Sharpening technical questions

[Emersonman91]

Hey guys I’ve been practicing and getting better with Spyderco sharpmaker and wanted to ask some technical questions to understand the concepts of sharpening


1)On a sharp maker when you have a 30° inclusive angle and a 40° inclusive angle what’s the point of the 30° back bevel angle I know it’s to put a micro bevel on the knife but what benefit does that give you. It seems as though if I just go from diamond to medium to fine on the 40° angle the knife is at shaving sharpness already.

why would I ever do the micro bevel 30° Angle


2)If you’re going to be doing both a 30° and 40° bevel do you do the back bevel first or do you do the primary 40° edge first

3) when sharpening is there some magical special perfect technique or is it literally just whatever gets you to the end result affectively and efficiently ? Because I’ve noticed I may be don’t match the angle of the sharp make her every time but I get a very nice crisp sharp edge they can shave hair almost every time.


Because I have a feeling that I am actually basically free hand sharpening using the sharpmaker because there are sometimes when I actually increase the angle or decrease the angle by laying the knife more or less perpendicular to the stone.


is this a problem or is it just whatever works


4) Regardless of what stone or set up that you use (Bench stone vs guided stones etc ) is the angle on a knife ever perfect to wear it will be a specific angle all the way through the knife because it seems like if I use guided stones like the sharp maker there’s always one spot on the knife the tends to not match up with the angle of the stone and you have to like maneuver the knife to fit or match the angle.

 

[tommytman]

1) it should cut better if you back bevel.
2) I don’t think it matters but I’d work the primary first. Then you can look at it and decide how much back bevel you need. Sometimes this back bevel is used on old blades that are getting thick. Then maybe you do it first to thin it out first.
3) your observations are on the mark. No factory edges are perfect . When you use the sharpmaker you will notice when that is the case. Unless it’s way off I try to match the factory edge by tilting the base of the sharpmaker with spacers to hit the angle I need as best I can.

im still a beginner , every blade I sharpen I learn something new.

 

[Craig James]

You can sharpen at angle you want (obviously the sharp maker only offers two) but typically the narrower the angle the better the knife will cut. There is a balance between sharpening angle and edge stability that depends on the task the knife is used for and the metallurgy.

traditionally your main bevel will be the lower angle (I.e 30 degrees) and the micro bevel the higher (I.e 40).

There are many different systems and techniques, all focussed on making the edge pointy and removing the burr, your micro bevel can be an aid with the latter. Some prefer micro bevels and some prefer not. Micro bevels are very prevalent in wood working where tradition and experience suggests 25-30 degrees (single sided) is perfect for a plane iron. People tend to sharpen at 25 and then micro bevel at 30 thereby maintaining performance of the primary bevel but reducing sharpening times.

Any type of free hand sharpening will yield uneven angles across the length of the blade, the degree of variation dependant on your skill level. This tends not to be an issue for most everyday tasks that you put a knife through

 

[bgentry]

The back bevel is 30 degrees inclusive or 15 dps. The micro is 40 inclusive or 20 dps. The back bevel is used to keep the blade profile thin. You don't have to use it, but a blade will tend to cut better with a thinner profile.

The micro bevel will eventually become the primary bevel if you sharpen at 20 dps constantly. Your edge will grow from a 1/128" wide micro to a 1/32" micro ....and on and on until you have a 1/8" wide 20 dps edge bevel. At that point the 15 dps primary edge is gone.

Using the 15 dps setting first helps keep that primary edge at 15 and keeps the blade thinner. If you intend to have a 15 dps primary, definitely use that setting first to develop a burr. Then use the 20 dps to apply a tiny micro to take the burr off.

Regarding "spots you can't hit" : This means the original sharpening was done inconsistently. OR it means that your use of the SharpMaker is inconsistent. A reprofile of your blade, using a sharpener that can remove metal faster than the sharpmaker, will make this easier to maintain.

If you have odd blade shapes like a Karambit or another blade with pronounced recurves, or large outer curves, the exact angles and replicating them become another story. For normal blade shapes a well profiled blade should be maintainable on the sharpmaker with almost no alteration to the intended motion. YMMV of course.

Sounds like you are doing a good job. Keep with it.

Brian.