Reprofiling/Sharpening CPM 3V?

[Cliff Stamp]

...if I place lets say a penny under one side it will make something lets say .5 degrees less but on the other side because it is much farther away it would only make the stone .25 degrees less

Flip the Sharpmaker around so the distance/elevation is the same. This is an old technique for producing a multi-bevel/angle Sharpmaker, people have even calculated the exact thickness of wedges required to get exact angle increments. There was even a guy selling them, some kind of hardwood shim, graduated in 0.5 degrees. There are even fancier ways like little inclines which work on set screws, but if you are going to go that far I think you might as well throw away the Sharpmaker and just make an adjustable rod as it is just as simple. However I have said for years if Spyderco just added an adjustable leg set up to the Sharpmaker it would make it far more versatile as you could just turn a screw by one rotation for example to increase the angle by 0.5 degrees (or whatever).

[Brock O Lee]

I reprofiled my Tuff to 30 with a 40 deg micro bevel, but on the Edge Pro. It took me about 40 mins, using the 120 grit SiC stone to do the bulk of the work.



CPM-3V feels similar to CPM-S30V, with similar grindability from what I remember.

The challenge is that the Tuff is quite thick behind the edge, so you have to remove a lot of steel. I have tried to reprofile thinner blades with the SM diamonds, and it took me way too long, so much so that I gave up and just freehanded them using coarser DMT's.

It would not be impossible to use the SM for this task (diamonds or CBN), but it will not be my 1st or 2nd or 3rd choice!

[Surfingringo]

Isn't the coin trick flawed in the fact that the stones arent centered on the base so if I place lets say a penny under one side it will make something lets say .5 degrees less but on the other side because it is much farther away it would only make the stone .25 degrees less

No, it doesn't matter where the stone is connected to the base. If you change the angle of the base by 1 degree then any vertical rod attached to any point of the base will be tilted 1 degree.

[Surfingringo]

I own a Spyderco Tuff and I am a bit worried about how much abrasion resistance the CPM 3V steel possesses and that it will be very hard to sharpen or reprofile.

The diamond /CBN rods are very coarse similar to a ~400-500 grit stone and they will cut any steel at the same speed, it doesn't matter if it is 3V, VG-10, or 1095, all of them (carbides and all) are buttery soft compared to diamond and CBN. This means that the steel doesn't make any difference, you would grind the Tuff with those rods no different if it was 3V or VG-10.

However, how you grind is critical as it has a many-to-one difference on the speed of the grinding and the wear on the stones. Here is how you do it effectively :

-use a lubricant on the rods, water will do, ideally add a small amount of detergent, really ideally use an actual cutting oil

-mark the edge in black

-grind on the 20 dps setting until the marker it almost removed right to the edge

-use only enough force to make it cut, this isn't very much at all

-go as fast as you are comfortable, this is likely faster than anyone you have seen grinding

-don't go right to the edge, the knife doesn't blow up if you do, it just wastes the steel

-don't take the knife off the stone, cut up and down

-rinse/flush the stones off once the marker is removed

-mark in the edge again

-put a coin under one side of the sharpmaker, this will decrease the edge angle by ~1/2 degree on the rod nearest the coin

-grind on the 20 dps setting (now about 19.5) until the marker is almost removed right to the edge

-this is only a tiny angle change, it will happen very fast

-flip the coin, remark the edge and repeat on the other side

-continue this adding coins (or something similar) until completed

There are many reasons why this is much faster than doing one slogging session. It is precisely because people ignore basing grinding techniques that a lot of people think this is way harder/more difficult than it needs to be.

Plus people tend to grind really, really, really slow. It is very easy to make two passes (up/down) per second, I normally do between 4-6 per second and that is cutting both up/down, however you might want to work up to that, but 2 passes per second is easy to get.

If you employ a little technique then resetting the edge on the Tuff from 20+ dps to 15 dps won't take you half an hour. If you practice that technique a little and use a coarse benchstone vs the rods, you could flatten / zero the primary grind in similar time.

Note at very high grinding speeds, 4-6 passes per second, there will likely be a little rocking of the bevel, it will end up slightly convex and you run a high risk of scratches on the main blade grind. Again, you might want to work up to that.

--

In short, the steel doesn't matter, grinding techniques are critical. And yes I have done it on many knives including 3V, 10V, 121REX, Maxamet and not only changed the edge angle but flattened entire blade bevels on knives which had thicker cross sections.

