M4 and Spyderco Sharpmaker/KnivesPlus strop block

[CryoGuy5272]

I did a search and while I found some good info, not much leant itself to my particular situation. I am having some difficulty getting my Gayle Bradley back to stupid sharp using my stock Sharpmaker and strop block. Used it today to cut some pretty tough insulation off of some electrical service wire, and while it is sharp, its not where I would like it to be. Anyone have any tricks or techniques that may be useful to get it back to that stupid edge I know its capable of taking?

 

[DeadboxHero]

How dull is it? Any pictures?

 

[CryoGuy5272]

It will still slice copy paper decently. My camera doesn't have a high enough resolution to show anything that would help. Toward the tip I am able to get it very sharp, hair popping if you will. But the closer to the heel I get the duller it gets. It will only scrap up dead skin at the point farthest back toward the heel. When stropping I noticed what feels like a burr on one side but nothing on the other, and I can't get it to smooth out. It is pronounced enough that it raises the knap of the leather. I thought maybe I was just making strokes against the grain, so I turned the strop 180 and still got the same result.

 

[cbthedookie]

I've found my sharp maker issues generally came down to two problems:
1) not spending enough time on coarse rods to get good apex
2) alternating strokes which prevented building a definitive burr (and corresponding consistent apex)

I'd start fresh, work one side coarse to get a burr, switch sides and repeat and knock off burr. Repeat with fine rods. Your blade should be very sharp - easily cut paper - at that point.

If you've done that, you could be rounding/dulling on strop. If so, work carefully to get correct angle (20 degrees off sharp maker) and use light pressure while stropping.

 

[Danketch]

I found one of JDavis's videos on using the Sharpmaker to complete rock my world and re-evaluate the system. I cant find the video now, but he keeps the blade on one side of the stone, and moves up and down the stone without moving the blade off of the stone, until he gets a burr along the whole edge. This has really helped me with using this system, including on my Gayle Bradley. Might be worth a try.

 

[Obsessed with Edges]

It will still slice copy paper decently. My camera doesn't have a high enough resolution to show anything that would help. Toward the tip I am able to get it very sharp, hair popping if you will. But the closer to the heel I get the duller it gets. It will only scrap up dead skin at the point farthest back toward the heel. When stropping I noticed what feels like a burr on one side but nothing on the other, and I can't get it to smooth out. It is pronounced enough that it raises the knap of the leather. I thought maybe I was just making strokes against the grain, so I turned the strop 180 and still got the same result.

Most knives' primary grinds will be thicker towards the heel of the blade, especially in the radiused 'plunge grind' area just forward of the ricasso, where the edge grind transitions outward to the ricasso/tang of the blade. On flat stones, or on the flats of the SM rods, that transition area will also lift the stone/hone away from the edge as the edge of the stone 'rides up' that radiused transition in the plunge. The edge grinds on most will also usually be more obtuse (wider) from the factory, in that portion; might be outside the 40° limit of the SM in that portion, or very nearly so. Making things more difficult, the edge in that portion is only in contact with the hone for a fraction of a second (at the very beginning of the stroke) in a heel-to-tip stroke. The combination of all those factors means it's very, very common for that portion to take much longer to sharpen up, especially after the factory edge grind's apex has dulled. Using diamond or CBN rods with your Sharpmaker can speed up the process.

Stropping 'against the grain' of a leather strop usually won't make any difference with anything but very fine burrs; it shouldn't matter which direction you strop on the leather. The heavy burrs need to be minimized on the stones/hones first, most of the time. More aggressive strops of denim, canvas or linen, over a hard backing (wood, glass, etc) used with aggressive compounds like white rouge or other aluminum oxide compounds, can do a better job with heavy burrs if removing them on the stones isn't done beforehand.


David