
- Using a very hard steel that tends to chip rather than deform (ie. ZDP-189)
- Use a medium grit stone to remove the damage

Does this sound correct? What if we changed part of the equation...

- Cutting soft yet abrasive material
- Using a low hardness steel that tends to deform rather than chip (ie. L6)
- Use ???

A collection of info like this regarding various steels would be enlighting to say the least. Spyderco, for instance, could literally suggest a specific, ideal, stone for each of their steels.


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 09, 2014 05:22PM
I think you would need a coarse stone Chum, because the blunting would be through deformation and general wear, so in order to not just push the steel back into place, or so as not to have to do an inordinate amount of passes (that could stress the edge) in order to reestablish the edge you would want something that ground the edge and ground it quickly.

Hopefully that's good thinking,

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 09, 2014 05:40PM
Quote
C Amber
I think you would need a coarse stone Chum, because the blunting would be through deformation and general wear, so in order to not just push the steel back into place, or so as not to have to do an inordinate amount of passes (that could stress the edge) in order to reestablish the edge you would want something that ground the edge and ground it quickly.

Hopefully that's good thinking,

Then when does a very fine grit stone come into play?


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 09, 2014 07:03PM
Quote
Chum

Does this sound correct? What if we changed part of the equation...

The results would change, this is best case scenario for not destressing the edge. Look at what happened when I tried to use the medium rods only on the Stanley blades on the cardboard, they were much worse than the fine rods on the poly.
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 09, 2014 07:16PM
Chum,

I don't think they have much use for "touching up" in the sense of returning a blade to optimal condition (not to be confused with just improving sharpness)...instead they just steel/align it more and don't remove enough material from a stressed edge.

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Sharpmaker : CBN rods : 400 grit/mesh
August 09, 2014 08:38PM
Thought provoking video, and nice explanation of why this is an optimal situation to examine this relationship. I respectfully disagree with one of the tenants of your analysis. As I understood it, you assert that both the terms honing/ touch-up and the practice are non-sense, and are really just incomplete sharpening that needlessly leaves damaged steel on the edge. I respectfully disagree because:

1. The terminology is useful for describing just that- refining the edge back into alignment without fully resetting the edge bevel.

2. As a practice, it has its place. While some may place an emphasis on minimizing steel loss, as you explain in the video, I don't really care about that a effect bit. Rather, my issue is time and immediate ease. Like most, I like my knife sharp, and when it starts to lose performance, i.e. the edge just starts to drag, a few swipes on a fine ceramic rod gets it back to a good level of performance. Then, at some point where the metal degradation starts to become noticeable and I have time, I can fully reset the edge. This is typical in professional kitchens, butchering, etc.

Consider that the amount of work you did on those runs may represent the use of a casual user with many knives in rotation the equivalent of several months or even over a year of use. Getting by with honing and then eventually fully resetting the edge when indicated means having a sharper knife more of the time.

Yes, I agree that ideally, fully de-stressing and resetting the edge would be better in some circumstances. But switching to analogy, sometimes, a simple squirt of dermabond and placement of bandaid is a better (faster, less expensive, and of good efficacy) treatment than a trip to the Emergency Department, administering a local anesthetic and suturing a small cut.

3. I don't mean to alarm you, but some joker turned the clip on your Delica upside down. While I prefer the Delica sans clip, tip down carry is the most uncomfortable placement for me. I also prefer chocolate ice cream on its own, but prefer vanilla when eaten with pie, cake or the like.



Edited 1 time(s). Last edit at 08/09/2014 08:39PM by chad234.