Learn how to read mechanical drawings and fabricate parts to the specified tolerances.
We design our robots in SolidWorks before any final parts are completed; at which point
every part gets a part number and mechanical drawing. That way, it doesn't matter if the parts are machined offsite by a sponsor or in our own shop by students or mentors, as long as they followed the drawing we just accumulate a giant pile of parts, and then over the course of about 7-10 days they all get assembled together.
For practice, try machining keyways into a shaft. For a greater challenge, machine stepped hex and/or keyed profiles into a shaft.
