What did I do and how best do I fix it?

[DunkEm]

I'm a newbie at this knife making thing. I read somewhere that I would do well to try and sand the surface of my blade flat. So I tried. Using my Sears 2x42 grinder. I ended up with an ultra dark ???? covering on the steel that doesn't come off readily.



At this point, I've swapped out for a new belt, and taken a few passes at the grinder which seems to be working, but I'm hesitant. Is this the direction I need to go or should I try something entirely different?

And if you know why it happened (my guess is my belt was too dull) please enlighten me so it doesn't happen again.

And if you know what the dark ??? is, I'd love to know.

 

[Stacy E. Apelt - Bladesmith]

The shiny places are where it is flat. The dark places are where it still is lower than the flat surface. Continue to flat grind the blade down until it is all smooth.
Good quality metal working belts at a coarse enough grit take care of tis pretty fast. I use a grinding magnet to hold the blade while flattening the sides. Flip from side to side often. Don't just grind all on one side.


Blade shape looks good, BTW.

 

[DunkEm]

Thanks.

 

[DunkEm]

The shiny places are where it is flat. The dark places are where it still is lower than the flat surface. Continue to flat grind the blade down until it is all smooth.
Good quality metal working belts at a coarse enough grit take care of tis pretty fast. I use a grinding magnet to hold the blade while flattening the sides. Flip from side to side often. Don't just grind all on one side.


Blade shape looks good, BTW.

Follow up question...

It's that way on both sides of the blade. Is that just a sign that the steel is thicker on the edges than the center? I was thinking that one side should at least be basically flat and beginning to get worried that something is wrong with my grinder platen (which has a piece of glass on it).

 

[Stacy E. Apelt - Bladesmith]

What you have discovered is that it is nearly impossible to hold a flat surface on a grinding belt and not take slightly more off on the edges than the center. A shapr lower grit belt and a firm grinding magnet makes it a bit easier. The big guys use a surface grinder to get it dead flat. Many folks who only do stock removal opt for buying PG steel ( precision ground). It has flat and parallel sides and all scale is removed. The cost is only a little more.


Also, as the steel goes through the rollers in the mill, there will be slightly thicker places and slightly thinner places. Once the scale is removed, these don't slow much to the eye, but they are there. Because they are roller through two rollers, a thick spot will be thick on both sides.