I've got the sidecar axle mounts just about finished. I just tacked the bosses to the plate so I have to finish weld them but that won't take long. I put them on the mill for the machining - pilot drill, 21/32" drill and then bore to finish diameter of 17mm. Would have been a little quicker if I had a 17mm reamer but it didn't take long. The same procedure for the aluminum spacer between the plates in the photo only on the lathe instead of the mill.
I need to make an axle yet - have to see what I've got around here for material. Eventually the space between the plates will be 7" wide instead of the 3-1/2" or 4" as in the photo. I could move them in closer but I might add a disc brake at a later date and I'll need the room if I do that. When I get the axle machined I'll make a pipe spacer to hold the 7" inside width, snug it together and then tack weld it to the sidecar frame tubing. I'm about ready to tack the frame together, by the way.
Moving right along!