Best way to thin a super thick edge?

tknife

tknife

Joined
Mar 18, 1999
Messages
9,966
I got a Ontario kukri that I wanted to keep in my truck and use for chopping and such. But the edge is way too thick. I did a little chopping, and it cuts about as well as a brick. I tried reprofiling with a diamond hone, but it seems that it will take the rest of my life to accomplish anything this way! Is there a faster way that will not ruin the temper?
 
A few ideas to try by hand :

1) a quality very large bastard file. Clamp the blade in a vice and lean into it with the file.

2) a large x-coarse waterstone and x-coarse lapping compound (40 grit or so). Spread the lapping compound on the stone and use a lot of pressure.

3) large sheet of x-coarse sandpaper. Can be used like a strop, or on a flat backing like a hone. Get metal working sandpaper, the cheap wood working quality won't do much of anything.

All of these are much faster than a diamond hone, but you are still looking at hours of work to thin out a really thick edge on a large knife.

If you have access to power equipment, then you can grind without overheating by taking one pass at a time, and cooling in water after each pass. Don't press too heavily, or move slowly as these will allow to much heat to build up. Working with your fingertips on the blade gets solid feedback. Even something like an angle grinder will do to get the rough shape. You then refine it with a file and or hones. Sharpening blades in this manner is fairly dangerous if you don't know what you are doing, so take care, wear protection, etc. .

Personally though, I would not spend the time as Ontario's QC isn't that great in my experience. You would probably not be that happy after a few hours of work to get the blade in shape, if it then got heavily damaged during use. Just check out a recent example of this type of failure with this exact same blade :

http://www.bladeforums.com/forums/showthread.php?s=&threadid=201739

They do make decent blades on occasion though, so hopefully you got lucky.

-Cliff
 
Use a file or a belt sander. If you use the sander, use a coarse grit for roughing the blade down. Don't over-heat the edge.
 
Thanks Cliff, I know you have done plenty of reprofiling in your tests. I did quite a bit of chopping on some preasure treated 2X4's and various seasoned firewood, and am fairly confident that the blade isn't brittle. I will give the grinder method a try and try and get a lot of metal off quickly, and then do the finer grinding with various sandpaper grits.
 
Just to reiterate a point Cliff has made elsewhere: don't take down the angle too much at once, or you risk ruining or compromising the blade. Take it down to an angle still above what you believe is optimal. Test and reprofile till you start to notice micro-chipping or rolling (a 8x-12x loupe or magnifier is really nifty here). Bring the angle back up a little, and it should be optimized for maximum chopping/cutting without losing edge strength.

Removing too much of the bevels at once, and you'll need to remove quite a bit of the edge to restore it, esp. if you chip out a big piece. Besides, by gradually taking down an angle, you'll get a chance to see first-hand (as I've learned) how significant an increase in performance you get by even small modifications. So don't worry about how long it might take: the greatest gift is the knowledge learned along the way; the optimized edge is simply a reward, and representation, of the wisdom gained. It's simply more fun, and more educational, to take the long way.

My .02 --

Glen
 
Through away that Khukri and get a HI BAS, or WWII, or Sirupati, or whatever! They are all excellent! Thick? = yes. Sharp? = yes Guaranteed for life? = yes Cut through anything? = yes

Why would you want a thinner blade? That would tend to fracture out in the field. Get a thicker blade that just keeps it's edge better, IMHO.

my 0.02
 
You must log in or register to reply here.
Back
Top