Polishing My 31 Stainless Rad Shell, an update

[Kevin in NJ]

After a lengthy and informative talk to another member and a bit of luck I have moved forward on polishing my shell.

I was trying to decide the best next step. I had fixed dents and leveled with 180/ 220 block sand wet. I needed to take out sanding scratch from a previous polish that was buffed out, plus various scratches since over the whole surface.

I was using 220 PSA 6" sand paper (Pressure Sensitive Adhesive) from Lowes. This cut down below the existing issues. What I nice is you are going dry and you can see the scratches go away. The problem with the PSA disks is they leave behind a mark from the edges that is fairly pronounced.

Next I used Harbor Freight 320 PSA (like $20 for a roll of 100). I could clearly see I was taking out the 220 with the 320 as I went. Still the surface was too cloudly to see all perfectly all the old scratch.

I will take a moment to talk lighting. Flouresent long tube lamps are a help when trying to find problems during the polishing process. I found by moving my head I could find the scratches easily.

Next I did what I know is not a necessary step. I have a roll of 400 PSA from a previous project. So I did cut the surface with the 400. At this point I was stalled. Paper costs about $65 for 100 for the round and I think around $40 for 8X11 sheets. I did not want to spend money from my house budget on car stuff and I needed to figure out the best next step. After a talk with Todd and his experiences and a suggestion to just buy some single disks from the local parts store (did not realize I could do this).

So I went to the local parts store I like and got two each of 500, 600 and 800. I got Norton A275 series norgrip (norgrip means hook and loop (AKA velcro) you need a hook disk on your DA). The velcro backing is better because you do not get a hard edge and you do not get the deeper edge cut you get with a PSA disk.

I did some tests and found 600 gets out the 320. So I decided on 600 and 800 as my next two steps.

I need to add, I got lucky. While out getting parts to fix the lawn mower I picked out of the trash, someone was throwing out a complete windsurf board. So a quick listing on Craigslist and a week later I have $150 of money to spend on car stuff. FWIW, Tecumseh lawn mowers need the rubber bowl gasket and 2 rubber O rings in the carb to get them to start and run right. Also modern lawn mowers have a compression reducer for start. You need to turn the motor backwards to check compression. A bit of a learning curve as the last 4 mowers out of the trash were Lawnboys. - back to the polishing...

So far I have run the 600 grit and very happy with the results. What I found was the finer grit give a better surface to look into and the scratches left from previous grits can be seen. You can get a surprising cut and the life of the paper was better then I had expected. I am also using the center of the paper to had sand some areas. The edges are what get used up when you are cutting with the DA.

Usually I am cutting using the left and right side of the disk. I also found while clearing some deeper defect switching to using the top of the disk changes the cutting action. In some cases I alternated from top and sides.

My next step is to cut with the 800. Then do a test run of 1000 grit. I also bought 2 disks of the 1000 and I think I can go all the way up to 1500.

Now the bad.

Using the DA can ruin the shell if you are not careful. Too much time in one spot will over heat the metal and cause a discoloration and a shink spot. When you need to make a deeper cut to chase a scratch do some then move on to another area. Then come back to cutting the deep scratch.

Now the Judging Standards comments. I can see that an original untouch shell on a new car would only be highly polished on the front and side faces. The curved area going in towards the radiator would not have been polished much if any and it has deep grooves from the forming process. The lower panel was only polished on the front face. I do not think it was polished as bright as we see the shells at the shows. Makes me think the whole shell was likely not so well polished as we commonly see. The area under the paint on the bottom seems to have a satin finish too it and the little bead that goes across the top of the bottom panel did not appear to be polished at all. These are all just observations and may not be exactly correct, just a best guess from looking at my shell.

We will see how well I like the final polish and hopefully I do not mess up anything along the way. I am learning as I go. I do feel a quality hook and loop paper is worth the cost.

[colin1928]

Thanks for posting very interesting reading
will be waiting for the next chapter

[Bill Underwood]

The moral of the story:

Dumpster diving is good!

Thanks for info Kevin

[1932tub]

If you go to 2000 on the sanding discs you can save a step on the polishing mops, may be able to use a white polish on a loose mop then green lime to finish. You can use a little kerosine on the 2000 discs.
I find the best way to inspect the surface is outside on a sunny day.
Make sure you keep you mop lines all in the same direction.

[Bill in SoCal]

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Kevin, Regarding the blue heat mark on stainless steel. There is a cleaner that motorcyclist use on their stainless steel motorcycle exhaust to remove the heat color. Maybe someone hear knows what it is. It might work for you - if you ever have that problem. Sounds like you are having fun - learning new things can be exciting. Bill