get the longest lasting and sharper edge for slicing?

[Sir Joe]

Hi guys once again.

I am opening different threads so that all is easier to find for other users in the future (those who like me do forums searches before asking).

As I am in "buy mood" I was trying to understand if I should buy also the extra fine rods (or at least one, to save some money) for the Spyderco Sharpmaker.
My aim is max edge retention AND max possible sharpness.
The use is slicing, and I like when a knife is so sharp that just even with some pressure it cuts through, without need to move the blade to slice.
Kind of "laser slicing". If it sounds impossible, just take it as a aim, something I want to get as close to it as possible.
Materials to slice are: opening thick paper sacks of construction materials, opening plastic sacks (like those for gardening soil), slice cardboard, cut plastic, cut cords (not big cords which need a back and forward movement with a serrated blade. Just thin cords used to fix plants to poles to give them stability. I use to cut the cord with just a pull and it works of course well only if the knife is really sharp).

I have understood there are two schools: fine edge vs coarse edge.
I have understood that coarse/teethed seems sharper and can give a better draw slicing performance on some materials. I have not understood on which materials. I think that for the kind of materials I have listed above a fine edge should be preferred to a coarse edge, while for soft things (like meat, tomato) a coarse edge is better. But I am not really sure.
I have understood that coarse/teethed could become dull very fast because the teeth break. And for this reason some people say that a fine edge will stay sharp longer. But I did not understand if this is always or just on some steels.
Apart for this, I did not really understand much of when and why fine should be preferred to coarse.
It would be nice if you could explain that to me.

Anyway, apart for this specific use and on a more general basis I would like to know if the extra fine rod would give more sharpness and/or more edge retention, or when should one use them.

I thank you a lot once again, you are teaching me a lot!!! As also making me spend lot of money!!!

PS: I know I would have better results with a water stone or some other stone.
I am not ready to it but I will get to that. I see that sharpening is a medicine for the soul, much more enjoyable than I thought.
But for now, Sharpmaker.

 

[TravisH]

I prefer a coarser edge for kitchen work, especially for tomatoes.

For my kitchen knives, I just use the SM's Medium rods.

Slicing a tomato into tissue thin slices is just for showing off and TV commercials.

 

[Sir Joe]

Edited the tomato thing, I knew it would have been controversial
Yeah, I agree with you, that is how I leave my kitchen knives. The example was misleading, as I was asking for other kind of materials actually.

 

[HeavyHanded]

Thin and toothy is best if you're going to be pulling the edge.

If you expect to cut using a polished edge with pressure alone and on resilient materials, it needs to be thin and as highly polished as possible. If you prefer the SM rods, you might consider making a new block with the angles a bit more acute. 30° (not counting a microbevel) is as broad as any tool edge needs to be. One can often go thinner, say down to 26° and it makes a noticeable improvement in cutting, both pressure and draw cutting. Longevity will seldom suffer unless you push it into the sub 25° range.

Personally I stop at about 600-800 grit for most utility edges, and go to a higher polish for my choppers, be they my Chef's knife or a hatchet.

The extra fine rod gives a nice polished finish but still has a bit of tooth - not much though.

Keep in mind, the edge that performs a given task in a specified manner might not have the greatest longevity. You can get a highly polished edge to push cut sisal very well, but side by side a toothier edge used with a draw will out perform it in terms of longevity. Pressure into the edge is mostly what kills an edge, abrasive content of the material aside.

If a given material can be best severed with a low pressure draw, that's the better strategy compared to higher level of force needed with a polished edge. If the polished edge pressed into a material cuts it with less force than that will last longer than the toothy edge. You can force one or the other to perform reasonably well with a poorly matched cutting strategy, but longevity will usually suffer. This takes a bit of trial and error. That's why for utility I generally split the difference and use a medium/fine finish.

 

[David Martin]

A more coarse edge will slice for a longer time and gives a more utility edge. I sharpen mine on a Norton fine India and this edge will shave hair and slice tomatoes. DM

 

[Skimo]

Best for opening dirt and cement, working outdoors. Razor with replaceable blades.

If you insist, a cheap pocket knife can last until break or lunch, easily sharpened at low grit in short time.

Medium priced pocket knives, same, but make sure you have good synthetic or diamond stone to keep the sharpening time short.

Expensive blades, same as medium.

Step one, get a belt sander and thin the bevel, polish the bevel.
Step two, finish with a microbevel that's close to 15 DPS coarse, medium, fine or polished.
Step three, sharpen with coarse, medium, fine or strop as needed.

My personal advice, get a knife with super steel, M4 or stainless, and follow steps one through three. I know from my own experience steel like AUS8, VG-10 would last one day, steels like 154CM and S30V could last 4 days and M4 will last a week. Still, carrying a razor knife can greatly extend the usable time.

 

[Sir Joe]

You can get a highly polished edge to push cut sisal very well, but side by side a toothier edge used with a draw will out perform it in terms of longevity. Pressure into the edge is mostly what kills an edge, abrasive content of the material aside.
If a given material can be best severed with a low pressure draw, that's the better strategy compared to higher level of force needed with a polished edge. If the polished edge pressed into a material cuts it with less force than that will last longer than the toothy edge. You can force one or the other to perform reasonably well with a poorly matched cutting strategy, but longevity will usually suffer. This takes a bit of trial and error. That's why for utility I generally split the difference and use a medium/fine finish.

