Sharpening problem

P

Ptrkgrgr

Joined
Aug 20, 2020
Messages
14
Hello guys. Today i finished my blade from o1 tool steel. It is 6mm thick 25cm long knife. I tried to sharpen that knife but I can’t make burr. I was sharpening with Lansky sharpner, 20° angle but i just can’t sharpen that knife. What can be problem? Blade seems to be hard. After heat treating i did file test. File couldn’t properly scratch the steel. I did about 20 strokes. After that i tempered in kitchen oven 200°C for two hours. Can it be too hard and bridle Or what do you guys think? Thanks for any advice.
 
I'm sure more will follow, but details about the knife would also help

How wide is the blade

How was it ground? full flat, hollow, saber?

How thick behind the edge do you have?

A pic would also be handy too of the blade.

G2
 
Pretty aggressive blade you made there, quite the fighter !

Looks like the edge bevel may be thicker and your sharpening hasn't gotten both sides to really meet up yet, hence no burr. I would say give it some more sharpening taken care to watch for it to meet up and produce the burr you need.

1B1E4A21-C87D-426E-BB2E-8BC78D46A59F by Patrik Griger, on Flickr

G2
 
i spent today about 4 hours with sharpening. I will try tomorrow and i hope you are right. Thanks for your help
 
Angle the blade towards a light so you can follow the bevel that you made so far with your sharpener and see if the bevel is uninterrupted or if it’s faceted which would indicate that it doesn’t go all the way to the edge
Also looking down on the edge with a strong light and look to see if you see anything along the edge

good luck with your work
G2
 
Mark the bevels with a black sharpie so you can see where you are removing material from the blade and where you need to remove more.
Are you using the diamond stones or the regular stones?
 
Ptrkgrgr said:
Hello guys. Today i finished my blade from o1 tool steel. It is 6mm thick 25cm long knife. I tried to sharpen that knife but I can’t make burr. I was sharpening with Lansky sharpner, 20° angle but i just can’t sharpen that knife. What can be problem? Blade seems to be hard. After heat treating i did file test. File couldn’t properly scratch the steel. I did about 20 strokes. After that i tempered in kitchen oven 200°C for two hours. Can it be too hard and bridle Or what do you guys think? Thanks for any advice.
Click to expand...
That's barely enough heat for a sun tan.
The heat treatment requires O1 steels to be slowly preheated to 649°C (1200°F) and then heated at 788-816°C (1450-1500°F). Then these steels should be held at the same temperature for 10 to 30 minutes and finally oil quenched.
 
Yes that temperature 200°C 392°F was tempering temperature. I am pretty sure that steel is hard enough if not too hard. And i use marker to see where i am removing material all the time. But I don’t understand I have been using coarse (i think 60grit) stone on Lansky sharpener for good 4hours and still no bur there. I measured bevel and it is under 0.3mm. Maybe it is really not enough sharpening because steel is too hard?
 
A Lansky system will be slow going on such a large knife. It would be best to fully establish the edge on the belt grinder at 120 grit and then refine it with the medium and fine stones. I prefer taking the edge to near zero (almost sharp) on the grinder and then sharpening it. If that isn't helping, then the issue may be that you are looking for something that is not there. The burr may be worn away as you create it if you are using back and forth strokes, or stroking into the edge. Also, you may have the angle too high. Have you felt or tested the edge to see if it seems like it is sharp? Try going to a finer stone like 120 grit and see if it gets sharper.
 
I would love to use belt grinder and usually i do it like that but problem is that i have only 4x36 belt grinder and that blade is curved. If i want to sharp that narrow part of blade it will grind even to that wide part of blade but angle will be wrong. I could use just side of belt but 4x36 belt sander has corners which won’t let me do that. Maybe i will try to use my file bevel jig and then stones.
 
i would go with 30 degrees, its much easier. after you learn to feel the burr, maybe try 20 degrees. thats a lot of metal to remove with a narrow stone.
 
Gary W. Graley said:
Angle the blade towards a light so you can follow the bevel that you made so far with your sharpener and see if the bevel is uninterrupted or if it’s faceted which would indicate that it doesn’t go all the way to the edge
Also looking down on the edge with a strong light and look to see if you see anything along the edge

good luck with your work
G2
Click to expand...

OP, have you tried the above yet?? This is imo the easiest way to tell if you’re hitting the apex of your blade. Very helpful to visualize what’s going on...
 
Ok guys i finally finished sharpening! Gary W was right, edge was too tick. Also i found out that Lansky sharpener is not good choice for recurved blade. Some kind of honing rod or something round would be much better. Anyway thanks for all advices.
 
Nice glad to hear that you “stuck” with it and got her sharpened up
G2
 
On a larger knife I have reprofiled with the standard Lansky stones, 4 hours was not enough time!

I've reprofiled several big blades that way in the past.

It is likely simply that you are not hitting the apex yet. Especially if trying to set the initial edge bevel.

For future reference, sharpen after your tempering is done!!

Will sharpen easier, and be less prone to micro chipping.

When I am using the lansky to reprofile, I use a different motion until I get close to apex.

Back and forth. Then once I get closer, only one direction towards the edge and towards the tip.

One of the reasons I don't use my lansky as much any more is it is more time/labor intensive.

Of course I've never invested in dismond stones for the Lansky, just my dismond freehand stones.

I also have a 2x72 grinder, and a 1x30 grinder.. so it is harder to be patient any more!!
 
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