limited to a particular arrangement for allowing selective translation of the retention members 106 within the retention member bores 124 a skilled person will appreciate that other arrangements for allowing selective translation of retention members within retention member bores can be used in place of the threaded arrangement one example of such other arrangements is a twist lock arrangement where a retention member is slid to a depth in the respective retention member bore where it is engaged with respective engagement pins and is then locked in place by being twisted a fraction of a complete rotation in such an arrangement it can be useful to implement some form of anti rotation mechanism to prevent unintentional rotation of the retention member another example of such other arrangements is where a retention member is slidably and captive disposed within a respective retention member bore being spring biased in the engagement direction such to it is manually displaced to in the disengaged position for along the an engagement pin to be fully inserted within a respective engagement pin bore with respect to attaching the adapter 104 to the drilling head equipment a surface 136 adjacent a central bore 137 of the adapter 104 fig4 and 5 includes a plurality of fastener bores.