Careful Mill Work
Chucking the disc in the milling vise was easy since both sides were flat at this point. Since this isn’t a high-precision tool, I just eyeballed the layout lines, assuring the vertical one was aligned with the side of the milling cutter. I ran the quill down to the bottom line and zeroed the depth gauge on the mill. As I cut, once I got to zero I knew I was deep enough. You could also just eyeball it if you like. Once you start to make cuts like this it’s exciting to see a part start to magically appear from the raw stock.
My milling machine is what I’d call “medium” sized, with a one-horsepower motor. Consequently, I take light cuts even in aluminum and use plenty of cutting fluid when cutting steel. A spray of air now and again will keep chips clear and the cuts cleaner. Aluminum is sort of grabby and tends to collect on the cutter’s edges, so keeping things clean helps the cut along. For around $800 to $1,200, you can get a benchtop mill that can do this sort of work, along with sight dovetails and other light-duty milling. Awfully handy in the home shop! Ditto for the lathe.
At this point, we need to lay out the bolt holes to drill and eventually tap and mill the channels to allow the wrench to “flex” in order to grab the ejector rod as the cap screw is tightened. A step at a time, and soon you’re finished.
At the mill, I clamped the parts onto a piece of flat aluminum stock and cut the channels using an appropriately sized milling cutter. This way, I can cut right through the bottom of the part and into the base metal of the flat stock. Slow and steady wins the race. Remember, those channels could have been cut using a hacksaw, power hacksaw or even filed if you had some patience!
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