CPM 440V sharpening

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aero_student
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CPM 440V sharpening

Postby aero_student » Tue Sep 04, 2001 12:00 am

I have knives of ats55, aus6 and cpm440v. I can't seem to get the cpm as razor sharp as the other two steels. Is this normal? Do you guys (and gals) have any tips on sharpening it? Thanks

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Postby The Stare » Wed Sep 05, 2001 12:43 am

I'm no expert on sharpening, but a couple facts stand out. The surface you're using to sharpen the steel must be harder than the steel, or it's components. CPM440V has a lot of vanadium carbides in them. They are harder than typical man-made benchstones. Ceramic rods are usually harder than the vanadium carbides, but not a whole lot. Takes a lot of time.

You may need to get diamond-based sharpeners to get 440V to the razor sharpness you desire. There are relatively inexpensive little diamond pocket hones. Benchstones are more expensive.

It is important, if possible, not to let the 440V steel get as dull as you may be accustomed to letting other steels get before sharpening them. Check them and touch them up when they begin to dull.

Stare

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Postby Zoro » Sat Sep 08, 2001 4:32 pm

You are not alone with have problems with the 440v I too have the same problem the 440v steel knives. I know that I might be alone with the thought that 440v steel is not for me I like the VG-10 steel better.

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Postby yog » Sat Sep 08, 2001 6:23 pm

Hi Zoro.
I think CPM-440 and VG-10 both have their place.
I might be wrong, but it seems to me like CPM-440 is a coarser grained steel, which makes it very good on rough work knives like the Military. But for a small pocket razor I will now always try for VG-10, the edge seems to polish up (fine sharpen) better.

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sal
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Postby sal » Sun Sep 09, 2001 9:38 am

Hi guys. Some thoughts to share.

Abrasion resistance means the steel doesn't want to release (give up) molecules. The more abrasive resistant a steel is, generally the longer it will stay sharp and the harder it is to sharpen. The same ingredients and features that make it hold an edge, make it harder to sharpen. Period.

There is no such thing, IMO as a steel that is easy to sharpen and holds and edge well. It's "salesmen's talk". Edge geometry can help to improve sharpening speed by being thin but all in all, the edge retention and sharpening are going to be similar.

CPM-440V, in all of our tests will hold an edge longer than VG-10 by a certain percentage and it takes that percentage longer to get the very fine edge on CPM steels.

Course diamonds (300 mesh) will help "rough in" the edge faster, but only VERY FINE diamonds can approach creating a very fine edge.

sal

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Postby mundele » Mon Sep 10, 2001 1:37 pm

Will these "very fine" diamonds be the ones used on the upcoming sharpmaker diamond sleeves/rods?

--Matt

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Clay Kesting
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Postby Clay Kesting » Mon Sep 10, 2001 2:36 pm

I've found that the trick to getting a fine edge on CPM440V is to finish sharpening with a number of very light strokes on the white rods. Doing this I have no trouble getting the knife to shave. The process used to make CPM steels produces a very fine grain structure but it does seem to need extra care to find the edge hidden in the steel <img src="wink.gif" width=15 height=15 align=middle>. You can find out more about the CPM process here http://www.crucibleservice.com/.

Clay

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Postby The Stare » Mon Sep 10, 2001 2:43 pm

Sal -- I'm sure you're right to a large extent so far as manufactured blades and stock removal blades.

I still believe that expert forging can indeed create a steel that will cut with 440V and yet sharpen very easily. Have spoken withe maker I mentioned earlier. He indicates he is too busy at present to provide a knife for your CATRA machine, but still sounded quite interested in giving it a try. Kinda sounded like he would relish surprising you. I hope I can persuade him to send you a knife in future.

Stare

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sal
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Postby sal » Mon Sep 10, 2001 7:48 pm

Hi Stare. A forged blade that is differentially heat teated has to be harder that a file at the edge and soft at the spine (ABS rules). Considering that a file is generally about Rc72, logic would tell you that it would be harder to sharpen than a softer steel, all other things being equal?

In addition, most guys that forge blades do their final edge on a buffer, not a stone. Some of them actually use the 204.

Hi Matt. No, we'll be using something to profile with. Probably in the 300 - 325 mesh range.

Once a blade is profiled well, the white stones will do a great job. CPM just takes longer and needs lighter strokes towards the end.

sal

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haji
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Postby haji » Fri Sep 14, 2001 11:09 am

I sharpen about 50 knives a week, on average, and I found one trick that yields a really good, polished edge on all steels, even my Starmate. After restablishing the bevel, usually on a belt sander, I hone the blade further on either the 204 or some version of the Crock Sticks. Once the edge is sharp enough to cut paper, I polish it on a steel, in this case, a Henckels 9" steel that we have on sale for $9.99. The steel puts a very polished edge on the knife, and in using the paper test a second time, I find it routinely allows the knive to cut paper much smoother. You can feel how much less drag there is on that paper. For the first three or four months I owned my Starmate, all I did was buff the edge on that steel, and within 10 or 15 strokes it was back to a really sharp, polished edge. If you haven't tried this, give it a shot. You may be pleasantly suprised.

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Postby kjellmusic » Sat Sep 15, 2001 3:17 pm

I love CPM440v and although it might take a bit longer to remove lots of steel you won't have to do that very often.
I use the Lansky diamond sharpeners and when I first get the knife I take the factory blade edge down till I get a smooth angle on the lansky. The fine diamond stone really brings out a serious edge on 440v and from there you can just touch it up as it dulls with the fine stone.
I like an edge with a bit of tooth but smooth too, I don't polish my edges beyond fine diamond. Tim Zowada wrote an article on his preference in sharpening (which I believe is the same as mine), which allows for the micro-serrations to do the cutting work. Sometimes it helps if the blade actually grips the material when it is cutting.
Anyway, I have found that CPM440v really takes a nice edge that way.
The white ceramic sticks are also great for quick touch ups that won't scrape up the edge.


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Postby Ken A. » Fri Sep 21, 2001 4:18 pm

I was wondering why my CPM 440V blade was not getting any sharper after using a Lansky Deluxe knife sharpening set. As it turns out, I was committing a very basic error. I took a broad point Sharpie marker and marked the bevel to the edge. After a few strokes, it was obvious that I wasn't sharpening the edge but was grinding a slightly new angle to the bevel. This was not obvious with the naked eye. DUH!

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4 s ter
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Postby 4 s ter » Fri Sep 21, 2001 8:44 pm

I've been using a the "Sharpie marker" method and a magnifying glass recently to ensure I'm actually sharpening my knives rather than just reprofiling the bevels. It DOES work and my knives are sharper than I've ever been able to get them before. (I get some funny looks - but sharper blades)

Dave


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