[header] How to guarantee the perfect counterbore process [title] Check your machine tool. [step] The first thing you need to do before you begin machining is to check your machine tool is actually capable of machining an accurate counterbore. To check this, you'll need to run the machine checking feature of your metrology software. 
If the machine benchmark report shows a pass, you can continue onto the next step. If your machine benchmark report shows a fail (see warnings) you must stop machining.