Step 2: Making a cube
To make a cube on the milling machine, you first have to dial in your machine. Since this shouldn't be your first project, you should already know how to do that.
So begin by dialling in the milling machine and the vice, then take your aluminium stock and lets get started! It's good to get long stock (my stock was 2x2x6.1) so that you can make multiple cubes at the same time. I made 3 cubes in a little over an hour.
So to begin, we start with our 2x2 stock. Place it in the vice, and hammer it flat so that it is laying flat on the bottom of the vice.
Note: You may need parallels for this step. The vice jaws I used were 1.75 in, and the cube was going to end up at 1.900 in, so I thought that I needed a little more clearance and used parallels. Parallels are also useful, because you can wiggle them to see if the cube is really flat, if they wiggle, then the bottom is not parallel to the bottom of the vice.
The stock begins as 2x2, and we need to get it to 1.900. So 0.050 must come of each side. Begin by touching off with the face mill, and cut 0.050. This should give you a nice machined surface along the top of your stock.
Note: Whenever you make a cut on the mill, you have to deburr your part, so the edges that are built up after cutting don't mess up your squareness. Make a few file passes along each edge after each cut, before you put it back in the vice.
Now, on to side 2! Mark what number each side is on the end with a sharpie, so you can keep track of what's what. Place side 1 against the solid jaw of the vice, and use a planar bar this time to hold it there. This makes it square, because even if side 4 (the one opposite side 1) is all messed up and not square, the planar bar only touches on the point of tangency, and forces all of side 1 to touch the solid jaw of the vice. Since the vice is dialled in and square, and side 1 is smooth since you just machined it, then that forces the face mill to be perpendicular to it, so that when you make the cut on side 2, it ends up perpendicular to side 1!
That was a large explanation, lets just make the cut. Touch off on side 2, and cut another 0.050!
Now, rotate the part 180 degrees, so side 1 is still facing the solid jaw, and side 2 is facing the bottom. At this point, you can check for squareness. The vice should be square, and therefore the part should be square, unless you have a bad vice. If your vice is not square you can fix it by adding shims. If the angle is greater then 90 degrees, place a paper shim on the bottom of the solid jaw, if it is less then 90, place a shim on the top of the solid jaw. This will push the block over, so that the cut will be perpendicular, even though the vice is not. For a more permanent fix, you could mill the faces of the vice square, but be careful, vice faces are usually hardened steel.
When side 1 is facing the solid jaw, and side 2 is facing the bottom, then side 3 is facing up. So measure the cube (side 2-3), and make the cut to get it to size! Should be around 0.050. Use the planar bar again for this cut.
Now, turn the last side (side 4) to the top to cut that as well! Measure, and make your final cut to get side 1-4 to size. Now you have a length of stock with 4 square sides. You don't need the planar bar for this one.
At this point, if you have a long piece like I had, take it to the bandsaw and cut it into chunks. Leave about 0.100 extra to be machined (so you have 1.9 x 1.9 x 2 cubes). Take your cubes back to the mill for the squaring of the last 2 sides.
You can place the cubes beside each other to do them at the same time. Since they were cut at the same time, they will have the same measurements, so the vice will hold all of them equally tightly. Place your blocks in the vice, and use a square to make sure that they are.... square! The vice will hold them tight, and not allow them to rotate around the Z or X axis, but they can still tip side to side and rotate around the Y axis. There is nothing holding them there, so press the square against the bottom of the vice and against the side of the blocks to make them square, and tighten the vice.
Touch off on the top of your cubes, and make a cut so the entire top is a nice machined surface. I can't tell you how much to cut here, just measure how big your cubes are after band sawing, then cut half of that here.
Flip the cubes 180, square them up again, and make your final cut(s) to bring them to size. Now you have some cubes, ready to be turned into more cubes!