Getting to the edge on the Sharpmaker

[bonesthedog]

I'm currently sharpening an old Benchmade 42 I had lying around, before I start on my 42MC.

I've been working the sharpmaker medium stone corners at the 40 degree settings, painting the edge with a sharpie, cleaning the stones when I feel them getting loaded with material, and I still can't reach the damn edge of the knife! What am I doing wrong? I'm holding it straight, applying little to no pressure, and keeping the knife perpendicular to the ground (should I curve it a bit because of the weehawk shape?)

I can't figure out why I'm not at the edge yet, the blade is 440C so it shouldnt give me as much trouble as I'm getting.

Ideally I'd like to invest in diamond stones to reprofile, but if one of you guys tells me to do the sandpaper trick, I guess I could do that too- not sure what grit to use for this task.

Thanks!

 

[he who say]

you need to start with a course stone, or sandpaper to remove enough material quickly, then finish with the sharpmaker.

 

[Jeff Clark]

If you are not reaching the edge you are not removing enough material. By using little to no pressure you protect the edge from damage, but you also slow down your rate of material removal. Until you reach the edge I would use higher pressure on the hones. I wouldn't push hard, but I would at least apply a medium pressure. Since you have inked the edge with a Sharpee you should be able to see when you have just started to hit the apex of the edge. At that point switch over to using the flats of your medium rods. Back off in pressure gradually at this point. Make sure that you remove all trace of the ink along the edge. At the point where all the ink is gone you should be using light pressure. Don't even think of using the white rods until the blade is sharp. I consider the 40-degree rod setting to be pretty obtuse. For an obtuse edge like that I would not use the white rods at all. You are better off leaving a little bit of roughness on your edge for more effective slicing.

 

[knarfeng]

you need to start with a course stone, or sandpaper to remove enough material quickly, then finish with the sharpmaker.

I agree. The Sharpmaker coarse stones really are not very coarse and do not remove material all that fast. They are for sharpening, not changing edge bevels. You want something coarser.

I use an old Norton Crystalon stone (silicon carbide) to change edge angles. Then I switch to a Norton Fine India (aluminum oxide). Once the edge angles are close to that of the Sharpmaker, that's when I switch to the Sharpmaker.

Some folks use sand[edit: sandpaper] over the rods for changing edge angles. I've not tried it, but I've been thinking about doing that next time. I've never done it cause I already had the Norton combo stone.

 

[bonesthedog]

Could I use an old water / oilstone sitting leaning up against the rods? Also, what angle should I be working on? 40 degrees the whole way?

 

[he who say]

yes you can, however i would just use the stone flat, and finish with the sharpmaker.the stone is mostly to remove enough shoulder to get at the edge.

 

[Jeff Clark]

Instead of leaning your bench hone against a rod I would prop the hone at an angle and hone horizontally (it is much easier). If you have an 8 inch long hone put something that is about 2.5 inches tall under one end of it to tilt the hone to around an 18 to 20 degree angle. Hold your blade horizontal as you hone. If your hone was only 6 inches long you would prop up one end with something that is about 1+7/8 inch thick.

Hone one side until you feel a slight burr begin to form on the opposite side of your edge. Then move your prop to the other end of the hone and hone until you feel a burr on the other side of the edge. Now you can go back to the Sharpmaker.

If it was me I would run lower angles for all this effort (although it is more work). I would use about a 2 inch prop under my 8 inch hone to do this edge profiling down around 14 degrees. Then I would use the Sharpmaker in the "30 degree" slots for most other work. Finally I might finish with a very few strokes in the "40 degree" slots to deburr the edge.