It isn't difficult, it doesn't require much skill or effort, just a little knowledge and it can be done far quicker for example than you could change a flat tire or other similar basic activity.

In fact if you actually read this post, then it is likely you could have had the first marker session completed by now.

Cliff, I am interested to know why the technique you outlined would work faster than just grinding away at the 30 degree setting? I can't figure that one out as it seems like you will ultimately be removing the same amount of material. Is it because you are making contact with a larger area on the stones?

Also, I think I have to disagree with you about a harder steel grinding just as quickly as a softer one. Yes, I know that diamonds are harder than either but the hardness will indeed affect how deep the diamonds cut. Sand is harder than any wood but that doesn't mean oak will sand at the same speed as balsa.

[Nate]

Cliff, I am interested to know why the technique you outlined would work faster than just grinding away at the 30 degree setting? I can't figure that one out as it seems like you will ultimately be removing the same amount of material. Is it because you are making contact with a larger area on the stones?

Also, I think I have to disagree with you about a harder steel grinding just as quickly as a softer one. Yes, I know that diamonds are harder than either but the hardness will indeed affect how deep the diamonds cut. Sand is harder than any wood but that doesn't mean oak will sand at the same speed as balsa.

Cliff can also reply, of course, but I thought this snip explains the "why" pretty well:

"In filing, or grinding in general, you want to maximize the pressure you apply at a given force. Chris talked about this which was where I heard it and it made perfect sense. What you do is apply a layered bevel, essentially you always work the corners of the bevel you just formed. The difference is pretty dramatic in terms of cutting speed. Now if you have a high power grinding, water cooling, and 36 grit SG belts you don't care about any of that, you just use a holder block and ram the steel against the belt and watch it melt off like water."

[Ankerson]

I reprofiled my Tuff to 30 with a 40 deg micro bevel, but on the Edge Pro. It took me about 40 mins, using the 120 grit SiC stone to do the bulk of the work.



CPM-3V feels similar to CPM-S30V, with similar grindability from what I remember.

The challenge is that the Tuff is quite thick behind the edge, so you have to remove a lot of steel. I have tried to reprofile thinner blades with the SM diamonds, and it took me way too long, so much so that I gave up and just freehanded them using coarser DMT's.

It would not be impossible to use the SM for this task (diamonds or CBN), but it will not be my 1st or 2nd or 3rd choice!

That's what I was talking about, more how much steel would have to be removed. :spyder:

[paladin]

Isn't the coin trick flawed in the fact that the stones arent centered on the base so if I place lets say a penny under one side it will make something lets say .5 degrees less but on the other side because it is much farther away it would only make the stone .25 degrees less

If you're in the Northern Hemisphere just keep the short end of the base pointed toward the North Pole and switch sides of the table as you sharpen opposing sides of the blade...the increased curvature of the Earth's surface as it slopes toward the Arctic corrects the base length problem, BUT that only works if you're using Canadian Loonies...

Nevermind, I'm sure the sharpening guru's have their slide rules sliding, laser transits shooting, plumb bobs dangling working on this so-called "flaw" you've seemingly uncovered.

BTW, 4-6 up/down per second (albeit, a short cycle) is an impressive stroking rate...it must take years of dedicated practice to reach that jedi-like level

[Cliff Stamp]

I am interested to know why the technique you outlined would work faster than just grinding away at the 30 degree setting? I can't figure that one out as it seems like you will ultimately be removing the same amount of material. Is it because you are making contact with a larger area on the stones?

There are two reasons, a sensible one and a stupid one, Nate noted the sensible one and it is easy to see if you take a wood rasp to the corner of a 2x4 and make a few passes and then :

-continue on that flat

vs

-keep alternating on the corners produced

But again, it is all the steps of the technique which work together to produce a result which can be staggering and allow you to achieve in minutes what people can struggle with for hours. This sounds so dramatic there is almost a suspension of belief it could be true however just consider :

-most people only grind on the down stroke, if you go both ways you cut 2x as fast

-most people don't use a cutting lubricant and work with clogged stones

-the layering effect will significantly increase cutting speed for reasons noted

-the grinding speed for most people is as low as half a pass per second, it is easy to grind 4X that fast

If you multiply these together you have a grinding speed which is easily 25X as fast as most people work.

Now as for the stupid reason, it is because your brain is dumb, but relax, everyone's brain is dumb so we are all in the same train. If you grind on the flats then nothing happens for a long time, this will really distort your sense of time because you are comparing nothing against nothing. However if you grind on the bevel facets then each session is literally 1-3 minutes, in fact you have almost just finished marking/coin setting and you need to do it again. You can also clearly see the bevel dropping each time and each stage makes immediate and practical improvement.

