Made from 316 stainless steel (because its all i had laying around at the time).
The end of the spindle thread is 2.351 x 1.5mm so thats what i made the end of the extension.
The extension bottoms out on the back of the recess, not against the lock nuts of the machine (theres about .02 clearance).
Once it was done and all cleaned up i lopped on some Never-Seez, hand tightened then grabbed a pipe wrench and gave it alittle extra turn.
Originally this was gonna be a "spider", but when i made it, i never took into account the depth of the removable cover on the machine (the four screws of the spider would have been too close of the out side) and also the piece of stock i started from was the biggest i had (also why its made from 316). In the end i think this will work out better, it can stay on the machine and the cover can be removed with out a problem and now when i use the spider there will not be a chance of buggering up the spindle tube threads, if something happens it will screw up the extension threads.