Back when I made that plane,I was just using slim triangular files with the ends ground to made an engraving chisel. Cut off the tang,and wrap the file in string to keep from wearing your hand out over the naked file teeth. After hours,the teeth can begin to be uncomfortable,plus the angular corners of the file.
I used a small chasing hammer,which I also made,to drive the engraving chisel along. Every hammer tap moves the chisel a very small amount,allowing you go go around curves smoothly without leaving a series of little straight lines connected together,if you see what I mean.
I can get by with just drawing the basic "C" and "S" curves to fill the spaces properly. I go freehand from there,but I warn you,that takes lots of practice. What you want to do is fill the spaces evenly,with no places that are too sparse,OR too busy. You need to de able to draw well,to make the C and S curves,and the other details look proper. If you can't draw,you can't engrave.
Later on,I made proper engraving chisels(known in catalogs as die sinker's chisels) from HSS,which I bought as ANNEALED 3/8" squares from Latrobe,and hammered at only a blood red heat into the tapered chisels I wanted. The chisels were not further heat treated,and though this is not the correct way to harden HSS by any means,it made the chisels very hard,but also MUCH tougher than the normally rather brittle(for this application) HSS. If you want to buy decent steel,buy some 1/8" square cobalt HSS,and mount them into straight 1/2" dia. handles. One of the greatest gun engravers taught me that,Lynton McKenzie. He is now dead,but did incredible work,and was a good friend.