There is no need for example to continue past 19.5 dps to see an immediate improvement as the knife will now apex on the 20 dps setting immediately which means the ease of sharpening has improved dramatically. But if you grind on the flats then nothing really productive happens for a LONG time which is again why most people don't do it as they think it is a long involved task and if you don't do all of it then it makes no difference. But if you break that up into say 10 smaller tasks then each one looks easy, and if you apply the above grinding techniques then it really is easy and you do it and wonder why anyone would ever be concerned about it as it takes as much time to do one set as it does to get a coffee.

Also, I think I have to disagree with you about a harder steel grinding just as quickly as a softer one. Yes, I know that diamonds are harder than either but the hardness will indeed affect how deep the diamonds cut. Sand is harder than any wood but that doesn't mean oak will sand at the same speed as balsa.

Oak has a Janka hardness of ~1500, Balsa has a Janka hardness of ~100.

A really hard knife steel will have a hardness of ~65 HRC, a really soft one has a hardness of ~55 HRC

To a first approximation, abrasive wear depth (and speed of cutting) is modeled by the Archard equation (if you are in the US, otherwise it is typically named after Reye's) which noted that wear depth is proportional to 1/H where H is the material hardness. Thus relative depth would be H'/H, or the hardness ratio. As woods have a very high relative hardness span then abrasive depth can vary significantly, not so much with steels (1500/100 >> 65/55). Most steels in fact span a hardness range of just +/- 2 HRC (60/58 ~= 1).

Now you might say - well wait now, how come then sharpening 62.5 HRC 10V on an Arkansas stone is so slow but sharpening 60 HRC O1 is very fast? Well that is because Archards equation assumes that the abrasive particle isn't influenced by the cutting. This is a good approximation for diamond, not so much for quartz which is grating against vanadium carbide. In that case two things happens :

-the wear reverses and the vanadium cuts into the quartz
-the rounded/worn quarts stops cutting and starts rubbing/ploughing

and the equations get a lot more complicated as there is now plastic deformation, rubbing, three body wear and the solution to all of them is that stone isn't a good choice go use a harder abrasive so it returns to the Archard condition where the math is easier (and the cutting more productive).

[JD Spydo]

Do you think the diamond stones would at least make it bearable?

No, the geometry is just too thick, would take you FOREVER.

Wow! Ankerson I love your posts and usually agree with you 95% of the time but this one has me scratching me head in total confusion :confused:

I will admit that I have not yet sharpened any blade made of S3V so I guess I''ll have to somewhat give you the benefit of the doubt. But I have sharpened many other blade steels inlcluding ZDP-189 ( on dozens of occassions), S90V, D-2 ( even on a custom made blade), XHP, and many of the other exotic blade steels used by the Great Spyder FActory.

I have two great diamond benchstones>>> one is a coarse NORTON 220 grit and the other is an extra coarse 90 grit benchstone made by 3M company. Both stones have monocrystalline diamonds which I've been told are the best for sharpening, deburring and other abrasive uses.

I've never failed to reprofile any steel with those stones as well as a couple of DMT stones I have>> so I find it hard to believe that I couldn't reprofile a blade made of CPM 3V. Why wouldn't high quality diamond benchstones not work on that steel?

[Ankerson]

Do you think the diamond stones would at least make it bearable?

No, the geometry is just too thick, would take you FOREVER.

Wow! Ankerson I love your posts and usually agree with you 95% of the time but this one has me scratching me head in total confusion :confused:

I will admit that I have not yet sharpened any blade made of S3V so I guess I''ll have to somewhat give you the benefit of the doubt. But I have sharpened many other blade steels inlcluding ZDP-189 ( on dozens of occassions), S90V, D-2 ( even on a custom made blade), XHP, and many of the other exotic blade steels used by the Great Spyder FActory.

I have two great diamond benchstones>>> one is a coarse NORTON 220 grit and the other is an extra coarse 90 grit benchstone made by 3M company. Both stones have monocrystalline diamonds which I've been told are the best for sharpening, deburring and other abrasive uses.

I've never failed to reprofile any steel with those stones as well as a couple of DMT stones I have>> so I find it hard to believe that I couldn't reprofile a blade made of CPM 3V. Why wouldn't high quality diamond benchstones not work on that steel?

