Tente Plate Fitting Stem
A variety of Plate sizes are available
It can often be easier to attach the stem plate to the application first and then push-fit the castor (Blind hole) into the bottom stem of the plate
Understand the stem; P41 (type) - 38 x 38 (plate size) / 8 (depth of the bottom stem)
For more information on Threaded Stems click here