3 basic questions about sharpening

L

learnme

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Oct 30, 2009
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1. When do you know it is time to move on to the next level of grit? Are there any indicators?

-I ask this because I can work on the diamond side of my DC4 indefinitely without ever knowing when I should move on to the ceramic side. The same goes for all levels up till 0.25 micron.

2. IS there a difference between pushing and pulling during sharpening? What do you do?

-I ask this because for the longest time I believed that only pulling throughout the entire sharpening process was the best approach. However, there was a burr on the edge that was so big it glinted when placed under light. I tried and I tried but I couldn't get that sucker. Eventually, I decided to try pushing. All it took was a few passes and now that thorn in my side is gone. Logic tells me that pulling is the way to go, but this recent development has left me wondering.

3. Is there a way to maintain an angle? OR something to use as a guide? Or even know the right angle for your knife?

-(Used Pulling method ie. on leather) I ask this because I am right handed and have the desired angle on the side that is going from left to right/top to bottom, but when it comes to the flip side, right to left/bottom to up I really screw things up. I know this because on my practice knife the side that contacts during L>R strokes has a distinctly larger edge than the side that contacts during R>L strokes.

Answers,Advice, you know the drill, learnme pls. Thanx


Oh and 1 more...

What is thread testing?
 
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Go to the sticky thread on F A Q at the top of this forum, read, practice, then come back with questions.
 
1. When to move between grits. The only sure way to know that you are "done" with a particular grit is to feel for the burr. When the burr forms, you are done with that grit. A more subtle indication is that the "feel" of the blade on the stone changes as you polish it. Essentially, you'll reach a point where it stops feeling rough and feels the same on every stroke. At that point, you've polished it as much as that grit is going to polish it. I think the burr is more reliable.

2. Push versus pull strokes. In terms of metal removal, they are the same. In terms of polish they are the same. In terms of burr formation, pull strokes form more burr (bigger and easier) than push strokes. If you think of the metal as being something more like clay, then this makes sense. Pulling allows the metal to "stretch out" behind the edge as you stroke. Pushing tends to ball the metal up, but it still forms a burr; just smaller.

3. Holding a constant angle. If you are free handing there are a few hints:

A. Watch what you are doing. Memorize the "look" of the blade at the start of a stroke, so you can do it that way every time.
B. Find somewhere on the stone, knife, table, or some combination that gives you a tactile (feel) reference. This can help to maintain a constant angle.
C. Be sure to raise the handle as you go through the curve of the blade! Very important.

When freehanding you can use various guides. The most simple is a wedge. I use a folded up piece of paper. Fold the corner of a piece of paper. Magically you have a 45 degree angle. Fold it over again. Now you have a 22.5 degree wedge. Others here have cut blocks of wood, using a protractor, so they have various angles to use as references. Important: when using these references, make sure to do (A) above: *Look* at your blade when it's at the correct angle. Memorize the look and try to duplicate it on every stroke. Check with the reference every few strokes.

Still others prop up their stones on various objects at precise angles and then run the blade across them perfectly parallel to the ground (or table), to maintain a constant angle.

The DMT aligner and other clamp on guides can help you maintain a VERY constant angle. I haven't used these, but they are mostly highly praised here.

Thread testing: Not exactly sure, but I recall something about some people using thread (like you sew clothes with) to test their edges. Something about trying to slice a free hanging thread or something.

Hope that helps some.

Brian.
 
I've used and posted some results on thread testing. Basically, you have a thread under tension, and run your edge along it to see how much edge you need to cut it. Let's see if I can't dig up some old pictures to illustrate. I'm going to test a couple of Spyderco Mules in M4 and S90V soon to see how they stack up, at the request of a fellow forumite, and I'll use the thread to measure my results.

p2.jpg

p1010582.jpg
 
If you want to keep you angle the same when sharping use the larger muscles your legs not your arms. Place your blade on the stone of choice at the angle of choice and instead of trying to move your arms and keep this angle, use you legs to move your whole body holding your arms and the blade at the proper angle. It's too easy to change angles as you move your arms closer and farther away the angle changes and a flat edge is sharper than a rounded one. I know convex lovers will not want to hear this, but it's true.
 
Thanx guys, I have sharpening down now, if your interested you can read about it here.

I will make a poll though about edge leading and edge trailing just to see what most are doing and why. Thanx again and happy sharpening.
 
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