Help needed. Knife won't sharpen...

G

godogs57

Joined
Apr 16, 2004
Messages
795
Is this a stupid question or what? I finished a knife yesterday and the damn thing won't sharpen. Anybody ever have one of those days? It is a new design of mine...sort of my interpretation of a fillet knife. 10" overall, 6" blade. ATS-34 @ Rc of 60. It being a fillet knife, I finished the blade just a tad thinner than my usual hunting knives. At completion, I went to the flat platen and whupped on a 20 degree angle, finished it up with my diamond stick, did my usual shaving test on my arm and the dang thing felt like I had rolled the edge (Had not though)...it just skated over the hairs! Uh oh.. Back to the flat platen/diamond stick and re-set the angle at about 17 degrees...same story. Back to the platen/diamond stick @ about 22-25 degrees...same story. I settled @ 20 degrees and finally got a shaving edge, but not "scary sharp" as I am accustomed to ...just barely shaving. I will not sell the knife just yet, if ever, as it sure seems peculiar as to the angle it likes. Most of my knives like the 20 degree angle...a lucky few could care less and will split hairs at whatever angle I put on them. I guess it is just part of making handmade knives versus the cnc machined, assembly line stuff from factories.

In making some knives early on, I remember always having the toughest time putting an edge on the thinner blades that I made for some reason...just wondered if anyone else has this problem and what they did to solve it.

Best regards,

Hank
 
Maybe has to do with the blade flxing during sharpening, making the angle more obtuse than measured?
 
Perhaps....anyway, this is about to cause brain cramps for me trying to figure it out....does not happen often, but when it does, it burns me.

Thanks for your suggestion!
 
did you knock the burr off of it..... strop it with some chrom oxide on a thin leather glued to a piece of pine...

it'll shave.....


;)
 
After setting the initial angle, I can 99 3/4% of the time get a scary sharp blade with the fine grit diamond sharpener or crock sticks...have yet to make a strop, but will get one now.

This is embarrasing..........
 
I had the same problem about the time I first started. Finally dawned on me that the blade never got heat treated.
 
As the only knife shop in town I get to sharpen a couple hundred knives per year. The ones that wouldnt take an edge were softer steel.
 
Hate to say it, but yep, its an Rc of 60....I dunno...I guess stuff like this just happens. A gunsmith buddy of mine who makes super accurate custom rifles in South Carolina says in his business, sometimes one of his creations just won't shoot to his standards for no apparent reason....nothing is different, it just won't shoot. Perhaps something like that is the case here....crap happens. Oh well.....
 
If it's HRC60 then it should hold and edge. Is that HRC60 at the edge or spine, ricasso, etc.?

If the edge is hardened, cut a piece of wood the shape of the blade and use it as a backing when on the belt and buffer. Use something on the order of 120/220, followed by 320/400, Then remove the burr with a felt wheel loaded with green SS compound, holding the blade at 45 degrees for a quick pass, followed by another pass at about 25-30 degrees. You don't have to push hard here, just two quick passes. Repeat on the other side. No need for crock sticks. Use the wood still, as backing on the buffer. If that doesn't make any difference, then...................???????????

Like was said above, the blade might be flexing
 
You might try going to a slack belt convex edge. Finish it off on a buffer like Mike said above. I use what the jewelers call a razor wheel with some 5µ diamond paste for a quick cut of the wire edge.
Sometimes the wire edge is hard to get off, so I cut some hardwood along the grain to help it along before finishing on the buffing wheel
 
When this scenario occurs it is usually the result of the edge getting overheated in the finishing and polishing,The blade may be RC60,but the edge may be RC48.It only takes a split second to heat it to 500-600 and ruin the temper on the edge.An edge flex test may confirm this.
 
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