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manufacturing quality, part 1

The topic this time is the manufacturing quality of the film loading Leica CRF cameras from M3 to M-A. A totally different story has to be told about the modern so-called ‘digital’ Leica CRF cameras.
There is a persistent story among Leica collectors and users that the M4-2 is a watershed camera between the classical Wetzlar production and assembly procedures and the ‘cost-cutting’ techniques employed since the M4-2 and continuing to the M6 in all its variants and including the current MP and M7 models. There is no discussion yet about the M-A.
The differences observed in the two series (M3 to M4 and M4-2 to MP) are of two sorts: the change of material for some components and the infamous flare patch in the viewfinder due to a change in the construction of the view finder mechanism. The gears of the M3 were made of brass and the gears in later models were made of metal. There is a persistent story, specifically among collectors and historians that brass is the better choice. There is no explanation for this argument. There is also the story, partly true in this case, that the classical Wetzlar method employed much manual labour that gave the finishing touch during the final assembly because of their expertise with the soft hammer and the file to fit the components to extremely close tolerances and the the lavish amount of adjustment screws. The, let us call it, the Canada and Portugal methods follow a more modern method of selective assembly with a minimum of final adjustments.
What is the real story? Every small batch manufacturing process starts with the machining of parts and the assembly of these parts by human labour to a finished product.
Machining of parts to the required dimensions and accuracy depends on the combination of tools and material, on the experience of the operator and on the use of measurement tools to ensure that the machined products are made within specified tolerance ranges. The operator has to fix the metal part in the machine, adjust the tool, select the speed and cooling fluid and inspect the tool to see if it it still fit to work as required. Machining is expensive and time consuming. When labour is cheap, as was the case with the classical Wetzlar method, it makes sense to delegate the responsibility for the final quality to the assembly process. Here it is possible and even necessary to adjust and fine tune the components to a level that satisfies the demands for a precision engineered product.
When leitz shifted production to Midland, all original Wetzlar machines were moved to the Canada location. But most of the original workforce in Germany did not move to the new location. So new personnel had to be trained and some components were treated differently. So some blackening of gears was dropped as not necessary for the durability of the product. Here we see the same process as in the car industry. At first the parts were over dimensioned to make sure they do not break under load, and later it was established that too much metal was used. If we define accuracy as the ability to produce parts within specified dimensions, the blackening of some surfaces is not part of the quality requirement.
In the course of the evolution of machine processing, more accurate parts could be produced, even when using the same equipment. The original brass components had one problem: machining produces heat and the cooling of the parts distorts the dimensions that had to be rectified during final assembly. So new materials that do not deform during cooling were selected. With more accurately shaped parts the assembly process becomes easier and only selective assembly is required. This is more efficient and produces the same or even a better result. The M6 was made and assembled following this process: better machining and less work during assembly. Indeed the M6 has more non-metal parts (some would say ‘plastics’) and some changes of parts (the film counter is stamped and not engraved), but this does not contribute to the ultimate functioning of the camera as a photographic tool. It is an element of nostalgia to lament the disappearance of the classical production method. The functional view is to appreciate the tool as a precision instrument. There are many roads to perfection in manufacturing methods and collectors and historians would be well advised to stay in their field of expertise (finding exclusive models with unknown specs as example) and should not recounting myths about manufacturing methods they do not really understand.