I wanted a way to quickly locate some holes in small stock for a robot project. I realized that my CAD file already had everything I needed in it; all that remained was a way to transfer the measurements from the computer to the actual material I would be drilling.
Step 1: Tools and Materials
- CAD program (I use Sketchup because I'm cheap...)
- utility knife
- cutting board
- metal straight-edge
- Scratch awl
- drill and bits
- a few pages of cardstock, sized to work with your printer
Step 2: Make a 2D Projection
The example picture shows a white rectangular bar with a couple of cylindrical motors and a shaft attached to it. Holes will need to be drilled in white bar to accommodate the motors and shaft, as well as the screw holes to hold the motor face plate to the bar.
I made a 2D projection of the face of the white bar. On that projection, I carried forward the center of every hole that needs to be drilled (see the dotted lines) and marked the center with a cross-hairs. Additionally, I drew a circle around each crosshairs with the needed hole diameter and used Sketchup's dimensioning feature to note the radius for drilling.
Step 3: Print the Projection
Print the projection to card stock. Make sure you set the printed scale to be 1:1 with the model dimensions.
Step 4: Cut Out the Template
Cut out the template using a metal straight-edge and a utility knife. Don't cut all the way around; leave tabs, as shown in the second picture -- these will help later with positioning. (Like my pretty flowered cutting board? :-) It was left behind by the previous owners of my first house -- it's been great for shop use! The glass surface is perfect for using a utility knife.)
Once you've cut it out, lightly score and fold the tabs, creating positioning guides as shown in the third picture.
Place the template on the stock and tape it into place as shown in the last picture.
Step 5: Drill, Baby, Drill!
Use a scratch awl or a sharp nail to poke through each crosshairs and put a dimple in the drilling stock. (If you're drilling metal, also use a center punch to make a bigger dimple.)
Optional -- if you're drilling white plastic like I was, run some Sharpie lightly over the dimples. The hole will stand out better (see the second and third pictures).
Now, drill! I am making two identical parts, so I stacked two pieces of stock in my drilling vice (fourth picture) and then drilled my holes using the appropriate bits (twist bits for the smaller holes and Forstner bits for the big holes). The resulting parts (and a third part that shares a single hole with the first two) are shown in the last picture.