Abrasive mediums used in pre-polishing for production chrome?

First of all, it's nice to find a concentrated knowledge base on the subject of industrial finishing.

I own an aftermarket motorcycle component company. One of our recent hurdles in a mfg process is one of our products needs to be pre polished prior to welding. (prominently visual surfaces are inaccessable after assembly) Our material to be polished is 1" mild tubing and 7/16 mild rod. Currently, we have been experimenting with 21" X 7/16" rod in a lathe, using 250 then 500 sandpaper then a polishing compound applied with a soft cloth. While the lathe type operation seems to be sufficient, I'm certain there are more effective abrasive mediums we should be utilizing. Any suggestions would be greatly appreciated.

Thank you.

Your parts are long for most standard mass finishing systems, but it can be done if you have enough volume to afford the machine system. Another possible alternative is what is called a drag finishing machine system. Lastly, you might want to look at a semi-automated buffing system, something like a pass through.