Wednesday, March 2, 2011

CNC Router Part 3: Building the Base

First step is to cut and drill the front and back of the base from MDF.

  1. From a 2' by 4' sheet of MDF cut off 24 1/2" piece.
  2. Adjust the table saw to exactly cut a 4 1/2" width. Cut and check with scrap wood. Now cut two pieces 4-1/2" by 24-1/2".
  3. Take one piece and set it face up. This surface will be designate as the rear of the back base plate. Using the drawing below, mark the vertical position of each hole. Start by finding the vertical center and mark that. Remember the piece is 24-1/2" wide so the center should be 12-1/4" from one end. Now position all the holes from the center line and mark each hole position from the bottom edge. Also mark the ends of the piece, 24", and the 45 degree cuts. Note: I used a center finding ruler, Utrecht 36 inch, Item No: 56746.
  4. Dimple each hole position lightly with a small center punch.
  5. Now, sandwich the two pieces together and place on the drill press table with the marked side face up and the bottom edge against the fence. Using a center bit or a center finder adjust the fence for hole number one. Making sure the ends are squared up then clamp the pieces to the table. Drill hole number 1 with a 1/8 inch bit through both pieces and insert a spare 1/8 bit in the hole as a pin. Notes: (1) Drill slowly or else the bit may bind or overheat. (2) Use a good quality bit for drilling and cheap bits for pinning.
  6. Drill hole 2 as you did hole one.and leave it pinned.
  7. Now reposition fence for hole numbers 3 and 4. Hole 3 which is on the center line will be drilled through both pieces with a 5/8" Forstner bit.
  8. Place a 3/4" Forstner bit and set to a drill depth 1/4" above the table surface. Re-position the pieces for hole number 4 and drill both pieces. This hole will not be drilled through the front pieces because of the stop.
  9. Re-position fence for hole 5 and drill with the Forstner bit.
  10. Leaving the pieces pinned, use the cut off saw to cut the pieces to length and cut 45 degree ends.
  11. The pieces are now ready for the next step.Remove the pins. Because of the symmetry, mark each piece: front of front, rear of front, etc.

    The next step is to cut the 1/8" circular groove for the PVC pipe into the back of front and front of back plate.
    1. You will need a Dremel rotary tool, a Dremel 678-01 circular cutter and 1/4" straight router bit (654).
    2. Following the Dremel instructions set the cut depth to 1/8" and outer diameter to 1.9". Using a piece of scrap MDF cut a circular groove and check the pipe fit, 1-1/2" schedule 40 PVC.
    3. Now cut the grooves in the rear of the front plate and front of the back plate, 4 places total. See picture.
    Next is to drill the motor mount holes. The following pictures show the centering of the motor template over the bearing hole. First, the 1/2" by 5/8" sleeve bearing was inserted into the hole and second, a 1/2" drill with a quarter inch shank was inserted into the bearing. This shank was then used to position the template. After aligning with a square, spring clamps were used to hold the template in place and the 3/16' holes were drilled. These holes were later drill out from the rear to 5/16" and a depth of 1/2". The later step was for the 10-32 EZ Lock threaded inserts.

      Next step, enlarge the four 1/8" holes to 23/64". Center the hole on the drill press table and clamp the piece. First, drill out the hole with a bullet nosed 5/16" bit, then enlarge to 23/64" with a regular drill. I found that the bullet nose drills do not chatter. These holes are now the right size for the 1/4" cap nuts.

      Next step, mount the 3/4" aluminum angle. First, cut two pieces of angle to 18". I did this on a cutoff saw with an aluminum cutting blade.

      BOM: CNC Router Base
      1. 1          MDF 3/4", 2ft by 4ft
      2. 6ft        1 1/2" schedule 40 PVC pipe
      3. 4ft        3/4" by 3/4 by 1/8" Aluminum angle
      4. 8ft        3/4" sq aluminum tube
      5. 2          1/2" bronze bearings flanged, MC 1677K9
      6. 2          1/2" thrust bearings, MC 6655K17
      7. 2          1/2" collar aluminum, MC6157K14
      8. 4          2" #10 unthreaded standoffs, MC92511A032
      9. 4          3", 10-32 PH PHIL screw, MC90272A842
      10. 1          Lovejoy coupling 1/2" by 1/4", Amazon
      11. 4          1/4-20 threaded rod 3ft
      12. 8          1/4-20 cap nut, MC90835A310
      13. 3ft         Acme precision threaded rod, MC99030A005
      14. 2           3/4" 1045 precision steel rod ground/polished, Speedy Metals
      15. 2           1"OD Aluminum round tubing, 3ft, Speedy Metals
      MC =


      1. Do you have a rough sketch to show where you are going with the overall structure? I like how you add sources for the stuff you are using. It makes it easy to look up what you are talking about.

      2. The machine looks like the Probotix Fireball, but not so pretty since made of MDF.

        I have the design worked out, but I write a detailed build procedure before I start each part.