Going deeper in technical information provided by Technics in their patent from 1979 i’m shocked how complicated in manufacturing can be one tiny part of the phono cartridge called the cantilever!
Boron is known to have a hardness next to that of diamond and a very large resistance to abrasion, so that it is useful e.g. for cutting tools, sliding components and bearings. Further, since it has a low density and a large elastic modulus, the elastic ratio is largest among all the presently known materials. This means that the sound wave propagation velocity in boron material is highest among the presently known materials, so that boron is particularly useful for a cantilever for supporting a pickup. This invention (patented in 1979 by Technics) relates to a boron cantilever and a method making the same, particularly to a boron pipe cantilever for supporting a pickup stylus for converting shape signals recorded on a recording medium to electric signals, and a method of producing such cantilevers with a high production yield. According to this invention, a boron cantilever, particularly a boron pipe cantilever having a high mechanical strength and an excellent elastic ratio, ε/ρ, can be obtained, where E is elastic modulus and ρ is density.
Some new facts (at least for me):
Technics was way ahead of its time when they invented amorphous Boron Pipe cantilever back in the 70’s. Generally, a pure amorphous boron layer is best in view of mechanical properties such as tensile strength. It has been found according to this invention that a stronger boron cantilever can be obtained by a boron multilayer pipe, in which each layer is in a limited thickness. The thickness of the wall of the pipe cantilever is determined by required weight of the cantilever, required acoustic properties, etc. It has been found according to this invention that a boron cantilever pipe having a certain wall thickness and composed of plural boron layers is stronger than a boron cantilever having the same wall thickness composed of a single boron layer.
Among various known methods for forming a boron layer, the CVD is considered to produce the best quality boron layer. However, commercially available boron fibers are sometimes mechanically weak due to porosities, inner strains, micro-cracks, etc. Further, when a metal substrate having an amorphous boron layer thereon is removed by, for example, etching the metal substrate, the amorphous layer sometimes gets broken. This is considered to be because of the inner strains in the boron layer.
A CVD-deposited boron multilayer on a metal substrate according to the finding of this invention is strong even after the removal of the metal substrate, and is good in appearance also. The thus prepared boron cantilever is excellent as a cantilever. In this case, the thickness of each amorphous boron layer in the multi-layer structure is preferably between 3 and 15 microns.
P.S.
Some of my Technics top of the line cartridges
here.
But look at
Technics Boron Pipe cantilever in comparison to the Grace
LEVEL II Boron Pipe cantilever. These are the most expensive cantilevers made for phono cartridges in the 80’s.
This type of cantilever (Grace) is not available for modern cartridge manufacturers, instead they are using inferior Boron Rod now (and mostly for expensive MC, not MM).