Removing Inside Seam

To get rid of the seam on the inside of the pipe ... I started with my Dremel tool and a small grinding stone. I went back and forth across the seam to cut it down. I did this from both ends. Then I used this monster-big rattail file that is about 5/8" in diameter to wear down the ridge in the part I couldn't reach with the Dremel. When the file slides easily thru from either end ... it slides beautifully onto the axle bar.

Seam Inside Black Pipe

The 5/8" axle won't fit thru the pipe due to this seam on the inside ... otherwise it is a very close fit ... an even better fit than the AN970 Flat Washers that I bought from Aircraft Spruce (got a package of 10 washers).

Tube Cutter

A tube cutter is a handy little tool that should cut a perfect circle around the pipe so you have a reasonably flat end ... I say should because mine wore off a tiny spot and started trying to cut a spiral ... at which point I had to go back to using the hacksaw.

Black Pipe

In order to make hubs for the rear wheels ... so they are removable ... you start with black pipe. You can get this at Lowes or Home Depot in the Plumbing Section. I got mine at Lowes. Click on the image to see a close-up. It is listed as being 1/2" black steel pipe. And comes in various lengths. I got a 30" length because I intend to make 3 sets of hubs and a couple of widgets that will bolt to the axle to hold the disk for the disk brake.