Wheel Mounting Plate
A long time ago, in a previous life, I studied CNC programming and briefly worked as a CNC machinist. You can make some pretty cool parts with a CNC machine. I was extremely pleased when my friend Jim recently decided to buy a CNC machine for his shop. He picked up a very nice CAM software program also, making it very easy to get fancy. Monday night together we made the trickiest piece in the whole project, the mounting plate for the steering wheel.
Rather than doing elaborate work on the dash wood, I decided to make a plate, then bolt it onto the dash. This way, if something went wrong, I just lose a $3 piece of aluminum, instead of a $30 piece of hardwood. The plate could just as easily been made square, with rounded corners. But hey, we have a CNC machine to play with. I decided to add some bevel features and an oval profile.
The plate is made from ¼” aluminum stock. The center hole is a slip fit for the original plastic piece that went onto the housing. The wheel gear assembly has 4 screws and some other features that needed to be 1/8” from the front surface. After the main hole, we machined a pocket in the back for the wheel gear assembly. The mounting holes for the gear assembly and the dash mounting holes were drilled next. No CNC program necessary for these holes. The machine has a pretty good coordinate system that allowed me to dial in the hole locations manually within less than a thousands of an inch. The four gear assembly holes would be used to help fixture the part for the next step, the oval profile and blank cut-out.
We needed to make a fixture to hold the part. In one of these pictures, you can see a screen shot of the tool profile as generated by the CAM software. This program was used to cut away the surface of fixture wood, leaving a mirror image feature of the pocket in the back of the aluminum. This feature was a tight press fit into the part. The press fit, 4 long wood screws, and some C clamps held it in place for the profiling cuts.
There are 4 steps, 1/32” deep, and 1/8” wide around the perimeter. It took about 25 minutes to run this program. The white knuckle part of the process was the very last pass, where you cut through the last of the material, the stuff held down by the C clamps, putting all the force on the smaller screws in the center. This is typically where things can rip loose and really mess up your part. About 5 seconds from the end, the shop air compressor kicked on, making a loud sound. That was really bad timing, for my nerves anyway, the part turned out fine.
Next comes cutting a hole in the wood for the wheel gear assembly to pass through, mounting the plate to the dash, then wiring it up, then the artwork, then, then, then.