Drew :
A machine is all I need to tell me I'll never make a good blade out of zinc
What machines can do very well is give you precise estimates of very specific material properties. You could do this without the machines of course, but it would just take much, much more work. They are great for this. My starting interest in the CPM steels was initiated by reading the specification sheets from Crucible.
What is most important though is that you have to realize that the answers are *extremely* specific. This is where the real problems start. You have to know exactly how the experiement is being done to determine what the results mean. Most materials testing done is extremely simplified for exactly this reason.
if you want to answer simple questions like "what's its original cutting performance in medium X" or "how long does it hold an edge cutting medium X
Those are not simple questions and they will not be well handled by a machine.
What a machine could do well is answer the following :
"Determine the the force required to push blade XXX through card stock of grade YYY as a function of length of card stock pushed through. Blade XXX is to be held in a fixed position in the vertical and horizontal and at a set angle to the stock. No motion is allowed except straight through the card stock. The experiment is terminated when the force exceeds ZZZ."
Now just think about this and compare it to actual utility work with a blade.
Regarding that test, if the blades used are of equal geometry you will not be measuring real life edge retention, too many very necessary factors are being left out. What you are determining mainly is wear resistance and while this is very useful info it has to be realized that is all you are obtaining.
specialized machines using identical blades give the most scientific answers.
No they do not. The quality of science is independent of the equipment used. It has nothing to do with it all all. It is how you use the equipment you have. I have much better equipment than Newton had, my work is not much more scientific.
As a simple example of the independence of equipment, one of the first things I do when teaching a class how to do an experiment correctly is have them estimate the acceleration due to gravity with just a piece of lead. No watches or devices for measuring time are even used. It is easily possible with a little care to get an estimate that within the tolerances of the experiement (which are also estimated) matches the known value. The bigger the class size the more precise the result will be it does not get any more scientific however.
-Cliff
[This message has been edited by Cliff Stamp (edited 02 September 1999).]