I took some parts to rechroming a couple of weeks ago. I had no experience with this shop, but when I got there I saw a lot of work going done, specially for big companies such as beer taps for a big spanish beer brand. That lead me to think they were good as big companies would not give business to people without the proper experience or knowledge.
These are the parts I took

I finally took a couple of covers out -because I had replacement- and this is what I got today. 50 euros for everything you see in this picture.

Looks impressing, doesn't it? But it doesn't stand a close look. There was a lot of pitting visible in spite of the new chrome. I couldn't help not to show my disillusion and asked how come it turned out this way. Have a look at the gas cap

And the carburettor cap

Even the blinker stem was uneven in the surface

I just thought they haven't prepared the parts as they should have, because they should have enough experience to know how a part must be prepared to get a good result. It's true that they guy already warned me that maybe some pitting would remain in the carburettor caps, but I didn't think the blinkers would turn out so bad.
I still believed they didn't prepared the parts well. The guy told me -a guy with a dirty overall and black nails, I mean, a guy who seem to know what he does- that sometimes the pitting is below the chrome, and no matter how much you sand and polish, there is still some pores in the metal that will show up when the part is chromed due to the current. According to what he said, when the part is thin -as the carburettor caps- they can't simply sand because they run the risk to sand across the metal. When the parts are thicker they get good results, and I have to admit that the stem nut and the fork leg caps turned out good, as well as the washers.
Regarding the blinkers and gas cap, he told me they were made out of a material called something like "zamak" and it doesn't take chrome good. I thought it was just bull#$%* because they took good chrome when they were first manufactured. I took some other parts with me for chroming too and was thinking aboug going somewhere else, but this other parts are from my Sanglas bike and they were in a better shape so I just said "WTF, I don't want to look for another chrome shop, let's see how this new parts turn out- and left them.
On my way home I stopped to drink a coffee and had a look at the parts. I noticed two things that escaped me before: the rivet in the center of the carburettor caps were gone, as well as the splines in the blinker body!!!!

I was near the shop so I returned and asked for explanations. the guy told me that he couldn't avoid to ruin the rivets when sanding the caps in the belt sander -that's when I realized they had indeed sanded and polished the parts as he said. According to him, they first remove the chrome, the previous layer -can't remember what was it made of-, gradually sand in two grades, polish to remove the sandpaper scratches, and then rechroming. The missing rivets seemed to prove they were right.
Regarding the blinker splines, he freaked out. The stem had the splines in good condition, but the splines of the blinker body were gone. He told me he did nothing inside, but the zamak doesn't accept chrome so it has to be covered with copper first, and then chrome -that is true because I tried to polish one sometime ago and below the chrome there was copper. According to him, probably the copper had covered the splines. I tried to force the stem inside and the scratches in the body were copper coloured.
Long story short, I spent 50 euros for a gas cap and four blinkers I can't use. Fortunately, it is still cheaper than the two fork caps alone. My question is: have you ever rechromed parts like these? How were your results?