It's important to use proper tools when gaping iridium plugs. The cheap gaping tool (pictured below) is not that accurate and can damage the electrode. A damaged electrode can eventually break and wreck your engine.



The proper gaping tool



I didn't have the gaping tool above, instead, I carefully used the vice. If you don't have a vice, you can use a C clamp.

My goal is 0.024. I used .022, .024 and .025 to gap and check.



a deep 16mm to hold the plug in the vice.

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0.022 gauge to check while slowly closing the gap. When I say slowly, I mean 1 "RCH" at a time. It's ok if the 0.022 gets tight, the gap will spring back a little when you take it out of the vice.

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Checking the gap, 0.024 is a go. when checking the gap, don't force the gauge. It should slide in with minimal effort.

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0.025 is a no go.

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If you go past the the desired gap, don't panic. Use pliers to slowly open up the gap, very little effort is needed. Avoid touching the threads and electrode when doing so. While the angle of the picture shows the tip of the pliers touching the electrode, it was far away from it. Additionally, you don't want to repeat this more than you have to. Repeatedly opening and closing the gap might break the tip off.

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Good one.

 

Nice write up

 

I do the same, but I don't actually contact the feeler gauge with the spark plug.

You may dislodge the ever so small sliver of iridium and not even seen it fall off.

You won't know until you drive the car and it pops under boost

 

It won't dislodge if you use the feeler gauge to check the gap, if you use the round tool to open up the gap, yes.

BTW, these NGK's are a lot smoother than the Desno's ikh24 I was running before, at least on idle and during a quick trip around town. We'll see how they last in the long term.