Monday, February 2, 2015

Polishing Aluminum

The side covers were in pretty rough shape. I filled a pit on the timing side case and replaced the primary cover. The replacement primary had a dent which was removed. This is detailed in an earlier post. I cleaned parts up with engine de-greaser and soda blasted them to get all of the gasket sealer off.

Parts were sanded with a rubber block and 120 grit paper to remove heavy scratches and gouges. After getting everything roughed out I went through a succession of increasingly finer papers. Grits used were; 220, 320, 400, 600, 1000 & 1200. Each grit was applied 90 degrees to the grit before it making sure all scratches from the previous grit were removed before progressing to the next step. Kerosene was used to keep the paper from loading. After the parts were sanded to 1200 grit I finished them with aluminum polishing abrasive on a pedestal mounted buffing wheel. The final gloss was obtained using Semichrome aluminum polish applied by a 3 inch right angle air tool and finally by hand. Mother's Billet also works well for the final gloss.

A tedious process....sanding cases. 

Polishing the timing side inner cover in a rubber jaw vice. 

Blocking to keep things flat. 

The final result.


  1. Thanks for this. I've been helping one of my boys with a project restoring his motorbike. We've been using Mothers Mag, but I'd be interested in knowing more about Mothers Billet. I understand that Billet might be better for finer polishing, and Mag for coarser finishes, so it makes sense to use Billet for restoring a bike I guess. Any thoughts?

    Bernice Parsons @ Badger Anodising

  2. Hi Bernice.

    I used Mag in the past but have found that Billet provides a higher gloss. Neither polish is bad but Billet takes away a bit of the cloudiness that Mag will not. Semi-chrome is also a good polish which is comparable to Mag.

    I generally start out on a buffing wheel or with Semi-chrome to see what I have. If I find a lot of scratches I will go to the sand paper process listed in my post, starting with the finest grit that will remove blemishes. If I see no scratches I will step up the finish to Billet without sanding.

    Thanks for the comments and good luck with your restoration. What are you working on?