Reading an advertisement for machine tools touting hand-scraping as the
last word in smoothing machine tool bearing surfaces after grinding, the
thought to try the technique on the pole surfaces to which the magnets will
be glued occurred.
Reading an advertisement for machine tools touting hand-scraping as the
last word in smoothing machine tool bearing surfaces after grinding, the
thought to try the technique on the pole surfaces to which the magnets will
be glued occurred.
Shown between the poles is one of the first ribbons cut. The material is household aluminum foil. There are many flaws in the ribbon shown, and it would not be used in a working driver.
There is an odd effect that has occurred with the polishing/flattening
of the pole faces, the steel now has a distinct blue tinge. I've
previously read the phrase 'blue steel', but always thought that it
referred to chemically blued steel, as in a gun finish. The photo at left
only hints at this effect (a monitor or TV can never show the full range
of human color vision). The 'silver' of the aluminum foil provides a
distinct contrast to the 'blue steel'.
The aluminum crossbars which support the pole pieces were mounted on springs
so that the front-to-back position could be critically adjusted for top-to-bottom
linearity. After that adjustment was made, using a stretched 34 gauge wire
as the reference for straightness, the crossbars were epoxied in place for
permanence.
At the extreme right in the photo an epoxy putty filled section of a bolt hole can be seen. Large cavities at the rear of the crossbar interface with the red oak framework (shown covered with borosilicate damping compound) were also filled with the putty.
The carriage bolts connecting the poles to the aluminum crossbars
are non-magnetic stainless steel.
The red oak quarter rounds which create the throat of the ribbon gap
between the poles are no longer completely rounded, but have flatted
sections at the air gap interface and on the outside edges to match the
height of the ceramic magnets which will glued to the pole pieces.
Part 5b - The Cutting Bench & Micrometer Straight Edge.
Part 5c - Plan 'B' Ribbon Cutter.
Acoustic Line Source Research - Table of Contents.
