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High-Performance Blades Sharing ideas for getting the most out of our steel.

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  #1  
Old 10-08-2003, 06:30 PM
jgdarna jgdarna is offline
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getting a good edge....

I know you guys have probably beat this dead horse into the ground, but I spent about a half hour searching with no good results.

Let's talk edges. So I've recently have been struggling with getting a good edge on my latest creation.

My lastest and greatest is a camper/hacker/tactical blade made from s30v. The blade is .185 thick with a bevel that is 1". Thickness at the edge is .020. Oh yes...HT is by BOS so it's good.

I've been a fan of the microtooth. It always seemed like when I used the polished edge the balde would always state when I went to turn a 2 x 4 into toothpicks.

So I've probably sharpened this beast about 15 times already just trying to get a good performing edge. Like I said the knife will be used mainly for camping. So I'll need to have an edge that will slice wood(of any type) Chopping wood, cut rope, skin out any critters that I might take during hunting.

Now I know that the "ALL PERFECT All in ONE Knife" doesn't really exist. But So far I haven't been able to get a good edge that I'm happy with.

What are most of you guys using as a final edge for campers.....Polish-Microtooth. And more importantly how are you guys doing your sharpening.

Thanks guys,

Jimbo

P.S. I've tried the "extra" stropping for the s30v and I've actual had negative results.


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  #2  
Old 10-09-2003, 02:22 AM
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tonn tonn is offline
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I never used this steel but... You should try some different stones. If your blade is relatively soft, then harder stones makes better edge. Norton India oilstone makes a good, sharp and very agressive edge.
With harder blades a soft japanese waterstones may be a good.
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  #3  
Old 10-09-2003, 06:35 AM
Jason Cutter Jason Cutter is offline
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Hard steels

I find that in the field, it is hard to go past diamond sharpeners. I have a number of the fine grade (Red) EzeLap small stick-type sharpeners that do quick work of the high tech steels. They are quick on knives with thicker bevels and are really the only way you can effectively sharpen the new CPM type steels without taking a day and a night.

The coarser grade diamond stones are even faster and gives that toothy edge which slashes well through meat but be careful if trying to push cut - it'll bite deep through skin !! Don't ask me how I know !!

Strap one of those (you chose what grade) to each sheath and you'll be assured of long happy use of your knife in the field. Coarse is about ?120grit, Medium is about 240grit, Fine is about 600grit and ultra fine is 1200grit.

Be aware that even though they are good NONE of the diamond coated hones last forever. Jason.


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  #4  
Old 10-09-2003, 09:33 AM
Jerry Hossom Jerry Hossom is offline
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I think the problem with sharpening S30V is all that free chrome which is gummy stuff. I'm a strong believer in the polished edge, which if properly formed will certainly bite into pine without much trouble.

I use convex edges, shaped on a slack belt, though in the past year I've been using a rotary platen so I can better control the shape of the convex. For fine slicers I keep the convex shape flatter, and for choppers I allow it to be more rounded.

I think one of the problems some folks have with polished edges is that they polish them too much at the very edge, making the final angle there a whole lot steeper than you think it is. It will shave, but not hold up long and will tend to skate with glancing cuts.

When I shape an edge, I lay in the bevel angle I want with 120 grit (80 grit on BIG blades), and follow that by carefully raising a wire edge at the same angle with 220 grit. From that point until I am on my next to finest belt I try not to touch the edge again. I then use the 220 to break the corner on the initial bevel to begin shaping the convex. Fron there on I use each successive belt to sand towards the edge (without touching it but maybe only slightly) and up the blade to extend the convex. I go through Norax 45, 30 and 16. Sometimes with small knives I finish with a Norax 5. With the next to last last belt I use I spend a lot of time very carefully raising a wire. The important thing is to not let the belt lap over the edge, but just to sand it smooth. the final belt is for polishing the whole convex, again being careful to avoid allowing the belt to lap over the edge.

With that final wire formed, I touch the blade to a loose buff with white compound and clean off the wire, which at that point is pretty fragile and comes off fairly easily. If any tends to cling, I strop it off. It's important to avoid letting the buff run over the edge, so I keep the edge pointed well away from the buff.

