Gear Shift Lever Knob CSX2001-CSX2200 Cobras and very first batch of Tigers

[Dan Case]

I never worked in injection molding, only worked in metal stamping/punching metal parts in dies.

And, as you know, the dies/molds will wear out and need some rebuilding/modifications/grinding to continue production, and there's where you lose the effect of piece parts being totally identical, which will never happen over a period of time.

Our plant was in manufacturing terms a very 'vertical' operation. That means we bought most raw materials and made our own parts. We received millions of pounds of all kinds of materials from many different types of plastic resin pellets to dozens of steel and aluminum materials in large coils.  As you say every part changes slowly as every tool wears and gets serviced.  In our plant, the first few parts from every mold or die after service, even just sharpening of metal working cut stages, required being checked for acceptability. Even if a given dimension was originally statistically 'on nominal' over time it would drift. If in 'tolerance' it was accepted as long as it did not have a problem in performance or for assembly operators. Being on nominal and being in tolerance are almost different subjects if let's say an operator has to bring three stamped metal parts together and fix them to the machine with a single threaded fastener on each end. If all three parts are very close to nominal the screws go in easily. If all the hole locations per part have drifted different ways, all in tolerance, operators can have a rough time doing the installation and that can quickly lead to repetitive motion injuries.   In that case fixing one set of tooling wouldn't be a solution. We had to get all tools and back up tools brought close to nominal.  Personally, I would have changed part and tooling drawings but our global company would not. To them making parts and tools more robust that 'normal' was an extra cost they could never get back. To the company it was up to the plant to put tool upkeep and assembly line issues in our budget in our division and not spread the cost across all the divisions globally.

I will go back to the C3RA "COBRA" emblem example. The original parts had text and symbols on their reverse identifying Ford, the maker, and the maker's mold number. There was no casting date.  Parts made circa late 1965 through 1966 for new 427 Cobras were normally quite nice in appearance quality: no casting flash, no areas of incomplete filling, really fine chrome plating, crisp edges and details, and backgrounds painted nicely. Ford sold countless examples separately and as ancillaries to "Cobra Kits" until circa 1972.  Based on the hundreds I have examined it appears that after Shelby American no longer needed them for new 427 Cobras in 1967 the condition of the mold was not maintained very well, incomplete filling of parts started showing up, details lost their crispness, casting flash was not always polished away, plating quality slipped, and painting quality of the backgrounds got haphazard.  The very fine parts of an expensive sports car in 1966 because a cheap looking do-dad by the time Ford dropped them. Some of the ones people purchased circa 1971 are pretty rough looking things.  Today most sellers don't distinguish between a great looking 1965-66ish part and a rough 1970ish part or the gradient in between.  To most sellers a new old stock emblem is an emblem at a price point. People restoring 427 Cobras often hunt for really nice early parts.  (Said another way, most sellers don't seem to see or maybe just understand the degradation of appearance over the 'production' time period and why not all parts have the same value to everybody.)

[69mach351w]

Great information Dan.

As a past Toolmaker/Machinist, I worked in defense for the Naval shipyard out of Newport News VA. Made parts for carriers and subs.  In the early 80's we had tons of overhaul work as well. Tolerances in tools/molds/machining, were kept tight and checked like clock work. 

So I understand exactly what you're explaining and sure that most here will read and understand as well about molded piece parts and how dies and molds, when not kept up to tolerances, will not produce identical parts over time/usage.

Also, super information about early Cobras and parts.