>>Expanding on those, any heatsink you buy will not
>> be flat enough without machining, ideally with a large diameter
>> 'fly' cutter. You are also looking for a good surface finish with
>> machining ridges barely detectable with a fingernail. As well as
>> flat (50um or .001" over the module area) clean is important.<
> Not sure that I would agree about a fly cutter. Better than nothing, but I
> would prefer
> a horizontal milling cutter. Alternatively, a face-and-end milling cutter.
> A large slot drill
> might give a good enough finish.
> Another good way would be to use a shaping machine.
The choice probably varies with the machinery available. Up to 6"
wide I get things skimmed on a single pass and they give me a low
roughness finish. With end cutters or slot drills the finish is
usually excellent but there can be a tendency for tiny
steps/ridges between passes - I've learnt to specify that any
mounting area must be cut in a single pass.
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