How should I properly round off a 90 degree blade shoulder?

[Frederic Buner]

How should I round off a 90 degree blade shoulder with sharp corners to reduce bending stress.

Which method should be used, the first, second or third?

 

I have tried the first one. Just removed material with a round file of 2mm diameter until it reached the tip of the corner. Now I'm worried if it was an improvement at all or if I even made it worse.

 

 

 

 

 

Edited March 13 by Frederic Buner

[Alan Longmire]

None of the above.   There needs to be a tiny radius in the corner, similar to your #1, but not recessed into the corner.  It doesn't have to be huge, just enought to be not a sharp corner.  A regular file is fine, they tend not to leave a truly sharp corner unless you've modified it to do so.  

 

It's more for preventing cracks during heat treatment, but if you want to be obsessive about it be sure any sharp transitions have a tiny radius and are polished.  

[Joshua States]

IMNSHO, the obsessive nature of relieving the tang to blade shoulders rounded is overblown. As Alan pointed out, none of the tools we use (grinders, files, scrapers, etc) actually leave a 90 degree corner. There is always a small radius in there.

[Gerhard Gerber]

Easiest for me is to drill in that corner then work down the tang and ricasso/blade till everything is level leaving only the radius in the corner.

Even a tiny drill bit will give you more than enough relief.