We need a special tool here, but dunno where to find what would do the job. Story: we put some some pumps together that are very large, interference fit, and a total prick to put together. The most difficult part is [simplified explanation] drawing a thick spiral metal rod [rotor], down through a rubber spiral lined steel-sleeve [stator]. At the moment, we put a threaded bar into a small tap on the end of the metal rod, then run a thrust-bearing and nut down the threaded bar against a bracket on the end of the â€˜statorâ€™. As the nut winds down against the bracket over the hole in the stator, the nut doesnâ€™t descent: it pulls the threaded-bar through it and out of the stator: bringing the rotor up with it. â€¦ weâ€™d like to do this faster and using less manpower. The ideal tool is a hollow socket that can wind the nut down and allows the threaded bar to come out the back of itâ€¦ or a geared ratchet would do the same â€“ but these are labour intensive as we're talking winding a nut down 3 metres of thread by hand. An air/electric powered version of either of these would be fantastic, however the only company with a solution for us, so far, has said itâ€™d cost $13,000 for them to make the tool to suit â€“ as we need it to accomodate M16 threaded bar through it. Any ideas on something ready-made? Here's a basic pic of what we currently accomplish slowly and with difficulty... the nut and bearing take the load and do the work, not a LOT of torque is required. A pneumatic or electric ratchet would do it fine, it's just that I can't find any that are of a hollow design to allow the threaded-bar through and out the back of them.