When the blade is cool enough to handle, I put it on a hardened, precision, flat piece of steel and hold it up to the light to see if there is any warpage or bow. I place the blade, with the side that I ground flat on the disk down, on that piece of steel. This side will let me know how much the blade has moved during heat-treating. Since, prior to heat-treating it was absolutely flat, the light will show any gaps.
If the blade has a bow, I use my arbor press to straighten it out. I remove the anvil that comes with the arbor press and replace it with a horseshoe-shaped piece of aluminum. The gap is about 2 ¾ inches wide and it lies on the base. This allows me to move the block of aluminum side to side so I can manipulate the steel as it requires.
By pressing the blade in the center of the gap, you produce a consistent curve throughout the blade. By shifting the aluminum plate off to one side, you can pinpoint a specific area to correct. Keep in mind that you have limited time to do this before the blade becomes too hard and brittle.
This is well worth mentioning—damascus steel has a much higher tendency to warp because the steel is placed under a tremendous amount of stress during the initial forging process. From my experience, when it comes to warping, twist-pattern damascus is one of the worst offenders. This is due to the nature of the process used to achieve a twist pattern.
After the straightening process, the blade is double tempered and then it is time to start working on it. The entire edge of the blade is refined, straightened and brought to a 400-grit finish. I profile the edge of the blade with a smooth 90-durometer, 8-inch wheel. I use a hard wheel for this process because I want the edge to be flat with minimal rolling of the corners. A softer wheel, if pressed hard enough, will roll the edge of the material.
When the edge is completely done, I flatten one side on the disk grinder. The side that I flatten is the same side I flatten prior to drilling and heat-treating. This gives me a known flat surface on the blade. It also removes any type of warp or bow to that one side.
If you do not flatten one side and there is a slight bow, when you surface grind your blade, the magnetic chuck will pull the blade flat. The result is that you will have a parallel blade but it will be bowed. So by flattening one side you will have a straight and parallel blade. If this was a plain stainless steel blade, I would surface grind the blade to a particular thickness. Since this is damascus, the surface grinding will take place later.
NEXT STEP: Download Your Free KNIFE GUIDE Issue of BLADE Magazine
BLADE’s annual Knife Guide Issue features the newest knives and sharpeners, plus knife and axe reviews, knife sheaths, kit knives and a Knife Industry Directory.Get your FREE digital PDF instant download of the annual Knife Guide. No, really! We will email it to you right now when you subscribe to the BLADE email newsletter.