Often when you find saws, the nib on the leading edge is missing, or gone completely. Also if you shorten one, a new nib should be added back. I’ll go over my process for creating them, and a few tips I find helpful to elevate the final look. I will not get into their function. Lots of speculation out there and I don’t think anyone has found a definitive answer.
As a rule, nibs are found on straight back saws only. Picture the very popular Disston No. 7. One has to wonder if Henry Disston, when designing the first skewback, Choice 80 used the opportunity to simplify the process by leaving it off? Regardless, I’ve found nibs on at least one (warranted superior) skewback design. I suspect, however, it was added later by a saw smith with a sense of flare.
The good new if you’re already filing saws you most likely have the tools needed. I find used files work fine with the smaller files working best. I also use a set of jewels files however I’m told historically they were made with just the triangular saw files.
The next thing you’ll need is a template. The simplest thing is to use a saw with good nib. Lay it on top, use an “ultra fine sharpie” or metal awe to trace the slope and nib.
Once done, I start the process with a triangular file to shape the bottom right angles of the nib. Then work back to the shoulder. After that, it’s just a matter of fine tuning till your happy. Keep in mind nibs most often were filed by hand and do vary from saw to saw and even within models. So don’t over think it and just make something esthetically pleasing to the size of the saw.
Look sharp: Watch that the area your nib touches the baseline DOESN’T dip below it. The one edge of the triangular files has a tendency to dig as you shape the side of the nib. Looking at this nib you will see from the shoulder to the tip is on the same plane.
Finishing touches: Take a look at the area you just filed. The filed edge will be blunt and wider then the rest of the top edge. The original top edge, either through use or design was tapered to some degree. Using a flat bastard file; like the one used for jointing, gently file the edge to match the rest of the saw. Once done it’s nice to use a little darkening agent commonly sold for touching up bluing on gun barrels to darken down the area. Then blend with the rest of the restoration.
restoring saws one nib at a time.