Radial Indexing

 The next cut that I need to make on the New Rotor are the radial holes around the periphery of the Rotor.  When I was cutting the radius of the Rotor I was using the Rotary Table as a Rotary Chuck, the idea being the Rotary Chuck holds, and turns the part while the Mill is cutting around the periphery.  In that configuration the Rotary Table was horizontal.

Now I want to Drill Holes from the periphery of the Rotor toward the center of the Rotor.  In this configuration the Rotary Table has to be mounted vertically on the Machine Table, and the machine will be drilling holes into the Rotor in the Z axis.  So, we are still dealing with the three axes of alignment, and a rotary axis.  This time we want X, Y, and rotary axes of movement clamped while we do a Drill operation in the Z axis.  Then I'll loosen the clamp on the rotary axis, move the rotary axis 15 degrees, clamp the rotary axis again, and do another drill operation.

The first obstacle is the Rotor itself.  The Rotor's diameter, four inches, is a little longer than the distance between the center of the Rotary Table, and the vertical mounting surface of the Rotary Table.  This means the Rotor protrudes past the mounting surface of the Rotary Table by about 275 mils. and we need a short riser to get the Rotor above the surface of the machine table.  We need to freely rotate the Rotor around the axis of the Rotary Table to make the peripheral holes.  Also, we need to assemble the Rotary Table assembly on the Drill Press Machine Table, and not on the Milling Table.  When the Milling Table is on the Drill Press there is insufficient vertical clearance to make these peripheral cuts.

Here I have used a 0.375 inch Aluminum plate to be the short riser to get the periphery of the Rotor off the machine table.  The mounting screws are countersinked into the short riser plate so the short riser plate can sit flat on the machine table.  Then I can slide the Rotary Table assembly around the machine table for the X, and Y axes alignment.  There are two C-Clamps that secure the Rotary Table assembly to the machine table once it is aligned.  I have scratched a line around the periphery of the Rotor to indicate the center of the periphery of the Rotor.  I also have some lines on the face of the Rotor which will help with the X, and Y axes alignment.  I used a framing square, the center of the Rotary Table, the Drill bit, and the center line of the periphery of the Rotor to perform the X, and Y axes of alignment of the Rotary Table assembly to the Machine Table, and the Drill.  Blarg...  Thatz a mouthful...

 There is a compass around the edge of the Rotary Table.  Once I had the X, and Y axes alignment locked I rotated the Rotary Table to 0 degrees.  I spent a considerable about of time scrutinizing the X/Y alignment, Rotary Alignment, and depth of cut before I felt confident to make a cut.  The more time you spend fabricating a part, the more valuable it becomes.  As its value increases you feel compelled to overthink each following cut, and don't want to make any mistakes.  This is where it ceases to be a part, and becomes an investment.  Any mistakes could lead to considerable rework, or even scrapping this part, and starting again.

I have made five holes so far, and my process seems to be working well.  At this point I'm going to take a break, and think through this again.  I'll make some measurements on the holes I have cut, and look at the consistency of the cuts.  At first glance it looks like it is going well...