[ATM] How dark is dark

[Don Clement]

Hi Fabio,

 I use a  non-topping 60-degree carbide insert for threading the sharp V
thread. Most of the sharp V threading involves smaller diameter aluminum
tubing of less than six-inches diameter. My rule of thumb is 40tpi. V
threads are only as sharp a single point threading allows. Electrosharpening
or some other electrochemical finishing process make for a sharper thread
before anodizing. One could easily grind a custom HSS tool for a more acute
angle or even an asymmetrical thread form. The fragility of internal sharp V
threads is not usually an issue, since the use is for baffling and not for
mating. YMMV. Perhaps someone has done a study on thread form, pitch and
diameter vs light baffling.


Don Clement

Running Springs, California





> Are you using a 60-degree bit for the V thread or a custom angle? Any
> rule of thumb regarding ideal thread pitch versus thread diameter?
> Sharp threads are more fragile than threads with a crest; how sharp
> are your light absorbing threads?
>
> Fabio
> San Jose, CA
>
> On Sep 27, 2006, at 6:02 AM, Don Clement wrote:
>
> > I also thread the internal black anodized surfaces with a sharp "V"
> > thread for the same reason. The sharp "V" threads behave as a
> > helical stack
> > of razor edges to trap and absorb light. The sharp "V" threaded
> > internal
> > surface appears much blacker (less reflected light) than a surface
> > that is
> > smooth black anodized.
>
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