Mount EMT on the shaft hole by either compressing or expanding the diameter. (Squeeze it evenly into a screwdriver if it is too large or pry the edges of the aperture break once until EMT fits the hole slightly close.) Insert EMT into the pulley or collar hole. Rotate the opening you cut until it is where the clavicle should be. Normally there will be a set of screws and the key will be aligned with it.
Note the yellow line. Put the assembly in a wing so that one of the jaws covers the yellow line. The other jaw will cover the same area at the opposite end of the EMT. The record or collar will be able to turn a little on EMT. Lock it in place by easily driving the wedge end of a straight screwdriver between the pulley or the collar and the cradle where the green arrow appears in the graphic.
See the second graphic . The exact cut you made in EMT is located just above the yellow line. Use lightly downward pressure on the file to keep the insert straight and parallel. Apply most of the pressure during filing to or against the point of the large green arrow. Release the pulley or collar of the EMT by removing the screwdriver wedge, shifting the collar or pulley one piece to make the key cut the desired width and lock in place with the end of the wedge on the screwdriver. Continue archiving.
It can be a slow patient process, but the EMT archive guide lets you produce a good keychain. The depth of the keyway must be level at both ends and through the center. You may need to make some final adjustments to the file when trying to fit on the pulley or collar over the key and on the shaft.