While sharpening, I like to feel the edge by running three fingers into the edge in a shaving motion to feel sharpness and also in a stropping motion for feeling the burr, shave hair, cut paper, look at it under a light for reflectivity, etc. All these things can show up imperfections and spots then need more work. Example, if you slice paper you might find a spot on the edge that grabs and tears from the remains of a dent, chip or burr on the edge.
If you are not satisfied with the way a knife cuts scallions then that is a pretty good (or the ultimate) test and shows it is not sharp enough. Sharp has many definitions but in the case of a knife it is generally accepted that it means the two bevels of the edge come together and terminate at a point (or line if considering the whole edge). After the two bevels
bisect at the edge the next step is to refine the finish of the two bevels.
You may be asking the wrong question. A slightly different twist is how do I get a knife sharp and when do I stop sharpening?
While sharpening a knife (free hand, on a Sharpmaker, belt grinder, or any other sharpening gizmo) you know when the two sides (bevels) have met when you form a burr. Did a burr form when you were sharpening this knife? If not you never brought the two sides together. You either need to take more metal off at the current sharpening angle in which case you probably need a coarser grit to save some time, or increase the angle to get to the edge quicker taking off less metal. Work with the coarsest grit you have (the diamond stick, brown sticks, or wet & dry sand paper over a set of the sticks until a burr forms. If you need to remove much metal then 80# wouldn't be to coarse. If a burr doesn't form with a few strokes I would move to a coarser grit. You could get coarser grits as mentioned before, using wet & dry sandpaper laid over the sharpmaker sticks. Trying to reprofile with the fine sticks could take longer then you are willing to invest and is probably a waste of time.
How coarse to start with can be a judgment call or it will become a matter of trial and error. The file idea would be good for reprofilling if you feel comfortable with free hand holding angles. If you do you probably don't need the Sharpmaker and you could achieve the same results on a coarser bench stone free hand. You would also then have the advantage of being able to progress through coarser to finer grits with a series of stones like 150, 500, 1000, 2000, 4000#, etc. Unfortunately the Sharpmaker only has two grits (three if you have the diamond sticks) both of which are in the middle to finer end of this progression.
You may be sharpening on the shoulder of the bevel and not getting to the edge at all. This could be because the Sharpmaker doesn't match your factory bevel angle and you are working hard to change the angle but have not gotten to the edge yet. Again did you get a burr all the way along the edge?
It this case, you are trying to change the angle that came on the knife to match the Sharpmaker (reprofile), and that happens to be one that is more acute (shallower) then what was already on the knife and it will take a lot of work on any of the Sharpmaker sticks. They are too fine for that. The Sharpmaker is not the best tool for this but coarser grits will help. Coarser is you friend here. If you want it to go faster you could also use a steeper angle. The 20° per side (40° inclusive) setting will go a lot faster then the 15° setting and is not a bad angle for a lot of knives. Any knife is not going to be very robust at 15° (30° inclusive). If they are already at 15° I would use that setting especially for a light duty knife you want to cut like a razor like a paring knife. With the edge at 20° the 15° setting is great for reducing the shoulder (making a compound bevel). Probably should state what kind of knives we are talking about in order to decide what angles are appropriate, but keeping the angle near the way it came or steeper and or one that also matches the Sharpmaker will be a lot less trouble. For soft kitchen knives (most of them except Japanese knives) 40° inclusive (the 20° setting) would probably be about right. For really hard knives or knives that will be used appropriately (not chopping and twisting on a cutting board) a more acute angle may be appropriate. You might be surprised how sharp a knife can be at even a 60° inclusive bevel.
Find out how you are doing with respect to whatever angle you chose on the Sharpmaker by marking the edge (bevel) with a Sharpie or Magic Marker. Take a stroke or two on the 15° Sharpmaker setting and see if it takes the marker off all the way to the edge. If it is just working on the shoulder try the 20° setting. To expedite reprofiling as much as possible use the setting that is greater then or closest to the factory angle. 40° inclusive on most knives will be very sharp and cut scallions just fine and hold up a lot better then 30° inclusive against a cutting board, etc. If you want to change the the bevel angle I suggest getting it sharp at the angle closest to one on your Sharpmaker first and consider changing it later after you know how it works when it is sharp at the original angle. I think you will find that is the 20° setting (40° inclusive) on most knives.
So, I would say
the first question is, did you get a burr? Don't stop sharpening with the coarsest grit you decide to start with until you form a burr on both sides the full length of the blade. Next, reduce pressure and continue with light storkes until the burr is gone. Go to the next lower grit and repeat this process and refine the scratches and remove the burr you get with each subsequent finer grit. Like someone said earlier, after you get a burr on the brown sticks and remove it the blade will be shaving sharp. It will just be more refined with the white sticks or other finer grit.
For bench stones I like my Shapton Glass synthetic Japanese water stones which are a synthetic stone made from ceramic particles bonded together by some kind of binder. They wear more then Sypderco ceramic stones, but I think they offer the best compromise of wear and fast cutting. You can lap and flatten them and you can't do that with the Spydercos which are not always flat from the factory. The
Norton combo stones 220#/1000#, 4000#/8000# are fairly cheap, pretty complete with 4 grits and they work. The 220# one wears too fast, dishes and the feel could be better on the fine ones but they are a great set for learning freehand on. I don't like diamond plates for finishing (in the fine grits) and like water stones better. The DMT's like the D8XX, D8X, and D8C are great for the coarse grits and reprofiling though. Most here seem to like DMT's, other diamond plates or Spyderco ceramic stones all the way to finishing. Final finishing with a leather strop loaded with stropping compound adds a lot to most knives. I wouldn't bother on soft kitchen knives but if you really get into it you probably will.
This is where I get my Shaptons and DMT's.
Here is another place for the Norton's with the flattening stone and instruction DVD.
Have you read
this? It is a great place to start.
Gary
