So I just bought a new Spyderco Sharpmaker and a Benchmade 940 Osborne...

[Obsessed with Edges]

My main tasks include cutting a LOT of cardboard, tape, plastic zipties, and sometimes cloth of varying materials. I know, having S30V for cutting cardboard is a little odd, but having AUS-8 blades or 8cr13mov showed a lot of dulling, requiring a good re-sharpening every few days. I got the S30V mainly for convenience of not having to sharpen nearly as often. After two full work days of cutting over 100 boxes and an equal amount of tough plastic zipties, my 940 is still as sharp as it was the day it arrived with no touchups, and that is factory edge. Still paperbook paper-slicing sharp. Do you think that having it at just 30° is good enough when it needs to be sharpened, taking my everyday tasks in mind? I'm not chopping trees down with it. xD

I'd just use it at 30° for a while, doing the tasks you described, and see how it holds up. You might find it works well for you. But, if it seems to dull a bit sooner than you'd prefer, then add the 40° micro bevel and try that for a while. As you use the knife over some time, you'll develop a better feel for what the edge really needs, in relation to what you're doing with it.

 

[BluntCut MetalWorks]

I never have been able to get my recurve blade ZT-350 fully sharp once I started messing with it.
I was able to split a hair with it, but it doesn't cut well at all.

Been there but fixed that a year ago. You can split/shave/etc hair with soft steel and wire edge as long the edge is thin & strong enough to cut/whittle hair but instantly lose that edge with harder matterials (newsprint, printer paper, food,..). Bottom line, you need diamond to abrade & lop-off VC, where avg s30v VC grain is between 2-4 microns in size. And for fine/polish edge (3 to 0.1 microns), you need to strop using diamond or cbn. Using wrong/soft abrasives (especially sub 9 microns) will abrade the steel matrix and around+under VC, to end up an edge consists of mostly soft steel and weaken VC grains, instead of exposing more % of strongly embeded carbide with sharp edges.

 

[BluntCut MetalWorks]

I made the rig below as a follow up for post #18 of Apex Bevel Geometry thread
http://www.bladeforums.com/forums/s...metry-cross-sectional?p=11342095#post11342095
The rig is more/less a training-wheel for less experience sharpener.

$10 Components: a 2x2 discarded coffee table leg, a 8" hinge, a wood clamp

15 degrees per side setup - do one time label dps for each notch. pictured: VS + DMT 8EF + magnetic protractor

My tinkered BM 940 - it works so great now that I would not trade it for 2 brand new one.

******* In your case - John.
Rather than buy for a pair of triangle rod. I recommend build similar rig as my VertiSharp using 6" hinge and purchase 4" DMT diasharp continuous C + EF ($13+$13), 4" DMT EEF ($20). Once you get more sharpening experience, you can go freehand and re-use the diamond stones.

Coarse - capable of most modest reprofile and serious repair tasks.
Extra Fine(12microns) - normal sharpening bevel set/reset.
Extra Extra Fine (3microns) - offers more polish edge and great for remove burr/wire.

 

[Maniacal Pete]

Been there but fixed that a year ago. You can split/shave/etc hair with soft steel and wire edge as long the edge is thin & strong enough to cut/whittle hair but instantly lose that edge with harder matterials (newsprint, printer paper, food,..). Bottom line, you need diamond to abrade & lop-off VC, where avg s30v VC grain is between 2-4 microns in size. And for fine/polish edge (3 to 0.1 microns), you need to strop using diamond or cbn. Using wrong/soft abrasives (especially sub 9 microns) will abrade the steel matrix and around+under VC, to end up an edge consists of mostly soft steel and weaken VC grains, instead of exposing more % of strongly embeded carbide with sharp edges.

Some great info in there.
So what do I do for S30v in a recurve configuration.
Do you like those little belt sharpeners?
I believe that the make some diamond belts for them.

 

[Obsessed with Edges]

Hey bluntcut, the 'VertiSharp' is pretty slick. Simple, functional, inexpensive. And the hinge idea is very clever. That's the best kind of 'engineering' one could hope for. Very good. :thumbup:

I'll have to head over to the home center to pick up a hinge (I've already got all the rest ).

Only have one question, what is the zip-tie used for? A wild guess: is it stabilizing the lower end of the hinge, inside the block?

