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Convertible Top Well Chrome Molding
#1
runninpony 
As we all know out of the 3 trim pieces of the top well moldings 2 are cast material and 1 is stainless steel. Why was it done that way from the factory? Why not all stainless or all cast?  I've had my 2 cast moldings re-chromed and 1 of them was so badly pitted (according to the chromers, but in my opinion both looked about the same) that they had to put layers upon layers of copper on the part to even out/fill them cavities. Compared to the other molding this one is about twice as heavy as its counter part. I am keeping most of my car's parts in my spare bed room. The heavier molding now has developed a bubble and I have to take it back to the chrome shop when I pick up some of my other parts. It never ends!

71-73 Mustangs never die, they just go faster!
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#2
Mine were in very rough shape, so I had them painted body color. i like the look.

73 ragtop, 1999 Mustang Bright Atlantic Blue Paint, Phoenix Engine 302-335HP,  Edelbrock Carb & Performer manifold; c4 with 2000 stall and shiftkit; 3:55 auburn limited slip differential, Hedman shorties; Car Chemistry Exhaust

Classic Air; Tilt Steering Wheel; 1999 Chrysler Sebring bucket Seats ; power windows;
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#3
(12-23-2018, 05:44 AM)NOT A T5 Wrote: As we all know out of the 3 trim pieces of the top well moldings 2 are cast material and 1 is stainless steel. Why was it done that way from the factory? Why not all stainless or all cast?  I've had my 2 cast moldings re-chromed and 1 of them was so badly pitted (according to the chromers, but in my opinion both looked about the same) that they had to put layers upon layers of copper on the part to even out/fill them cavities. Compared to the other molding this one is about twice as heavy as its counter part. I am keeping most of my car's parts in my spare bed room. The heavier molding now has developed a bubble and I have to take it back to the chrome shop when I pick up some of my other parts. It never ends!

I am sure it all came down to cost.. the contour of the hockey sticks with the bend on either end was hard to stamp in stainless, whereas the straight piece was cheaper to produce in stainless.

I discovered that having the cast hockey sticks re-chromed adds enough metal to the ends that you can't slip the stainless over the end anymore without opening up the end of the stainless piece. Otherwise, my chrome hokey sticks look great.

1973 H Code Convertible - Medium Copper Metallic - June 8, 1973, Built Ford Marketing Sales Vehicle
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#4
Plating over pits - even pits that have been ground down - is a Bad Idea. They should be drilled out, filled with silver solder and then plated. Otherwise they will just come back.

---
Mike
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#5
Ok I can shed some light on both topics stainless and zinc die cast.
I was a tool & die maker and went on into tool engineering for automotive. I served a 10,000 hour apprenticeship in zinc die cast, thermo plastic and thermoset plastic and also metal stamping progressive, transfer and line dies.
Of all the tooling the zinc die cast process yields the most accurate products. Stamping second and Plastic just sucks, lol.
If you build a zinc tool to print with the correct shrinkage built in the parts come out right first trial. Stampings can take months to get right and most plastic is never right, lol.
If you were to make the hockey stick out of stainless you have to do what is called a stretch bend process. The part is usually roller formed to get the general shape. Then you put the blank under tension pull on it and wrap it around a form. NOT VERY ACCURATE for sure.
Ford probably used the cast parts because of assembly issues and fit issues with the roll formed stamping.
Now what causes the pits in the zinc. I worked for Square D, Cutler Hammer, National Lock Cabinet Hardware and all had zinc casting operations. When the molten zinc is shot under hydraulic ram pressure into the tool there is a water jacket in the tooling with cold water to solidify the zinc. When the tool opens it is ejected into a quench tank. The shot then goes into usually a hydraulic press and the flash, runner, sprue and and overflows cut off and put back in the melt. If you put too much remelt in you will make bad parts. If the PH in the quench liquid is wrong it will start the pits to be formed in the brand new part. When the parts go to plating they obviously go through a wash tank, and the normal is copper, nickel and then a few millionths of an inch of chrome. The plating shop should grind out any pits and they actually fill in with lead and then grind and buff and then copper, buff and repeat until all defects are filled then nickel and the flash chrome. Zinc melts at just over 400 deg. F. someone mentioned using silver solder to repair. That will not work silver solder melts between 1,100 and 1,400 deg. F. the zinc would vaporize before you got the silver solder to melt. Some shops skip the copper and just use nickel and chrome.
I will have to find a card there is one place I think in Tenn. that is fantastic on zinc parts.
So don't blame the pitting on salty roads it was a bad initial casting quench process that started the whole thing.
Also how much pressure you shoot the tool at can cause the grain structure to be poor if shot too low. If you break a zinc part you will see a coarse grain inside and fine near the surface of the part.
BTW some people actually put chrome on their stainless to make it have the more white color of chrome.
Ford used lots of stainless trim over the years until our trusty government made them sell their stainless steel mill saying it was too much of a monopoly. Allegheny Ludlum steel was the Co. Over the years Ford made several cars completely out of stainless just playing around.


When a man is in the woods and talks and no women are there is he still wrong??
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David
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