This part of ISO 10424 specifies requirements for the following drill stem elements: upper and lower kelly valves; square and hexagonal kellys; drill stem subs; standard steel and non-magnetic drill collars; drilling and coring bits. This part of 10424 is not applicable to drill pipe and tool joints@ rotary shouldered connection designs@ thread gauging practice@ or grand master@ reference master and working gauges. A typical drill stem assembly to which this part of 10424 is applicable is shown in Figure 1.