The problem with a slack belt is that it wants to run up over the edge if you push into it too much. Since you tend to do that instinctively with finer belts, you often round the edge into a steeper angle without realizing it. Avoiding that takes some discipline. I suspect that's the source of your skating problem.


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  #5  
Old 10-10-2003, 07:07 AM
jgdarna jgdarna is offline
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Thanks for the thoughts guys,

I usually start out using a fine silicon carbide stone. Once I have a nice fresh edge I move to a hard ark stone. I've found that jsut a few strokes on each side works the best. (I also use a marker to match the orginal angle) After that I goto the strop for a couple strokes on each side.

I've pretty much confirmed that the more I strop....the duller the balde. But that's probably something I'm doing.

So I'd say that I have a microtooth/polished edge.

Good thoughts on the edge geometry Jerry, I try to keep the same angle.....If fact I'm ultra anal about it. I learned a long time ago that the best edge is a nice straight edge.

I did finally get an edge that I'm happy with shave a 2 x 2 down to a toothpick and still shaves hair.

Jerry why do you perfer the polished edge?

Thanks again guys


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  #6  
Old 10-10-2003, 10:36 AM
Jerry Hossom Jerry Hossom is offline
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It's about all those little microteeth you're talking about. If you think about the structure of that edge, what you have are a series of little pyramids sitting along the edge, and the only thing that's sharp is the top of the pyramids. The areas in between are necessarily dull, because they end before they get to the real edge. Unlike a polished edge, those little teeth are exposed to stresses from all directions, even slicing, so they are much more prone to breaking than a smooth polished edge. Once the tops of the pyramids are broken off you have an instantly dull blade. A smooth polished edge will take a lot more beating before you've micro-chipped or rolled it into dullness.

S30V simply should not go dull with stropping, unless of course it's knocking off the tips of those pyramids.

BTW, you can't even approach ANAL on edge angles compared to the people who are fanatical about woodworking tools. I've been corresponding with folks in that world lately, primarily on the use of CPM-3V for woodworking tools and it's been a revelation. They hold edge angles to the fraction of a degree and polish the edges to the sub/micron level - by that I mean they go down to submicron abrasives. We've looked at some of the more challenging applications there, like mortising chisels, plane blades, and lathe tools (chisels and gouges), etc. They've analysed the results by empirical testing as well as photomicrographs. Very enlightening stuff.

One thing we're concluding, which a lot of people in the knife world have argued for some time, is that edge angle should mean only the FINAL edge angle, and not necessarily at the front of a flat bevel of the same angle. The convex edge, which they in fact found on old woodworking tools used by the old masters and which they thought were simply artifacts of age and maybe subsequent abuse, were in fact the edges those old masters likely applied with their stones as a consequence of doing everything by hand. They just happened to result in convex edges, but they also "happened" to cut better than anything made in the modern era of "better" steels using modern sharpening equipment, applying very precise flat bevels.

Granted, woodshaping tools cut differently than knives, but the strength and integrity of the edges are similar problems. From what I've seen in photomicrographs of M2 tool steel edges compared with CPM-3V edges, I'd say their stresses are much higher than ours. M2 is a pretty tough steel, and I've seen it destroyed.


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  #7  
Old 10-10-2003, 11:20 AM
jgdarna jgdarna is offline
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Cool Stuff Jerry.

Now if I would have to assign a cause to the dulling of s30v, I would say operator error. I noticed that I had a slightly larger angle then the stoned edge, SO I probably was rounding the edge.

But now back to the microtooth. I see your point about the pyramids, BUT if you stone a fresh new edge(down to the point were you get the wire edge) I would think the edge would be more like a serrated edge. Sharp all around but with high spots(pyramids)

Just thinking out loud is all. Like you said, those woodworkers are using their tools in a very abusive condition, If they are seeing better results with a polished edge, you have to take that into consideration.


