This is an upgrade to the printable microscope (77450) that allows the user to lock the focus. This is useful if you find the focus difficult to hold due to the weight of the optics tube or if you plan to use a smart phone adapter (coming soon). This upgrade is designed with a tapered nut that is installed from the inside of the head so that adhesives are not required to hold the assembly together. The nut is built separate from the head so that the thread can be reproduced with the best fidelity using fused filament fabrication.
The original microscope can be found here: http://www.thingiverse.com/thing:77450
I printed all the parts using the MakerWare high setting, 0.1mm layers and 15% fill on a MakerBot Replicator 2. Once printed, install the nut from the inside of the head and thread the screw. You should then be able to install the remaining parts from the original design (not included here). Good luck!