Trouble getting my final edge on the blade

SkagSig40

SkagSig40

Joined
Feb 1, 2001
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I recently started making knives and I noticed that all of my final bevels/cutting edges keep coming out with a slightly rounded convexed edge. It is shaving sharp but I'd like to learn how to get a nice sharp V edge that is flat at the cutting edge and not rounded. I'm guessing it is my 400 grit flexible belt and the 400 grit gaiter belt I was using to sharpen. How do I accomplish this? Also curious how you guys do your final sharpening. What belts and techniques do you use?

Also is it safe to set up my work rest as a jig to hold the blade at say a 20 degree angle for final sharpening? It seems I can only get it to work edge up and I'm worried the cutting edge is going to cut into the belt, grab and get thrown from my hand. Any help is greatly appreciated!!! Thanks!!!
 
I grind final bevels edge down, freehand. The flattest bevels I can get from a belt are with the mylar belts, I use 30 or 40 micron. They are thin and do not compress like cloth belts, so there is less convexing. But I think there will always be a slight convexing when done on the belt sander.

I tried to sharpen a knife edge up once, on a 10" wheel. The edge caught the wheel, cut the belt, and luckily was thrown into my water bucket and not my gut or feet. I don't think this is necessarily as big of a concern in a jig using belts on a platen, which has less give than my rubber wheel, but I won't ever do it again that way, without a reverse function so the belt turns away from you anyhow.
 
kuraki said:
I tried to sharpen a knife edge up once, on a 10" wheel. The edge caught the wheel, cut the belt, and luckily was thrown into my water bucket and not my gut or feet.
Click to expand...

That ended a lot better than it could have.
 
I tried to set up my articulating work rest from Northridge so I could sharpen edge down and it was kind of tight and I did not have a lot of room between the work rest and platen. Even with it edge down it kept grabbing the blade and throwing it down. Confused and scared the crap out of me! I'll try the 30-40 micron mylar belts. What brand and where do you buy them at? Many thanks!
 
Make sure you are sharpening at he recommended angle, That is why the words "per side" and "inclusive " are used by many of us. A blade with an edge angle of 30 degrees is sharpened at 15 degrees per side. If you did it at 30 per side, you would have a 60 degree edge ... which is what a hatchet has.

The other common problem with a new maker is an edge too thick before sharpening. The edge should be nearly a sharp edge at around .005" when you sharpen a knife. I take mine to a zero grind and then sharpen. After HT, you have to sand the whole bevel down from the .030" pre-HT thickness to .010" for a heavy duty blade, and .005" or less for a cutter/slicer.

Rounding of an edge is often a problem with people using a slack belt or hand sanding with the paper folded up and no backing block. It should be done on the flat platen or with a hard sanding block and paper until it make an almost sharp edge, then the edge put on.

Another common new maker issue is people who sharpen on stones. If you don't hold the blade at a very even angle the whole stroke, you can create an edge that increases as it approaches the apex. Rapidly rocking the blade up and down a waterstone will make the same rounded edge.

I do not like using the work rest as any angle grinding jig beyond something like a 45 degree spine or mune.
You are far better off to do the final edge by hand. Obviously, down is far safer. With practice .... and variable speed ... you can do it up or down.
 
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Ok so correct me if I am understanding this wrong. I liked to use the spyderso triangle sharp maker to touch up blades and I think it is a 40 degree total angle(20 per side). So when I hold the knife so it is straight horizontal, edge down on the stone, that side of the edge is being sharpened at 20 degrees. It this correct?
So I set my work rest at 20 degrees using my I-phone angle gauge and sharpened the edge facing up. It did not grab at all. It only grabbed when going edge down. I'll see if I can get pictures posted.
 
I also use a Lanski with the guide rods to set a blade to 20 degrees. The guide says 20 on each side. I want to get away from those methods because of time and learning correctly how to do this on my grinder and free hand with stones.
 
Learn to freehand on your grinder. As was said, variable and reversible each add a bit of ease of use. I learned to sharpen edge up. I recently did a poll on edge up vs. down sharpening on the TKG facebook group, and it was about 2/3 edge down.

Stacy's advice about being thin enough prior to sharpening is important.
 
i use the lansky also for final sharpening. i do not think you can get the edge as flat as the lansky freehand. it would be nearly impossible to hold it at the exact angle with every pass. to speed things up, i get a burr on each side with 220 grit belt freehand, then go to the lansky. for the final step i took an old lansky stone, glued on a piece of leather slightly larger than the stone, rough side facing the blade. i rub some white compound on the leather and stop away from the edge. everything stays pretty flat.
 
OK, I was a bit random on my edge comparison. I changed it to be more accurate.

40 degrees is and OK angle for a field and camp knife ... as long as the bevel is properly thin. I personally don't do many edges above 30 degrees inclusive ( 15 per side).
 
I was going to say. I do quite a few field/camp knives at 20 DPS and have no complaints. I tend to go 10 DPS in the kitchen, 15 DPS on a hunter or other cutter, 20 DPS on a rough use knife or chopper.
 
If you want a perfectly flat edge, then you need to finish on Lansky, Wicked Edge (or clones) or Tormek. I find paper wheels are a fast, relatively easy way (easier than stones) to get a good, sharp finished edge, but it is not completely flat. Doesn't need to be.
 
SkagSig40 said:
Ok so correct me if I am understanding this wrong. I liked to use the spyderso triangle sharp maker to touch up blades and I think it is a 40 degree total angle(20 per side). So when I hold the knife so it is straight horizontal, edge down on the stone, that side of the edge is being sharpened at 20 degrees. It this correct?
So I set my work rest at 20 degrees using my I-phone angle gauge and sharpened the edge facing up. It did not grab at all. It only grabbed when going edge down. I'll see if I can get pictures posted.
Click to expand...
That is correct. What I have found to be the easiest way to sharpen on a grinder is if you have an adjustable platen. Set the platen to whatever angle you're wanting. If you want 40 degree edge the set the platen to 20 degrees. Hold the knife, edge down, at 0 degrees or perpendicular to the floor. Make a few passes and switch sides. Nathan the machinist made a holding fixture that hangs from the ceiling to keep his blade straight up and down which I plan on doing at some point. I start with a fresh 220 j flex and end with a worn 400-600 depending on the knife. Then buff or strop once you have a burr along the entire edge.
 
Once I got over my initial fear of doing it and dorking up a knife, I do it how Matt describes. With the addition of a Surgi Sharp leather belt and green compound sharpening is fast and easy. I still make a couple hand strops after the leather belt, but I don't know if it's even necessary.

I love the Surgi Sharp belt. The burr on things like Z-Wear or 3v and the like were taking me forever to strop away by hand.
 
I've only been making knives for about 3yrs and the easiest quickest way I've found for final bevels is using my flat glass platen, edge down, start with 120 g J-weight belt to start with, then go to 320g, 600g, then on to Trizact 30 micron, 16 micron, and finish with close to a polished edge with a 6 micron. Comes out hair shaving sharp. Not sure what the final angle is but so far it seems to work and has been the most consistent for me...
 
Bubble Jig, edge up. Accurate, repeatable and no chance of snagging. That only happens if the angle is changed.
 
I don't know why I didn't think to recommend Fred's Bubble Jig ... itv solves these problems and speeds the learning curve.
 
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