sharpmaker not getting the the curve

wudnme

wudnme

Joined
Apr 5, 2006
Messages
251
I have been using a sharpmaker for a while now and cannot get the curved part of the blade as sharp as the back or the straight part of the blade. when I draw the knife down the sticks I turn the knife tip down trying to keep the edge consistently perpendicular (At the proper angle of course). I can get the bottom of the blade to shaving sharp every time but, the curved end is not getting there.
 
Sorry, I misread your post: you're having a problem with the rounded tip of your blade.

You need to do a little wrist flick at the bottom of the grind. So as you bring the knife down the SM rod and pull the knife to you, towards the bottom of the rod you will need to move your wrist slightly to grind the tip of the blade. You still keep everything perpendicular, but it helps you to keep the edge on the tip against the rod. I think your problem has been that when you get to that tip you're not actually grinding the edge, but just the side NEAR the edge.

I've noticed that at least for me, some knives make me do this and some don't. I have a couple kitchen knives with an acute curve on the tip and I don't have to do anything special, but on my leatherman Charge blade I have to give it a little flick towards the bottom to really sharpen it.

Try a sharpie: blacken the cutting edge of the knife from heel to tip, and as you grind on the sharpmaker, look at the line to see what has been ground away or not.
 
I find that the longer the blade, the more difficult it is to sharpen the curved end. My tendancy is to pull the blade more horizontally as I end the stroke down the SM stones because I am nearing the bottom of the stones. This results in a cutting action near the tip that is more parallel to the edge than perpendicular. Try alternating your strokes, pulling from heel to tip (right and left sides) then pushing from tip to heel. It's a bit awkward at first but starting at the tip causes me to carefully focus on the tip. On the tip-first stroke, I generally don't go all the way to the heel. This technique works great for me on an old style butcher's knife with a long rounded end.
 
Hi, wudnme. I'm going to hazard a guess that the problem may simply be that that portion of the edge is still more obtuse than the angle of the Sharpmaker -- it is very typical of factory edges to be more obtuse near the tip.

Since the Sharpmaker removes metal pretty slowly, unless you've got the diamond sleeves, you may want to reduce the angle of the primary edge bevel where it isn't getting sharp using a benchstone or other faster sharpening method. Then go back to the Sharpmaker for finish sharpening.

FWIW, your technique of keeping the edge consistently perpendicular to the Sharpmaker rods is exactly what I do ... if you didn't, you'll be sharpening at different, unknown angles along different portions of the edge. Zeasor makes a good point, too, that you also want to keep the "stroke" from becoming too horizontal or parallel to the edge.

Also, because the Sharpmaker rods are relatively fine grit -- about 800 equivalent for the medium, 1200 for the white -- it does work pretty slow, and it's easy to start using excessive pressure out of frustration. This can easily weaken the steel behind the edge, making it hard to get a good edge, and poor edge retention, and also can round off the tip. So IMO either the diamond sleeves, or another means of sharpening that's much faster, is needed if a blade is really dull or has sustained some damage. The Sharpmaker is at its best as a touch-up or finish sharpener, using very light pressure to produce outstanding edges.
 
Might want to try the sharpie on the edge trick to see if, like Dog of War's idea, you are hitting the entire bevel.
 
I have also noticed that the portion of the blade near the tip sharpens more slowly than the rest on the Sharpmaker. I think that at least part of the problem is explained by the biomechanics of using the sharpener. Because of leverage, the force applied against the rods diminishes toward the blade tip if you are holding what feels like a constant amount of hand pressure throughout the stroke. That statement probably deserves more explanation, but I'll leave it at that for brevity. The most practical solution would be to just spend more time working on the tip portion of the blade and maybe be willing to apply a little extra hand strength there (within reason). It also makes sense to work the tip portion first, and once you have a burr there, work on developing it all the way to the tang. This is the reverse of what would be most natural. It will probably at least seem faster that way.
 
I've noticed the same as what Dog said. Most all my blades are more obtuse from belly to tip. It's normal to sharpen well from the hilt to the belly, then things go awry. Some of the problem is the way the blade is ground. The only knife (that I can think of at the moment) that is even ground from hilt to tip are my BM Nimravii.

You can't really see it, especially because most all manufacturers do such a good job grinding. My fix is to wrap the SM stones with wet/dry, starting at about 220 grit. Then tilt the end of the SM until the stone is at 25 degrees (in the 30 degree holes. Then grind the entire blade to 12.5 (25) degrees. You'll see that the secondary grind will appear wider from belly to tip. WHy? Because the primary grind was ground at a more shallow, or obtuse, angle at the factory, resulting in a secondary grind (edge) that is more shallow or obtuse. So when you re-bevel the edge (keeping the knife blade vertical), you are grinding more steel in that area. I haven;t re-beveled all my blades, and each blade is different, but all the ones I've done I can notice a difference in the secondary grind width.

If you use the sharpie-marker method as others have said, you'll see that you need to gently ADD a little angle from belly to tip. In that area, you're not hitting the edge.
 
I have the same problem. The sharpie will help. I think the problem is timing; getting the speed between stroke and angle just right.

Well,...it made sense when I wrote it the first time.
 
going to try the sharpie now. thanks to all for the input. Sounds like I have been expecting results to soon. The blade I am working now is a spearpoint on a camillus scout knife. I have had the same issue with all blades , toothpicks , clip blades on peanuts & barlows, etc. I like the Idea also of working from the tip backwards I may try that.
 
the only thing that worked was pushing it from the tip backwards to get that end of the blade sharp. I tried going r e a l s l o w. that didn't work. tried to concentrate on flicking my wrist down at the tip. that didn't work. the sharpie is a good idea , but not really necessary in my opinion on a sharpmaker. thanks again for the input.
 
Try practicing on knives you don't care about first.

To get the proper 'curve', I would suggest using a thin kitchen knife like a Chicago Cutlery blade until you get the right angles & turns down.
 
Another thing to watch out for on the Sharpmaker wrt getting the tips sharp is to avoid rounding the tips by letting the tips slip off the rods at the end of the stroke. To avoid this, one should end up with the tip gently resting on the plastic base.

Also, I sometimes find it necessary, especially on longer blades, to do some stroking that is just focused on the tips. In other words, starting the stroke near the tips and just sharpening the last inch or two of the blade, to get the tips as sharp as the rest of the blade. But in all cases, it is essential to avoid letting the tips slip off the rod which will cause rounding (and dulling) of the tips.
 
I just finished sharpening a Small Sebenza and focused on the curve.

I find that if start at the heel of the blade with the handle flat/square to the face of the stone and parallel to the surface of the table in which you have the Sharpmaker sitting on. Then move handle and blade on the same plain down and toward you until you get to the curve. At the curve let the blade drop more then the handle so the it will not parallel to the table and move the handle from the square position in relation to the stone toward the center of the "V" that the stones make. Continue the moving of the blade down and toward you as the handle goes up until the tip is on the stone. Do not remove tip from stone, this will round off pointy tip. I find that this gets the curve but doesn't get about 1/2" of the blade sharp from tip back.

Does this make any sense to anybody? Anybody use the same technique?

Maybe it will help the OP and I out.
 
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