This kit includes all parts needed to replace the OEM RA axis shaft with a stiffer, higher precision shaft which significantly increases the payload capacity of the mount during precision astro-imaging. It can be installed by users who have intermediate level mechanical fitting skills, and simple workshop tools. No machining modification is required.

The OEM shafts in all EQ8 mount types are 55mm OD and made from turned aluminium. The shaft bearings comprise a pair of opposed tapered roller bearings preloaded by an M54 x 1mm cast iron ringnut.

SAE’s replacement RA shaft has nearly identical dimensions but is turned then cylindrically-ground from grade 304 stainless steel. It therefore has 3 times the torsional and bending stiffnesses of the OEM aluminium part, helping raise the maximum imaging payload. The fit to the ID of the shaft bearings is a transition fit, not a clearance fit. The diameter of the most restrictive section of the internal bore through the shaft is increased to aid passing USB Type B connector shells through the mount.

For design reasons, run-out errors in the RA tapered roller bearings have no effect on RA worm gear mesh clearance, and there isno technical justification for exchanging the OEM bearings for a higher precision grade.