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Uneven knife grind

Started by Trevlett, January 13, 2013, 12:33:27 AM

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Trevlett

Hey guys,
Had my T7 a while now and love it for my turning tools but I've ran into an issue with the short knife jig. It's the first time I've used the knife jig so maybe I'm doing something wrong ( iv read the book and watched the vids!)
I'm getting an angle change when I flip the blade over! One side ends up getting a wider grind edge than the other?
Any ideas?
Many thanks
Trev

Mike Fairleigh

Is it a thick blade?  If so, you could call it a known issue.  If you look at how the knife jigs are designed, they clamp from only one side - the other side is fixed.  So the thicker the blade, the further offset the edge is from the center axis of the jig.

I've gotten pretty good at sharpening my woodworking tools on the Tormek, but the basic task of sharpening knives remains the most challenging to me.
Mike

"If I had 8 hours to chop down a tree, I'd spend 7 sharpening my axe."  --Abraham Lincoln

Rhino

I agree.  Sharpening knives remain challenging to me too.

To say again what Mike said.  The jig is designed for a knife of a certain thickness.  If the knife being sharpened is thicker, or thinner, there will be a slight difference.

One solution:  Don't worry about it.
For my day to day knives, I don't care so I just sharpen them like that. 

Second Solution:
I suppose if I have a knife whose looks I really cared about, I can sharpen one side.  Remove the knife from jig, flip the knife, mount the knife in the same position on the flip side and sharpen the other side.

Third solution:
Measure the angle separately.  Move the rest up and down depending on which side you are sharpening.  Or make a paper sleeve from a sheet of rolled paper and tape, have the sleeve on or off the rest depending on which side you are sharpening.

Fourth solution:
Learn to sharpen small knives freehand on the tormek.  It is not as demanding as it sounds.  It is a small knife and doesn't take that much time to do.  And you only have to be consistent for a small time - since it is a small knife.

For me, the first solution is the best.

Mike Fairleigh

I've recently bought two fairly high-end Becker Ka-Bar knives.  They both came from the factory with an uneven grind.  Yet, I'll probably never be able to keep them as sharp as they came because they were that sharp.

I really think with knives, freehanding is the only true solution.  Too bad I suck at it.
Mike

"If I had 8 hours to chop down a tree, I'd spend 7 sharpening my axe."  --Abraham Lincoln

Jeff Farris

Mike,

To get better at it, get your grindstone super smooth with the grader, turn it around so the wheel is turning away from you, get a drawer full of cheap knives and start working. The more you do, the closer you'll be to perfection.

Of course, the same thing can be said for doing it with the jig.  :D
Jeff Farris

Mike Fairleigh

Thanks, Jeff.  If I can scrounge up some cheap knives I'll do that.  These Beckers are very thick, enough that the grind is really obvious if the jigs are used.  As well made as the jigs are, I'd sure like to see them come out with a self-centering version.  Even with a lot of freehand practice I'm not sure how anyone can grind repeatable angles that way.
Mike

"If I had 8 hours to chop down a tree, I'd spend 7 sharpening my axe."  --Abraham Lincoln

Herman Trivilino

Quote from: Trevlett on January 13, 2013, 12:33:27 AM
I'm getting an angle change when I flip the blade over! One side ends up getting a wider grind edge than the other?
Any ideas?

Is it possible that the angle is the same one side is wider than the other because you spent more time grinding that side?

Just spend more time grinding on the other side until they match.
Origin: Big Bang