chisel-ground woes - some sharpening help?

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Jul 6, 2005
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i have no problems sharpening traditional blades. ive just gotten my first chisel ground tanto in the form of a used CRKT M16, and im having a little bit of trouble getting a shaving sharp edge on it.

i have a lansky system (with a coarse diamond for fast removal, and regular stones from extra-course to super-fine), as well as some strops for final finishing.
im having a few issues. the main edge was just a 30 degree grind, however the tip goes up to about 35+ degrees and then even higher at the point - 40 or so. im not so worried about this - if all else fails ill just grind the entire tip down to a uniform 35 degrees and be done with it (you can do this with a slightly modified lansky clamp). what i cannot understand for the life of me is why i can't get a proper edge on the main blade. it had a pretty dull edge so i worked down from course to superfine but it never even reaches shaving sharpness. there is no burr either.

is this due to the chisel grind? arent these supposed to be sharper due to the 0 degree angle on the other side? or could it be due to the lower quality AUUS-6 (or possibly even AUS-4 - some zytel handled M16s were made of this) steel? i can usually easily get a shaving sharp edge on an AUS-6 blade (i have a kasper KFF and companion that are both of the same steel), so perhaps it is a combination of the poor steel/chisel grind? perhaps a chisel grind is more suited to a higher quality steel?

suffice to say, ive never been a fan of tanto points and now that i actually own one thats chisel ground i am not impressed... i think ill stick to traditional drop and spear points - the tanto is a much bigger pain in the ass to sharpen, the left side grind makes precision work difficult for right-handers, and i honestly do not see much benefit in the tanto geometry - in fact i see the steel of the pointy 'belly' of the tanto eventually wearing down to the point where resharpening affects the geometry, and at that point itll just naturallly convert into a spear/drop point :)

so any tips on sharpening this thing with my current equipment? or should i just give up and leave it as a carpet-cutting/box-cutting/prying working edge and not worry about it?

cheers,
-gabriel
 
Don't have a lot of experience with chisel ground tantos but the few I've sharpened for friends had a much steeper angle than 30 degrees. If I remember correctly they were closer to 40 or 45 degrees. I'm guessing you haven't reached the edge yet. Try the magic marker trick or get something you can magnify the edge with to see what you're doing.
 
i worked down from course to superfine but it never even reaches shaving sharpness. there is no burr either.

Both of those should happen at the x-coarse stage. I would bet not enough metal is being removed.

With the x-coarse stone, achieve a full burr on the edge side, then grind it off flat on the other, repeat with finer hones as necessary.

i honestly do not see much benefit in the tanto geometry

There are some benefits (secondary point), there are also drawbacks and it is mainly a "tactical" look decision.

-Cliff
 
thanks cliff.
but for the life of me, it is not forming a burr. i am wondering if it might be the metal - some of the zytel M16s are actually AUS-4. could the 30° grind and AUS-4 be the culprit?
as for the magic marker test - i did that when i was working over it with the x-course stone, but i can also eye it and see that it is lined up with the factory edge.

ill give it another go from scratch.

cliff - since you are one of the authorities on the subject, so perhaps i can pick your brain on something...

with the lansky system, there are many types of stones available. you can get a set of diamond stones, regular stones, or arkansas stones. what are the benefits/drawbacks of each? i purchased the deluxe set of regular stones, but supplemented a coarse diamond for stock removal on hard blades. i believe it is nearing the time to replace a couple of my stones so im wondering if i should order diamond ones, stick with the normal, or try the arkansas ones.

also, i have problems cleaning the 'fine' stone. its just the standard type, so its a reddish ceramic stone. i always use honing oil as recommended, and clean after each use, but there are blobs of metal buildup on the stone that absolutely refuse to come off (i can take a photo if necessary). for this reason i usually avoid the fine stone, since the buildup seems to be affecting its performance and it is actually removing less than the white ceramic ultra-fine stone. is there a way to remove this? or is this normal? i only ever encounter this with this specific stone (the ultra-fine cleans off easily). this is one of the reasons i am actually considering switching to the diamond or arkansas stones.

mixing and matching is also a possibility: if you had to choose, say, 5 lansky stones from among them all, for an all-round sharpening set, which would you choose?

cheers,
-gabriel
 
Blackhearted said:
..it is not forming a burr. i am wondering if it might be the metal - some of the zytel M16s are actually AUS-4. could the 30° grind and AUS-4 be the culprit?

