Makeshift Lathe 2

With the castings poured, I needed to machine them. First off was the toolpost base. After cutting the failed bolt off nearly flush with the top, I cut off the sprue and clamped the part in a vice, upside down on the mill. I installed the 7/8" horizontal milling arbor, overarm, and outer support, along with a 1/2" wide, 2.75" staggered tooth cutter I found on eBay. That cutter made quick work of taking down the casting to a flat surface. I was able to take fairly deep cuts, about 0.45" wide with little problem. I milled down far enough to have a nice solid base under both feet where the part would be bolted to the table of the mill.

Next, I drilled the 2 mounting holes in the feet and drilled a 5/8" blind hole in the top for the toolpost. I hand tapped that hole to 3/4" coarse threads. 5/8" is really too small of a hole for a 3/4" tap, but since this was soft aluminum, and becuase I don't have the right size drill for this size tap, I made it work.

The base part was mounted to the mill's table and the homemade toolpost installed. To test my "All it takes to turn aluminum is a sharp stick" theory, I installed a piece of 1/4" square tool steel in the post without any shaping/grinding, just the beveled end from the factory to serve as some relief and gave it a whirl. It cut surprisingly well, although not with the best of results. It did work long enough to true up the casting more or less. I then tried grinding the bit to something resembling a lathe tool off the internet, but that worked about the same. More research was needed before making the final finish passes.

I found some additional info on cutting tools online, and discovered that I didn't have nearly enough back rake on my bit for aluminum. So, I was getting more smear and less cut than I should have. I reground the bit with an eyeballed, more agressive rake and relief angles and tried again. Much improved! It actually cut pretty well, and I went ahead with the final cuts. First, a finish pass across the outer diameter, then a finish facing cut. Next, I made facing cuts to turn down a pilot shoulder to near-size, then some final passes to bring it down to the exact diameter of the pilot on the back of the chuck. Success! The chuck seemed to fit perfectly on the pilot. Now all that's left is to drill 3 holes for the M8 mounting screws to attach the chuck.