New Style Probe Port Assembly

I just received the New Style Probe port assembly. I would like to know the best way to drill/punch the 1 1/8" hole Will a step drill work? Is the steel too thick for a knockout punch?
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Yoder_Herb wrote:A step drill would be best. download/Install%20and%20Repair/A91850%20Procedure%20for%20installing%20a%20factory%20probe%20port.pdf