An experimental impressionig aid .....
In a video by Mikey1 he used a cylinder core for 'something' and I assumed that he had turned a cylinder core into a filing jig, for pre-marking the blank blade. Since the cylinder was made of brass I wondered how many keys could be marked without the slots in the filing jig getting filed away. The other problem is that some blanks have a width that is already pretty close to a zero cut and marking the pin positions with a file could wipe out a zero cut completely, rendering the blank useless.So one question was how to mark the filing positions on a blank, without reducing it's width. I chose a chisel punch for a first attempt.
The cylinder core is basically unmodified, I have only cleaned up the ends a little. The blank key is fitted into the core and secured in place with a rubber band. The tool is then placed on the core and blank assembly, with the chisel punch in one of the core holes. Gently strike the chisel punch and it marks the blade, then do the other four markings in the same way. This should be done before preparing the blank edge for filing. The idea of the slot in the tool is to keep the chisel at exactly 90 degrees to the blank blade, as it slides backwards and forwards on the bow.
Metal displaced by a punch has to go somewhere, in this case a little appears on either side of the indentation and a little spreads sideways. Bearing in mind that the next operation is the preparation of the blade edge for impressioning, both of these will disappear, especially if blade thinning is employed to speed up impressioning.
The indentations are too narrow to affect a pins, but do provide an excellent guide for those first few strokes of the file. Now it may well be, a little experience will quickly replace the use of the tool. It may also be that you may have a better idea ?. My next problem is finding a way to see the marks during impressioning.