Using a Copper Backing Strip When Filling Holes by Welding07/17/2019
Q.I have always enjoyed your column in STREET RODDER but I don’t think you answered Stan Collin’s question (in the July ’19 issue) about using a copper backup pad for welding up small holes. You did give some great advice about repairing rusty holes, which I totally agree with. Nevertheless, that copper backing plate technique has been around for years and I would like to know what you think about it.
A.Thanks for pointing out my oversight! I did say that for holes larger than 1/4 inch in diameter, I prefer welding a plug into place. For holes 1/4 inch or smaller, a copper (or copper-faced) backing pad can be a reasonable solution and you can see an example in the photo. I prefer clamping the backing pad into place when possible because that maximizes the ability of the pad to absorb heat from the panel, but sometimes when working in areas with limited access it is feasible to use a backing pad with a long handle on it, and simply press it against the back of the panel by hand as you weld up the holes.
Q.I have a 1963 Oldsmobile Dynamic 88 and I’m reworking the aluminum moldings that go around the A-pillar on the interior. This trim follows the interior from the windshield all the way to the back glass and around it. These pieces were stored away for many years, and to assess their condition I needed to clean them up.
I put them in a dishwasher and let the machine do its work, but after washing the aluminum is dull and dingy and looks like it is caked with hard water.
I have a buffing wheel on my grinder and several assorted sticks of polish, but I haven’t had much luck getting the shine back on these parts. The first piece I worked on looks better than when it came out of the dishwasher, but it does not have the bright shine that it should have. Do you have some ideas for solving this problem?
A.Most automotive aluminum moldings are polished and then clear anodized, which gives them a bright finish that resists normal weathering. I’ve never heard of a detergent attacking an anodized finish, but it’s possible that there were some caustic or alkaline substances in your detergent that degraded the anodizing.
Aluminum is a good electrical conductor but an anodized surface does not conduct electricity. Therefore, you can test your pieces with a voltmeter to see if they are anodized or not. If they are anodized, I believe your best option is to have them stripped (and I would recommend having this done by an electroplating shop) and then they can be polished using standard techniques to attain a mirror-like finish.
I have not found a plating shop that can clear anodize polished aluminum parts and retain the mirror finish, since the standard procedure is to dip the parts in a mild acid cleaning bath in preparation for anodizing. This etches the surface—dulling the polished finish. Of course the auto manufacturers worked out a way to keep the bright polished finish while anodizing trim, but none of the plating shops I have talked with seem to have this capability.
If any of our readers know of a shop that can duplicate this bright anodized factory finish, please let me know. SRM
You can email your questions to Professor Hammer,[email protected], or mail a letter to Covell Creative Metalworking, 106 Airport Blvd., Suite 105, Freedom CA 95019. You will receive a personal reply. Ron Covell has made many videos on metalworking, and they can now be streamed or downloaded from his website. Check these out at covell.biz, along with his ongoing series of workshops held across the nation, or call for a current schedule of workshops and a free catalog of DVDs. Phone (831) 768-0705. Also, check out Ron’s YouTube channel: www.youtube.com/user/covellron.
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