Jaggy Taggy wrote:
Every now and then I have to mill air channels into 1/4 acrylic
sheets,
which afterwards are being glued up for air manifolds.
The pieces are strips of 2" X 18" and I need to make 17" long slots
1/4"
wide all the way thru as well as 3/4 depressions about .050" deep.

Once I did this on a router but it is too fast and gums up the
material.
Now I try a milling machine, but I am still wondering about the right
speed/feed as well of course about a clever way to hold down such
shapes on
the table.

I would appreciate help in this matter

Uwe

Its ALL about the tooling with Acrylic and many other plastics.
Have a look around at this site: http://www.antaresinc.net/

There is a link that shows industrial tooling, and then sharpened
tools. You will have excellent success with their Parallel single flute
"D" blank cutters.

They have some really good information in their "fact Sheets" link.

Others sell "D" blank tooling, but that is the only quick site I could
connect you with.

(crown cutters is another)

Chris L