The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by scibjenkins, Jan 28, 2013.
I don't think I'll be going this year.
Yep. It's always best to metal finish the part as close to perfection as possible.
Yes, unfortunately no real shortcuts. You see a lot of plating with lumpy surfaces, abrasive scratches, pits, roughness in hard to finish areas, etc. Like anything, it's hard to find true craftsmen. And, the better job you do the more work it is, so the more it costs. It comes down to what meets each person's expectations and wallet. Unfortunately, chrome makes imperfections a lot easier to see than most other finish options.
Bugatti front axles were polished steel of the keep at it or it will rust type.
Polishing is the process of removing surface imperfections so that it reflects light rather than absorbs it. The more light it reflects the better it is polished.
When a piece is polished, what we do is to change its surface. We remove surface imperfections by scratching them off with various grits.
We start with a coarse grit and gradually reduce it to finer grits. Each grit has a scratch factor. We work our way from a coarse scratch to one that cannot be seen by the eye. The small particles on the surface become polarized. They line up like soldiers and the surface becomes slightly harder, and more resistant to oxidization, acid and water stains. Water runs off easier, as it is cant get a grip on the polished surface. It is also more resistant to corrosion, just because of its smoothness and its hardness. Of course it will dull with time due to handling and chemicals in the atmosphere.
Corrosion sets in when the ions no longer line up like soldiers. The surface gets attacked by chemicals in the air and the little soldiers start falling by the wayside one by one.
Once the oxidization starts, if left unattended the polished surface dulls and can discolour.
langy, great explanation. Here is an upper motor mount that I made for a chopper frame that was to be chromed, it with all the other parts were polished before welding as it would be easier to do that way. The mount wasn't used and went into a box on the shelf. It has been handled dozens of times as well as mixed up and banging into other parts/brackets in a box, thats were the small abrasions/scratches and rust came from. It was polished over three years ago and it still is very shiny, looks like old chrome.
I love you guys that are far more eloquent than I.
If you are including me on that list, that's only because you have never seen or met me.
Harv I do the very same thing, everything polished first then tig weld and just polish out the welds, makes a much better job
So what kind of grits and what type of paper? Or how do we get to the super polish before chrome or just polish.? I try , but don't have satisfactory results because I don't know what to use , Thanks Jack
It varies with the material and the part, but for most car stuff a uniform 240 grit surface. A skilled metal finisher can normally buff 240 to a show quality finish. With the right buffing wheels and compound it is possible to buff much coarser surfaces to a shiny finish, but there will be waves and lumpiness. Going finer than 240 grit is ok, but the finer the grit, the longer the job takes.
Especially when doing aluminum, use wax, belt grease, or some kind of lube with the abrasives. If that isn't done particles of abrasive can be embedded in the surface. You probably won't see them until they cause problems with the buffing.
Use cloth backed paper. Although other abrasives will work, aluminum oxide is the best compromise for most things.The cloth backing is available in different thicknesses. Depending on the job, one may be better than another.
Hey don't stop there! Polish your shoebox! This pic was from Goodguys Columbus last year. The car was amazing.
I would hate to drive next to that guy. Talk about glare!
Separate names with a comma.