A 21mm hole punch for our single tube HERMS coils. This 21 mm hole punch can be used to make the hole in your kettle for your HERMS coil. Maximum stainless steel thickness: 1.5 mm.
You will need to drill a 10 mm pilot hole for the hole punch. You will also need a 16 mm wrench. In the link above you will find step-by step instructions for the lid hole. Drilling a hole in your kettle will be much the same.
Always drill slowly and wear protection.