[SEL] NC or NF thread

[Jack Watson]

Paul Maples wrote:

> Rick, I purchased a NF Grade 8 Bolt and tap but then someone suggested 
> that the threads on a coarse bolts were deeper and when I compared the 
> two taps the coarse thread did have deeper threads so I went with the 
> coarse bolt and tap but ended up welding a bolt to the key itself and 
> pulling it out.
>
> Paul

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Soft material (CI, Al) = coarse thread
Hard material = fine thread

JW²
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