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Discussion in 'Trumpet Discussion' started by kehaulani, Feb 17, 2012.
I found that using a combination of both works very well and lasts longer.
Mwah.. ha.. ha.. ha.. ha.. ha
And welcome to ™
Ivan, what are the CNC tolerances? This same Manual talks about the enhanced tolerances used in the valve design. Could the Committee have led the way to the CNC tolerances? Maybe that is why the recommended the valve oil as the non-synthetic lubricants were adequate enough for that horn.
Also, I do as the manual says (call it the internal scientist in me) and it does seem to assist in enhancing the valve function, even when using today's synthetic oils.
Ivan here is Martin's descriptions of the 1946 valves for their Committee:
Martin valves are finished to a surface smoothness of 2 micro-inches r.m.s. which means that there is no more than 2 millionths of an inch of surface curvature. Also this geometric dimensions of each valve are within a tolerance of 2 ten-thousandths of an inch...
Not sure if this helps or not.
1940's marketing was from the era of BS. You could say just about anything back then without threat of legal challenge.
Not beyond the realms of possibility according to http://www2.mae.ufl.edu/designlab/Lab Assignments/EML2322L-Tolerances.pdf
But I'm sure Ivan will confirm that this gives limited guidance in setting a workable valve to casing clearance.
I hope nobody misunderstands; this is not a Martin bashing exercise. I have great respect for these instruments.
Martin are talking surface finish, i.e. shininess. It is the ease of repeatability of dimensions which has taken giant steps forward with the advent of CNC etc. Of course tight tolerances (not to be confused with tight fit) could be maintained back then, but it took a lot more effort (=cost).
Note that they talk about maintaining dimensions on the pistons - easily obtained with a cylindrical grinder. It is a different story with casing dimensions IN PRODUCTION RUNS.
I have some trombone slide 'oil' which seems to work very nicely. But needs the stopper on teh slide, of course. Don't want it disappearing underneath the violas
CNC is an abbreviation for Computer Numeric Control. A CNC lathe is a lathe which is controlled by computer. Simplistically speaking, one draws a shape on a computer and sends the information to the lathe which machines it. These lathes are typically more robust and tightly dimensioned than older machines, and constantly monitor (well sort of - but that's a different story) the exact position of the cutting tool. In the old days you would grind a cutting tool to shape, a "form" tool, which would, for instance cut the correct shape for a mouthpiece cup. When the form tool wore, the shape of the cup would change. On a CNC machine a single pointed tool would move around the shape required and create parts with much closer repeated measurements. It is not so much that we can machine to tighter tolerances these days (although this is true) but that we can easily repeat these tight tolerances in mass production. Remember how much trouble the early double overhead cam engines of Jaguar were? You had to adjust tappets every 1,000 miles? Now just about every car maker uses this design in the unbelievably reliable engines of today.