Frame’s metal not the most important thing…

It is also important to note that the machine frame’s metal is not
the only factor you have to consider. The coils, springs, armature
bar, capacitor, and contacts in that order are also important.
It is almost a balancing act of importance. A change in one area
of the machine will require compensation or a change in all others
typically. These are the things that will require experimentation.
There are general rules of thumb, but you really have to
want to learn how it all works. If you do not have the desire to
gain the ability to tune and tear apart your machines on the fly,
you will more than likely just be another mediocre tattooist.