Most gardening tools are push or mix cut.
Pruners are almost 100% push. Shears are a mix. Hedge shears too. Snippers mostly push. Cord cutter (hook) push.
Than, knife: cement sack, ok, mostly slice. Cardboard my way and taste is push. Plastic sacks I like push: I stab them, lift the opening, and press the knife against the part to cut (which being lift is under tension). Plastic tubes is push.
From what I understood in this thread and with a side investigation on Spyderco forums, it seems that it may be I could go better with a really sharp tin very polished razor edge.
I always have two knives anyway, so I may leave the coming soon good one on razor, and the cheap one on coarse.
Do you agree?
About the Pruners, you say that a polished edge with too much pressure get damaged. Should I sharpen the pruners coarse?
Or wood is not a problem?

Step one, get a belt sander and thin the bevel, polish the bevel.
Step two, finish with a microbevel that's close to 15 DPS coarse, medium, fine or polished.
Step three, sharpen with coarse, medium, fine or strop as needed.
My personal advice, get a knife with super steel, M4 or stainless, and follow steps one through three. I know from my own experience steel like AUS8, VG-10 would last one day, steels like 154CM and S30V could last 4 days and M4 will last a week. Still, carrying a razor knife can greatly extend the usable time.

M4 and gardening are not good. I am relatively carefull with tools but not 100% constant. I may forget the knife (folder) wet and dirt of mud.
I was thinking of S110V and M390.
I am not friend of machines with high end and high price knives, free hand.
To reprofile I was thinking to start with a DMT extra extra coarse little one (120) or a Eze-Lap extra coarse (150) or a Lansky FP-1260.
The lansky is in this moment my best bet because it is double sided, 120 and 600. Seems like a wonderful way to sharpen things really fast.
Does anybody know if the Lansky things are ok?
Otherwise I have read good things of Eze-Lap and Dianova, but Dianova does not make extra coarse.
Of DMT I have read that the grid is not perfectly uniform.
Anyway, extra coarse on the protruding sides of the bevel, and than Sharpmaker with CBN.
Does it sound ok?

I do not understand the difference between step 2 and 3. Could you elaborate?
Besides, you say microbevel 30. I knew that mostly the bevel is 30 and the microbevel 40. Which I can do with the sharpmaker.
If the microbevel is 30, do I need to make the bevel 20?

Thanks

 

[TravisH]

DMT makes excellent products including double-sided stones. Check out their website - www.dmtsharp.com

 

[HeavyHanded]

Most gardening tools are push or mix cut.
Pruners are almost 100% push. Shears are a mix. Hedge shears too. Snippers mostly push. Cord cutter (hook) push.
Than, knife: cement sack, ok, mostly slice. Cardboard my way and taste is push. Plastic sacks I like push: I stab them, lift the opening, and press the knife against the part to cut (which being lift is under tension). Plastic tubes is push.
From what I understood in this thread and with a side investigation on Spyderco forums, it seems that it may be I could go better with a really sharp tin very polished razor edge.
I always have two knives anyway, so I may leave the coming soon good one on razor, and the cheap one on coarse.
Do you agree?
About the Pruners, you say that a polished edge with too much pressure get damaged. Should I sharpen the pruners coarse?
Or wood is not a problem?

My personal find is to sharpen pruners etc as a polished chop cut. If there is no lengthwise play, polish it up. Sometimes these sort of tool will benefit from leaving one side of the shear a little coarse so the material to be cut tends not to shift once the blades begin pressing, but a finer edge will overall cut best. In this case the coarse edge will require even more force than the finer one, polished edges carry less friction through the cut, especially on hard woody materials - this includes hatchets/machetes, anvil pruners and bypass shears (sometimes bypass shears can be left coarse one side). If no pulling/drawing action is a benefit, polish it up.

This follows along my kitchen knife strategy - anything that will be used against a cutting board - polish it up. Knives that will be used off hand and drawn through materials will be kept less refined.

 

[Sir Joe]

DMT makes excellent products including double-sided stones. Check out their website - www.dmtsharp.com

I own the Diafold coarse/fine.
I have just read that a guy somewhere claims that DMT's grit is not as uniform as Eze_Lap and Dianova.
Considering he named two different alternatives I do not think he has commercial reasons to say that. Which anyway does not mean he is right.
But I have searched and found Dianova products being very cool! I would have bought one because they are thinner than my diafold (which does not get well between the blades of a pruner), but when I found the Lansky foldable 120/600 I have decided for it, unless someone here tells me that Lansky is bad. If it is good, I go for it: it is thin, and onse side is very coarse, and I can use it for very fast sharpening or as first step of a reprofiling.
The only other super coarse little and cheap diamond sharpeners I have found are the DMT extra extra coarse (120) and the Eze_Lap extra coarse (150).
They both are one sided.

Sometimes these sort of tool will benefit from leaving one side of the shear a little coarse so the material to be cut tends not to shift once the blades begin pressing, but a finer edge will overall cut best.

Very cool trick! I will experiment with it as soon as I get the Sharpmaker!

But it makes me think that a Felco snipper which I just bought cheap has got a plain side and a somehow serrated side. The serrated is not really really on the cutting edge.
I should make a photo to explain but now I must go.

Cheers