He was talking about doing it on a Sharpmaker. :)

[JD Spydo]

OK Ankerson I didn't get the context of that>> Sorry I overlooked what you were talking about initially. I guess my brain has "Monday Morning Syndrone" today :o

And you're so right on there because even the diamond rod on the 204 Sharpmaker is not all that coarse as I would like it to be. I have heard that S3V is one mean blade steel for sure and I'm looking forward to getting something made with it.

Yeah diamond benchstones ( the good ones that is) are much more aggressive that the rods on the 204 Sharpmaker. I've lobbied many times for some more coarser stones for the 204. I've yet to get the CBN rods but I'll probably get them when I get my tax refund. And that's the only real gripe I've got against the 204 Sharpmaker is that it's really only geared for finishing work per se.

Which is why I'm looking very forward to this new Spyderco GAUNTLET sharpening system coming down the pipeline. Sorry I overlooked that you were mainly referring to the Sharpmaker>> I knew something didn't sound just right on the surface.

I think I would prefer a fixed blade made with S3V myself but I may give a 3V folder a try at some point.

[Ankerson]

OK Ankerson I didn't get the context of that>> Sorry I overlooked what you were talking about initially. I guess my brain has "Monday Morning Syndrone" today :o

And you're so right on there because even the diamond rod on the 204 Sharpmaker is not all that coarse as I would like it to be. I have heard that S3V is one mean blade steel for sure and I'm looking forward to getting something made with it.

Yeah diamond benchstones ( the good ones that is) are much more aggressive that the rods on the 204 Sharpmaker. I've lobbied many times for some more coarser stones for the 204. I've yet to get the CBN rods but I'll probably get them when I get my tax refund. And that's the only real gripe I've got against the 204 Sharpmaker is that it's really only geared for finishing work per se.

Which is why I'm looking very forward to this new Spyderco GAUNTLET sharpening system coming down the pipeline. Sorry I overlooked that you were mainly referring to the Sharpmaker>> I knew something didn't sound just right on the surface.

I think I would prefer a fixed blade made with S3V myself but I may give a 3V folder a try at some point.

Yeah. LOL :D

I believe the Sharpmaker is a great tool, I have had mine going on 20 years now.

But it's my belief that taking on something like the Tuff being as thick as it really is there are better options for taking it on in a reasonable amount of time even with the Diamond Rods.

[Cliff Stamp]

Yeah diamond benchstones ( the good ones that is) are much more aggressive that the rods on the 204 Sharpmaker.

The diamond rods on the sharpmaker are very narrow, hence the pressure on them is very high, very coarse diamond/CBN rods made in the same way would very likely suffer from tear out. It is possible to make diamond/CBN stones which have sufficient strength for such rods but you have to use different bonding processes such as brazing. I have such commercial diamond abrasives used to cut granite for example which are graded down to 30 mesh, the abrasive is so coarse you can see the individual grains, however you really would not want to see that in the Sharpmaker and I guarantee whoever is running customer service for Spyderco would not either.

[paladin]

He was talking about doing it on a Sharpmaker. :)

yup...and that's why I advised against it also...

Plus the OP never initially mentioned how steep he wanted to take his reprofile which brought the blade geometry into being a possible issue-- the Tuff has a pretty serious thickness behind the edge... :) :spyder:

[bdblue]

How close can the primary angle be to 20 degrees and still allow the Sharpmaker on 20 degrees to easily sharpen the secondary bevel? Maybe the OP doesn't have to reprofile all the way down to 15 degrees per side. Maybe he could set the Sharpmaker on 20 degrees with the diamond stones, and shim the base to get to 18 degrees or 17 degrees and reprofile that way. This could make the reprofiling quicker.

[Cliff Stamp]

How close can the primary angle be to 20 degrees and still allow the Sharpmaker on 20 degrees to easily sharpen the secondary bevel?

As long as it is under it, the finest graduations are usually seen on guys working chisels who take sharpening seriously as they do so much of it when they work with the more exotic woods. Graduations of 1/2 a degree are common and that is all that is needed to effectively make the next bevel a micro-bevel. Now they are using jigs so the angle control is high, essentially you just need to be above whatever slop you have on the Sharpmaker.

But again, as noted in the above, if you are using the diamond rods on the Sharpmaker and changing the angle is a long/daunting process, you are simply doing it wrong, there is a technique to grinding efficiently just as there is to anything else. The diamond rods are for example much more coarse than the stones Murray Carter uses for sharpening and he doesn't just alter the edge bevel angle, he alters the blade bevel angle with them.