 

[BluntCut MetalWorks]

Hey bluntcut, the 'VertiSharp' is pretty slick. Simple, functional, inexpensive. And the hinge idea is very clever. That's the best kind of 'engineering' one could hope for. Very good. :thumbup:

I'll have to head over to the home center to pick up a hinge (I've already got all the rest ).

Only have one question, what is the zip-tie used for? A wild guess: is it stabilizing the lower end of the hinge, inside the block?

Thanks.

I should have remove the zip-tie, it was there as a stone-stop before I made the angle notch for the stone bottom.

As for wood cut out. Originally, I want to use the table saw to cut symmetrical 1" deep lines into a piece of 1"x2"x14" for 10*,12*,15*,16,17,.., 30* at correct angle tilt for the hinge legs to fit in, then glue-sandwich it between 2 un-scored 1x2x14. Oh darn it, I gave the table saw away during the relocation. Oh well, end up with a simpler rig with only 1 notch for the stone.

 

[BluntCut MetalWorks]

Some great info in there.
So what do I do for S30v in a recurve configuration.
Do you like those little belt sharpeners?
I believe that the make some diamond belts for them.

I wrap a dmt flexi-sharp around a rod/tube/bottle where the object curvature (convex) is 3 to 5 times the knife recurve (concave radius). In a pinch, I use SiC wet&dry sandpaper (120-1500 grits). And for my own use - I made diamond flat+convex+concave surfaces starting at 12microns down to 0.1micron. Yes, sometime I lazy and just use the corner & edge of my stone for those slight recurve (by design or excess-weared).

IMO - power belt & wheel sharpener are great for rough grind below 320 grit since fine control is not critical and less heat generate when abrade by large abrasive. Wheel is is a natural fit recurve than belt - sure, there are belt tricks for recurve. My lack of skills & experiences in this area + I want a high level of control, keep me away from them. I rarely use my paper wheels now.

How polish/refine do you want your zt350 edge? For EDC, I would finish at dmt fine or extra-fine edge. If you want a mirror bevel tree topping edge - hit edc edge with 1k,5k,12k waterstones (rounded stone edge for recurve), deburr/dewire using dmt eef at very sligh higher angle, strop (I don't strop, I leading-edge into diamond surfaces) on 1.0, 0.5, 0.25, 0.1 microns diamond/cbn charged strops, finished on bare leather. AND pray that stropping didn't leave you with micro burr and or wire or rounded the edge (start over) :nightmare:

 

[Maniacal Pete]

How polish/refine do you want your zt350 edge?

I just want it to cut cardboard well.
I have a full set of 8-10" DMT diamond stones, and some rods, and am adept at freehand sharpening.
I reprofiled the blade on a wooden dowel covered in Si paper from 350 -1500.
Then I went to the sharpmaker.
I think I may have messed it up there.
I may give up on this one knife and let the factory fix my mistake, its a bugger.

 

[BluntCut MetalWorks]

I just want it to cut cardboard well.
I have a full set of 8-10" DMT diamond stones, and some rods, and am adept at freehand sharpening.
I reprofiled the blade on a wooden dowel covered in Si paper from 350 -1500.
Then I went to the sharpmaker.
I think I may have messed it up there.
I may give up on this one knife and let the factory fix my mistake, its a bugger.

Pete - try this (humor it) quick trick - to strenghten the zt350 weak edge:

Take your 350 current edge

1) Bent wire/burr/softsteel over by scrape on a piece of balsa or cardboard start at 10* keep raising spine to about 90* with each scrape/strop stroke - scrape 2 or 3 times.

2) Use edge of DMT 8EF (use EEF if you want less toothy) with blade at bevel angle, use light pressure ~30 degrees walking forward movement edge-leading strokes to remove rolled wire/burr/softsteel. It usually takes 3-5 strokes depend on amt of pressure. repeat 1) for the opposite side. Expect a clean apex after 1 or 2 pairs of 1+2 steps.

Cut some cardboards. You will try & post the result, right

A slight recurve is not the problem, s30v is the bugger.

 

[Maniacal Pete]

Hi Blunt, I'll do jsut that and report back.
I also just realized that I really don't rely on the recurve part of the blade,
so I can learn to get this right sharpening just the belly and the tip on my diamonds.

 

[GatorFlash1]

Excellent. That's just what I needed to know. So after a few maintenance resharpenings, it'd be wise to re-set the bevel on 30 degrees, then 40 degrees for a hair-popping sharpness?

Depending on the steel it may take dozens of resharpening at 40 degrees before you have to rebevel at 30 degrees.

