Printed jig for metal CNC bearing

It's important to have a well supported linear rail system if you ever intend to cut through thick metal using your CNC mill. It's unfortunate that professionally made bearings can be so [pricey](http://www.amazon.com/Generic-SBR12UU-Router-Linear-Bearing/dp/B00PV6T1GW/ref=sr_1_18?ie=UTF8&qid=1419991660&sr=8-18).

Several makers in the past have come up with great ways to [machine their own homemade railing](http://krazatchu.ca/2012/04/23/on-the-cheap-supported-linear-rail/) from the 1/2" ste