The standard procedure (without jigs and special grinders) is to tape the ends of a chain saw file and a piece of round rod (the same size) together at both ends. This will make serrations spaced the size of the file, so a 1/8 or 3/16 file works well. Make a starter groove with the file, at an appropriate angle to make the serrations form in the edge ( somewhere between 20 and 45 degrees). Don't make it fully as deep as you want, just about 75%. Place the round rod in the groove you just made and file the next groove. Repeat for all the serrations desired.This will make all the serrations spaced exactly the same (which would be hard to do by eye) When all are cut in, take the next size larger chain saw file and file the grooves until the points almost meet.The size of the second file will determine how shallow or deep the grooves are. Once the rod/file grooves are made, you could use a Dremel tool or flexshaft with a cylinder burr or a cylinder stone to complete the job, but it takes a steady hand.After HT, finish the serrations with a ceramic rod to make the points touch and sharpen the hollow edge.
Now, for those of you who want to do it faster, I'll tell you a way to do that ( but faster is usually not better) .
Get a HF electric chain saw sharpener. They cost less than $30. They look like a tiny cut-off grinder/saw (chop saw) made from plastic.Round the edge of the stone wheel to the radius desired, basically a near half-round. (The best thing to do is throw away the stone that comes on the sharpener and replace it with a good quality 1/4" wide stone. They are cheap on ebay.) Set the grinder to 90 degrees.
Now, take a 12" piece of steel and flat grind it to a basic blade edge (just for setup and practice, no need to make it look like a knife).Coat the "blade" with Dychem and, as accurately as possible, mark the edge every 3/16 inch. Make a wooden rest/jig to set the blade on that will sit in the right place for the stone to contact the blade in the right spot to make a serration. Carefully grind the first serration. Move the blade and grind the next....etc. (You could make a jig fixture, sort of like an Incra jig for dovetails, to space the serrations, but that would be overkill.) It may take some experimentation with the angle that the blade sits in the rest/jig to get it all setup right, but when all is figured out this will quickly cut a row of serrations. Be Aware, you can easily over-grind a serration too deep. It is best to grind them to just shy of touching, clean them up by hand with a chain saw file, and finish with a ceramic rod after HT.
This is a home brew version of the way it is done in the factories.
Stacy
