threaded connection therebetween it will be appreciated that the pin and box threads may be provided in the lefthand sense so that back rotation would be effected by clockwise rotational movement between the connector members to effect such release since the locking of the pin 10 and box 12 is effected by meshing of the pin threads 32 with the box threads 62 the pin and box connectors may alternatively be joined together by rotation of one connector member relative to the other as the pin is inserted into the box with the key 70 removed in much the same fashion that a standard threaded connection is effected provided sufficient means are available to carry out such rotational movement at the site however the present invention provides that the pin 10 and box 12 may be driven together with considerable longitudinal forces while the pin threads 32 are not meshed with the box threads 62 such pre loading of the connection between the pin 10 and box 12 might not be effected where the connector members are being rotated to effect threaded connection therebetween if the threads in such case are required to bear the load of such longitudinal forces consequently by utilizing fluid pressure to expand the annular region 80 while such loading is effected between the box shoulder 66 and the pin shoulder 28 without contact between the threads 32 and 62 the present invention provides apparatus and method for effecting a threaded engagement between connector assemblies that are pre loaded to an extent that might not be otherwise available the pin and box slots 46 and 68 may be utilized to anchor tools for example.