 

[Kamoe]

Currently it's a Benchmade 940 with a factory edge, S30V steel. If my research is correct, BM's edges are rather obtuse at 50 degrees or something similar. If I sharpen it with the Sharpmaker, even for regular maintenance, I'd be sharpening it at a different angle regardless, and I'm not sure if that's any good for the edge to have a partial-rebevel. So I'm probably going to have to completely rebevel with the sharpmaker once I get my diamond stones in the mail, since it'd probably take ages to do with the dark coarse stones and the white fine stones that came standard with the Sharpmaker.

 

[SunsetFisherman]

If you're cutting zip-ties with it I would highly recommend leaving the more obtuse BM factory edge in tact, those things will destroy an edge.

 

[GatorFlash1]

Currently it's a Benchmade 940 with a factory edge, S30V steel. If my research is correct, BM's edges are rather obtuse at 50 degrees or something similar. If I sharpen it with the Sharpmaker, even for regular maintenance, I'd be sharpening it at a different angle regardless, and I'm not sure if that's any good for the edge to have a partial-rebevel. So I'm probably going to have to completely rebevel with the sharpmaker once I get my diamond stones in the mail, since it'd probably take ages to do with the dark coarse stones and the white fine stones that came standard with the Sharpmaker.

One of the nicest things about owning knives with good steel like your and my BM's is the fact that you can sharpen them with smaller edge angles and still have a good long-term cutting edge. Some folks I know sharpen their BM with S30V steel to the 17 degree back bevel and a 15 degree primary bevel and have excellent long-term cutting success. You need something like an "Edge Pro" sharpener to get those kinds of small angles which are not much more than the angles of a straight razor.


Here is an article by Bladesmith Joe Talmadge, my knife guru, that may help to explain better what I'm referring to.

http://zknives.com/knives/articles/knifesteelfaq.shtml

 

[Forgetfull]

I've had a 940 and used the sharpmaker, bought the super ultra secret fine rods too, for a few years. It gets it really sharp (only issue I have is with the 1/2 inch tip section) but for some reason it doesn't stay like that for long.

I'd recommend doing a proper back bevel. Otherwise you're just fighting the geometry of the knife.

 

[Obsessed with Edges]

One of the nicest things about owning knives with good steel like your and my BM's is the fact that you can sharpen them with smaller edge angles and still have a good long-term cutting edge. Some folks I know sharpen their BM with S30V steel to the 17 degree back bevel and a 15 degree primary bevel and have excellent long-term cutting success. You need something like an "Edge Pro" sharpener to get those kinds of small angles which are not much more than the angles of a straight razor....

You're talking about 17°/15° inclusive? Seems awful thin, even for S30V. Or per side? If per side (30° - 34° inclusive), that's about double the angle of most straight razors, which are typically 15° - 17° inclusive (7.5° - 8.5° per side).

 

[Kamoe]

I already decided what I'll be sticking to with the Sharpmaker, 30° with a 40° micro-bevel will most likely do what I need out of the blade. My only question is, with the Diamond rods, how long will this reprofile take on the sharpmaker, going from Diamond > Coarse > Fine > Ultra Fine? How many passes would it take, or how would I know when I've completed the back bevel? I've heard getting a jeweler's loupe is a good way to check on an edge's progress, 30X magnification is probably enough, right?

Also I'm sorry with all of the questions, I just want to make sure I'm doing the right thing, I really don't want to trash a 150 dollar knife.

 

[Obsessed with Edges]

It's still going to take a good while, even with the diamond rods. S30V is notorious for it's abrasion-resistance, which is great from an edge-holding perspective, but also means it resists sharpening (by abrasion) as well. Thinning a thick edge in S30V is a project best undertaken with patience.

The only sure-fire way to know when you've reached the apex is to watch for burr formation. A good magnifier (10X or better) is a big plus for this, and use it under very bright light. Don't move beyond the diamond, until you've formed the burr from both sides.

 

[GatorFlash1]

You're talking about 17°/15° inclusive? Seems awful thin, even for S30V. Or per side? If per side (30° - 34° inclusive), that's about double the angle of most straight razors, which are typically 15° - 17° inclusive (7.5° - 8.5° per side).

I'm talking about per side., not inclusive, that would really be a razor. It is a very thin razor type edge that with many steels will require constant stropping/sharpening. With some of the steels in the RC60 range this thin edge will hold up an amazingly long time.

 

[Obsessed with Edges]

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