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Am attempting to join multiple complex-shaped ferrite pieces, namely
TV-yoke cores. Many of these are split into two halves. In any case,
they will be re-wound with copper in a way that will direct magnetic
paths through the join gap. More that a few will be joined.
A gap-free joint is wanted, so magnetic paths are evenly distributed
through the joint and not confined to small regions where mating
surfaces contact while other regions have some air-gap.

Seems to me that ferrite is glass-like, so mating? surfaces might use
lapping techniques. Mirror-like surfaces not required. Wonder if
anyone has experience here (I don't)?
Would wet emery papers work? Aluminum oxide or silicon carbide
powders?

I used wet silicon carbide to lap pieces, wet emery works well too. I
found that even the smallest gap will indeed lower the effective mu.
TV yokes that's ok as it also increases the flux saturation point for
the assembly over a solid piece.

For RF work it can be helpful but for applications that require high mu
to live with the result. An example of a built up ferrite stack for a loop.
Laminated with no end to end gaps works very well. However end to
end gaps produce a measurable reduction in effective mu.

If you glue up the assembly use the thinnest bond possible and clamp
it. Avoid epoxy with metal fillers.

Allison
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