Milling Circuit Boards
          I have been milling circuit boards for the last three years!  I mill all my prototypes. If the design works out, I sell the milled boards for awhile and then I send the boards out and have them etched at a PC house.

         So for the last three years I have been helping people learn how to mill circuit boards.  I designed a machine called "The Brute" that can be used to mill and drill circuit boards. I sell the plans for making "The Brute" here on this website. I don't sell a completed machine.

Here is "The Brute" milling a circuit board
Note: the masking tape wall that keeps the dust from
dropping onto the leadscrews of the machine.


           I hang out on several Internet conferences. Whenever the subject pops up about milling circuit boards I try to help.  There seems to be alot of bad information going around!

         To start with!  Taig and Sherline mills are too slow. If you own a Taig or Sherline you will need to buy or make a holder for a Dremel or other high speed motor tool. You need 15,000 rpms or higher. The milling bit needs to be carbide! HSS bits will only work for a short amount of time. The glass epoxy circuit boards eat steel bits very quicky. Carbide is a must!

          The board is mounted to a piece of PVC or PlexiGlass that is bolted to the bed of the mill. The board is held around the edges by bolts that are tapped into the PVC or PlexiGlass. The heads of the bolts pull the board flat. Don't use double sticky tape! It can let the board come loose and it won't hold warped boards flat!

          The bits are called Mechanical Etching Bits. You can buy them from Think & Tinker. They are 60 degree solid carbide. The tip of the bit forms a triangle. This allows you to mill boards that are not perfectly flat.  Forget about adding a depth foot, it will hangup on the milled edges of the traces and the dust from the milled board. The expensive machines use a vacuum system to remove the dust.
 


Here is a board right after it has been milled The board
is 4" X 6" and has 800 inches of milled isolation. The
board took over two hours milling at 6" per minute with
the Dremel spinning at 16,000 rpms.
 


All my artwork is done using TurboCad.  I use a .025" grid to lay out my circuit boards. After I draw my artwork I trace it in a new layer. I delete the drawing and save the trace. When the trace gets converted, the GCode mills in the same order I traced the artwork. 


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