Casting Aluminum Side Mirror Bases

I received a pair of nice side view mirrors for Christmas but was disappointed when I opened the packages up. The round mirror portion was made of metal but the bases were made of cheap plastic. Since I was going to cast some iron parts, I thought that it would be fun to cast the bases in aluminum.

Plastic base

Mirror right out of the box with plastic base :-(

I took one of the mirror's bases and made a mould using it (I only watched as it took more skill than I have!). The piece is put into a flask and rammed with sand. Then the flask is flipped over and excess sand is removed at the parting line of the template (base). This process is called "coping out" and requires very detailed work.


Here's the original base used as a template


Here's the cast part fresh out of the sand


Here's the casting cleaned up a bit and ready for fine hand sanding

The aluminum is a bit porous, too porous for buffing and it is an incomplete casting. I will have to fill the missing areas with some material to finish it off. I'll have to ask around to see if there is a "liquid aluminum" that I can use. Maybe I can weld on some aluminum? Don't know enough about aluminum to make a decision yet.

The sand that was used was too coarse and should of been finer to give a smoother finish. In the end, I used some body filler to smooth the finish and painted the mirror bases white to match the car body. They came out very nice! In Part 2, I have more details on the actual process of Casting Aluminum Mirror Bases.

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Copyright July, 2011 Eugene Blanchard