This is an augmented spindle mount for the (stock) rotary tool that comes with the Shapeoko 2. Assembled as designed, the Z axis travel was severely limited due to the top of the rotary tool running into the Z axis thrust bearing plate/motor mount. These inserts fit inside the stock metal mounts and bolt together using the stock 5mm bolts. No additional hardware is necessary. Best of all, this maximizes Z travel: With these mounts I've got 3.25 inches of Z travel (assuming you use a 1/2 inch or longer end mill). This is with the Z-axis makerslide flush with the bottom of the Z carriage. I had significantly less travel with the stock configuration or the other printed spindle holders.
I used a fairly "solid" infill and printed in ABS. It took about 1.5 hours to print all four pieces.
Print out the four pieces:
"Lower Fixed" fits into the metal block on the bottom of the Z axis carrage and "Lower Clamp" holds the Altocraft spindle in place using the stock bolts. The lower clamps are positioned just below the tapered section.
"Upper Fixed" fits into the metal block on the top of the Z axis carrage and "Upper Clamp" holds the Altocraft spindle in place using the stock bolts. The upper clamps are position above the motor brush access screws and below the switch, making sure to leave the cooling vents uncovered. I've found that placing the brush access screws in contact with the underside of the upper clamp works well.
Don't over-tighten. As designed there is a 2mm gap between the pieces. This gap goes to 1mm when tight. I cracked mine by over-tightening it, but it is still working.
Note: I've altered the "Upper clamp" because I see some stress lines developing on the version 0_4. Nothing big, but it will help a little. 0_5 is the new version.