The next step with our knife is to shape the cutting edges. While the width of the faced is a matter of personal choice, we prefer to work to a formula of 4 times the thickness of the blade. Thus, if you are working on 1/8 inch steel, the facet would be about ½ inch. To make the facet any less would give a strong edge, but it would be hard to cut all but the softest objects. To produce a wider facet would give an apparently sharper blade, but there would be greater chances of chipping the edge. (We stressed the ‘apparently’ above because the edge wouldn’t necessarily be sharper, it would just cut easier – and chip easier).
Draw a line parallel to the eventual cutting edge, and 4 times the thickness of the blade, in from the edge. Mark the other side at the same time.
Holding
You should have already drilled the holes for the rivets. You can use the holes to screw the blade down onto a piece of scrap wood. The wood should support the full length of the blade, and will give you something to grip in the vise.
Shaping
With one of your coarse files, start filing away the excess metal. Cut down to the line, and almost to the midpoint of the thickness. You can usually judge this by eye. While you could mark the midpoint, this shouldn’t be necessary.
Keep checking for pinning, and remove them if they occur. As we said before, scratches will only have to be polished out at a later date, so time lost now will be saved later.
When you are almost down to the line, turn the blank over and repeat the process on the other side. Note that you have not yet moved to finer files, and you do not want to produce a sharp edge at this stage! If you can get down to about four thicknesses of paper, that will be sufficient. It is too easy to cut yourself when working on the unfinished blade.
Check the filing to see that the facet is parallel, that there are no waves or curves along the cutting edge. Hold the blade at arm’s length and look along the blade. Any inconsistencies in line will be apparent. You should file these spots out. If this filing produces sharp spots on the edge, rund the file along the length of the blade several times to prevent accidents at a later date.
Smoothing
When you are satisfied with your rough filing, start working down through the file grades. With each of the finer files, you should remove the scratch marks left by the previous file. If you do this carefully and finish off by draw filing, you will produce quite a fine finish – just off the file. Chalk dust on the file for the final draw filing will give you a very good ‘rough’ finish. At this point your knife should look like the one below.
