KentM wrote:abroxis wrote:Has anyone ever tried this technique.
Reading through a book on impressioning tips someone mentioned an idea to make the marks easier to see.
ANNEALING.... They suggested heating the brass key cherry red with a small hand torch. Supposedly this will soften the brass enough when it cools that marks will be much easier to see.
It takes some skill to know how to do correctly and it may make the key liable to break but might make it easier.
Sorry to open a not too old thread, have any one tried aluminum keys for impressioning? I think these would have stronger and more clearer marks for impressioning.
Second question, can we get automotive keys made up of aluminum, I know they are more ductile than brass and can break easily, but I think, these could be good contender for impressioning?
Kent
None of the books on impressioning that I have recommend aluminium keys. I personally haven't tried them buy I do know that aluminium is a real pain in the butt to file and clogs your file. I don't know exactly what type alloy of aluminium keys are made from or what type of brass is used to make keys so I just used the averages available on
http://www.matweb.com.
For the purpose of impressioning we want a measure of indentation resistance such as
Rockwell. For both brass and aluminium the B scale (HRB) is used. From MatWeb I get the following HRB values:
Aluminium Alloy:
Hardness, Rockwell B 45.0 - 96.0 (Average value: 68.3)
Brass:
Hardness, Rockwell B 25.0 - 133 (Average value: 69.8)
So depending on exactly what sort of aluminium alloy or type of brass the hardness (indentation resistance) may be almost identical.
The rotational force applied to a key when impressioning is a shearing force so we want to know the
shear strength. Matweb also gives us the shear strength.
Aluminum Alloy:
Shear Strength 0.138 - 420 MPa (Metric) 20.0 - 60900 psi (English) Average value: 101 MPa
Brass:
Shear Strength 205 - 415 MPa (Metric) 29700 - 60200 psi (English) Average value: 273 MPa
So, in general, brass has a much higher shear strength than aluminium and a brass key -- on the basis of the average -- is much less likely to snap. If we knew exactly what sort of brass and alumium were used in key blank manufacture we could get the exact mechanical properties but failing that we can only use averages and the averages seem to match real-world experience of the shear strength of aluminium versus brass key blanks, i.e. aluminium keys snap quite easily.
I suspect that for these reasons (file clogging, roughly same hardness as brass and lower shear strength) aluminium keys aren't recommended for impressioning.
The master impressioners, including the current world record holder (Jos Weyers see
http://www.youtube.com/watch?v=BLlIg2pxGEM http://www.youtube.com/watch?v=s8aQSxXoLFk), recommend brass key blanks. The tip for making marks visible (without any other material such as soot, paint market, UV marker) is to to use a fine cut file (at least #4 Swiss cut) to produce a smooth and homogeneous surface before starting the impressioning
and after each round. You want the key surface to be smooth and even throughout, before it goes back in the cylinder, so any marks are conspicuous. Another master impressioner, Oliver Diederichsen, makes the good point that some keys are only available in nickel-silver and for this reason you need to be able to impression with these also.