The angle doesn't really matter, I have never yet seen an edge which won't burr, I have seen a lot that will burr and that is all you can do, the edge just cracks apart. You can't do much with those except put a very rough utility edge on them, sometimes a file will succeed where a coarse stone fails.

as for the magic marker test - i did that when i was working over it with the x-course stone, but i can also eye it and see that it is lined up with the factory edge.

There only needs to be a hint of the edge not being ground to induce total failure, if you can check it under magification, just 10x will do, you can see if it is cracking or crumbling at the edge. If this is the case, return it, it is defective.

If you are so inclinced, since we are both in the great white north, you can drop it in the mail to me and I can have a look at it. Turn around time should be under two weeks with regular mail, which will cost just a few dollars as a small packet.

...a set of diamond stones, regular stones, or arkansas stones. what are the benefits/drawbacks of each?

I have not used the lansky hones, but in general abrasives have fairly common properties.

The only drawback to diamond is that you can tear the diamonds out of the plates if you apply too much pressure , the edge pro has the same problem which is why Ben Dale doesn't heavily promote diamonds for the edge pro.

Now you can make an arguement that since diamonds are more expensive than decent man made hones and that those hones can get very similar in terms of cutting speed (or even higher if you use high pressure), that diamonds hones are not worth the cost.

Many knife makers will opt for japanese or norton waterstones, and the Norton SiC/AO india stone is another very popular choice because of this and some of them think diamond hones are just a waste of money. I like them on knives which need to be hones with very light pressure.

Arkansas stones are vastly inferior to most quality man made hones in regards to cutting speed. I have a nice black one which I use some times to put on a final edge, when I am feeling nostalgic, but I have various waterstones which cut faster and will leave a more consistent finish.

is there a way to remove this?

Just work the stone on some coarse sandpaper to recut the surface. If the surface glazes over competely, the stone will just act like a smooth steel.

-Cliff
 
thanks.. i guess ill stick with the regular hones then.

as for cleaning up the fine stone, ive tried the sandpaper approach before on it, and it has worked a little - of course i didnt do it too vigorously for fear of 'ruining' the stone. unfortunately this particular stone just seems to clog up way too quickly, and is difficult to clean. it might just be the natuure of the stone or perhaps there were low spots there and thats why it is filling up so badly.

ill give it a more vigorous working over and post on how i fared.

how do you feel about chisel grinds? unfortunately unlike emerson, CRKT (and benchmade it seems) chisel grinds are ground from the lefthand side of the blade - because this is the same side as the logo and it looks better for promo pics. ive tried precision work with it and its a little awkward because the edge is 1/16" to the right of where i expect it to be, and it also has pretty weak results sharpening stakes with strokes away from the user. i could see it being more useful if it were sharpened on the righthand side.

perhaps in the end i will get frustrated with it and just regrind the whole thing into a spear point... however that will present a new problem since the tip is machined at a slight offset to compensate for the fact that the edge is only on one side. all in all a very wierd experience altogether with my first chisel-ground tanto.. i can see the benefit of the geometry for prying, for example, but it just seems like way too much maintenance for me. once that second 'point' starts to wear down the entire geometry will be compromised and itll start to be a quasi-drop point anyway. i am lucky this is an inexpensive knife, and my first tanto wasnt a $160 benchmade, i wouldnt have been too pleased. as it is itll make a neat little project, and be relegated to an extreme abuse knife :)

cheers,
-gabriel
 
I had the same problem with my M16 and thought that the steel was not able to form a burr. I used a diamond stone and persistance paid off. Once I ground the edge enough, it finally formed a burr. These were chisel ground, but not tanto blades.
I was trying to finish with a ceramic rod and found that I just dulled the blade. I used a steel and got much better results.
I was sharpening one for a friend and mine, too.
On the second blade, I received my new Edge Pro. What a difference. I gave the Lansky to my neighbor.
 
Blackhearted said:
as for cleaning up the fine stone, ive tried the sandpaper approach before on it, and it has worked a little - of course i didnt do it too vigorously for fear of 'ruining' the stone.

You can't ruin a stone in that manner, most stones need to be flattened on a semi-regular basis anyway to keep them nice and even on the surface.

how do you feel about chisel grinds?

I see little use for them in general and would prefer a symmetrical grind.

i could see it being more useful if it were sharpened on the righthand side.

Yes it needs to be matched to the hand bias of the user.

...once that second 'point' starts to wear down the entire geometry will be compromised and itll start to be a quasi-drop point anyway.

Yeah I have seen a lot of well used ones which ended up with a smooth arc eventually.

-Cliff
 
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