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Old 10-10-2003, 11:54 AM
Jerry Hossom Jerry Hossom is offline
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A wire edge doesn't mean a uniform edge. You can get a wire edge with a 60 grit belt, and that's a pretty ragged edge. As you go down from there in grit size you are sharpening less and less of the hollows between those pyramids. At the finest grits, you're not even touching them, so they are definitely not sharp. What you're creating is more like a saw blade than a serrated edge, close but not the same. That's my take anyway.


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  #9  
Old 10-10-2003, 01:14 PM
jgdarna jgdarna is offline
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oh don't get me wrong about uniform edge. I just learned this long ago that if you have a worn down edge, the best way to know that you have a nice fresh edge is once the wire edge starts to form.

Now dealing with the wire edge is a whole different ball game.

Anyway Jerry how far down do you go with the polish.

I've seen some edges that are mirror finished. I guess that's my vision of a polished edge. Every time I've use one like that I get that skating effect I was talking about.


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Old 10-10-2003, 01:43 PM
Jerry Hossom Jerry Hossom is offline
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I always go to 1200 grit, sometimes 2000.

The only way the edge can skate is if the final edge angle is greater than the attack angle of the cut. Otherwise the edge should bite into the material. That is especially true with convex edges, since they are relieved, i.e. angled back, more than a fixed bevel. As I said, one of the common consequences of polishing edges is to make the final angle greater than you think it is.

There is also another consideration, though knifemakers are not supposed to mention this. Sometimes, albeit rarely, the user is cutting at the wrong angle...

If you want to make toothpicks you may need a toothpick-making knife. Most choppers are designed for fairly high attack angles, and to use them for shaving off thin slices is just not what most are designed to do. You can make one do that, but you'll have to drop the edge angle to below where it will be as strong as you might like it to be for heavy chopping.


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Old 10-12-2003, 08:49 AM
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Gary Mulkey Gary Mulkey is offline
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Jerry,

You must have a better touch than I since I can't buff an edge with a loose cotton buff without losing the edge. I always use the hardest cotton wheel that I can get.

Gary
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Old 10-12-2003, 09:33 AM
Jerry Hossom Jerry Hossom is offline
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Gary, I'm sure that just means there's something different in our setups or something we're each doing that's different. As you know you do a lot of things you take for granted, so you don't even see yourself doing them.

I'm using a 1750rpm, 8" loose buff that's old and worn with a bit of somebody's white compound and I haven't a clue whose or what it is. I've had/used that same buff and bar of compound for years.

I do sometimes find the edge going away when I buff, but I've generally concluded that only happens to me when I get the edge a tad too steep.

Experiences may vary...


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Old 10-15-2003, 06:24 PM
lhytrek lhytrek is offline
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I have tried dozens of different buffing compounds and found the green from K&G to be the best by far. I can't think of the name of it but it was the more expensive green compound. I use this on a sewn buff using very light pressure. For some reason this compound does better than anything else I have tried. But only when I get the angle correct. I have been going down to 400 or 600 grit and getting a really scarry edge but I think I will try going finer and seeing if the edge will last longer. Thanks for all the info.
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  #14  
Old 10-15-2003, 07:51 PM
Jason Cutter Jason Cutter is offline
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Tried Jerry's method.

I just attempted the sharpening on a buffer method that Jerry Hossum described above. MAN !! - it works !!!

I had an O-1 blade, convexed edge with a rough 180grit edge (dull belt) and wanted to polish the lower 1/4inch to make it slick for chopping tests. I polished it edge down with the green chrome oxide on a stitched buff for just a few seconds.

I thought I wasn't hitting the edge - but when I checked the sharpness after - WHOA !!! It knocked off hairs like you couldn't believe. Those hairs were running for their lives.

Jason.


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  #15  
Old 10-16-2003, 10:04 AM
Jerry Hossom Jerry Hossom is offline
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Jason, just so there's no confusion, that's not MY method. It's the method I use but so too do many other knifemakers and have for a long time.

Your using green chrome makes what you're doing somewhat different than what I do. Green chrome cuts steel pretty efficiently and when used on a sewn buff it is even more aggressive, so you're probably doing some actual sharpening on the buff. What I do there is to simply brush off the wire edge and strop it a little. Those are probably milder versions of what you're describing.

Glad it worked though.


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