Wednesday, December 7, 2011

Knife Sharpening - WARNING

We all should know about HEAT and the way it can AFFECT metal.  Lets just "cut to the chase"!  Lets not even differentiate between heat and hot.  Heat MIGHT ruin a knife blade but HOT will ruin a knife blade.  Remember, I'm trying to keep it simple.  I don't think you can generate  enough heat or hot to affect your knife blade when hand honing it.  But as soon as you put power to it watch out. 
Pressing the thin cutting edge of your carving knife against a moving wheel will generate heat - if you hold the blade against the moving wheel long enough, it will generate HOT.  There is a warning that occurs when your blade is too HOT.  Of course, it too friggin late when this warning appears.  When the blade is too HOT it turns color.  The color can be blue, black, orange, red; but any color other than the original blade color is probably too late.  You've probably messed up the blade.
Most of us have broken the very tip of a carving knife off.  I mean the 1/16th " tip.  Or may if we're a bit too aggressive 1/8th ", or worse.  When this happens, we know that all is not lost.  We can reshape the blade back to a point. 
Reshaping the knife blade back to a point is where we can get into real trouble.  We have two choices hand or power.  I prefer hand shaping the point, with a diamond "stone".  However, recently while carving at the Senior Center where we have a power sharpening system I used it.  This system has two wheels with emery/crocus wrapped wheels (one fine and one medium grit).  I used the finest wheel, and reshaped the back of the knife blade so that it came back to a point.  I got cold wet sponge to keep the blade cool, and started.  Touch the blade to the moving wheel for less than a second, then cool it in the wet sponge.  Repeat this sequence until the blade tip is returned to a point.  TAKE YOUR TIME.  After I reshaped the blade to the necessary point it occurred to me that there is a teachable moment here.
Where is the knife blade the thinnest?  AT THE TIP!  Where is the knife blade the most susceptible to getting HOT when shaping/sharpening? AT THE TIP!
There's less than one second between BURNING the blade tip and not burning it.  Error on the side of time.  Take your time when sharpening and/or reshaping the knife blade.  Or as Ol' Thomp said, "Touch the tip, dip the tip; touch the tip, dip the tip".  Dipping in this instance means dipping the blade into water to keep it cool.


Bruutmans said...

Hi there Tom,

Thanks for the tips again!
Verry usefull. I think a lot of people know it,but it can never harm to say it again and the new ones learn something.
I`ve had the experience myself,it turned real ice blueish on the tip and it was al over. Start again my friend!lol.

Best regards Dries

Mike said...

Tomz knife messager great sharpener impossible to burn a blade up. It runs at about 30 RPM 7' its eazy to clone if your the handy type

Desi said...

I use a dremel with a grinding stone atachment to reprofile knives, applying only light pressure to complete a single quick pass over the blade, then cooling the whole thing with a spray of water from a pressurised sprayer.

Tom H said...

Mike, I too have and use one of Tom's knife "messagers", and like it.

Desi, I have used the Dremel with a cutting disk, but not a stone. Next chance I get I'll have to give it a try.