I already decided to modify my plans. Instead of going with 6" trucks for all three axis's. I shrunk the z-axis down to 4", and increased the x-axis to 8".

The trucks are built out of 1/8" steel angle, which was then drilled and tapped for 8mm bolts. the bolts were used to hold the bearing assembly.

To aid in drilling the holes, I made a simple jig to hold the angle. The distance from the endpoints wasn't critical, however the distance from the side of the angle was.

I am not sure how well it shows in the image, but my jig is two pieces of scrap wood, nailed together, so the one forms a "wall" to set the angle against. I made a mark at 1" and 1/2", to line the angle against, and drilled away.

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After I drilled the holes in the ends of each piece, I tapped the holes for the m8 bolts I was using to hold the bearing assembly together.

After I assembled the trucks, I realized that I should have painted them to prevent rust. So after disassembly and a quick scrub in soapy water, I gave the pieces of angle a quick coat of spray paint.

Well that is the easy part done. Next I have to build the base plate, and gantry.