So iv been building a cnc, and i was thinking about how to do the linear motion. I had an idea and it seems pretty cheap and easy. im thinking about getting a square bar and bolting down on to my table, then getting a bigger bar (about a half and inch or more), cutting it into two 6" bars, cut them in half so its like a bowl (only square), and then cut holes in it and welding ball bearings in those holes. I dont really know how well this would work, but it seems like it would be cheap and sturdy. Iv made a 5 minute cad scetch, let me know what you think.