Ah no, for using geared lathe the term is "cutting" a thread. The art of thread chasing for fine optical threads were usually "chased", in the classical meaning of the term. In other words, they were cut with a multi-point, freehand tool. They didn't make taps or dies for large-diameter, super-fine-pitch threads. Chasing a thread is quite an interesting skill, but it's not hard to learn from what I hear.

But your point is taken. I cleaned the threads with a tap.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)