Creepage calculation

Quick question: If I have allowed, say, 12mm of creepage between two pins, and I put a metal screw with a 5mm head in between them, how does this affect the creepage and clearance calculation? The screw is conducting, but electrically isolated as it just screws into a plastic box. I assume that the creepage is now 7mm (3.5mm to screw head from 1st pin, and 3.5mm from screw head to 2nd pin). Is this a valid view?

Mark.

Yes 7mm if the screw is isolated.
You can get non conductive screws.

ronsimpson said:

Yes 7mm if the screw is isolated.
You can get non conductive screws.

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Thanks Ron, makes sense that it would be but you never can tell