Revised pedal bearings; more info.
I recently overhauled a set of PD-M530 'SLX' SPDs.
These use bindings and bearings that are almost identical to PD-M520 pedals. However, to my surprise the RH bearing has a LH threaded cone and locknut, as seen on a few other (more recent) SPD designs.
I checked the part numbers;
The LH pedal spindle assy (with RH threaded cone and locknut) for both M520 and M530 models is; .....Y-41P98020
The RH pedal spindle assy for M520 pedal (with RH threaded cone and locknut) is;..........................Y-41P98010
The RH pedal spindle assy for M530 pedal (with LH threaded cone and locknut) is;..........................Y-41P98030
The ...30 LH threaded cone/locknut version appears to be indicated with a splodge of blue paint on
a) the retaining sleeve (where you can't see it until the spindle assy is removed from the pedal) and
b) on the cone and locknut itself.
So it would appear that for several newer models of pedal ( the EV techdoc for the M530 pedal is dated 2013) shimano have fitted a revised RH pedal assembly, with a LH threaded cone and locknut, despite the obvious similarities with earlier designs. However for older pedal models they still indicate/supply an older part with a RH threaded cone and locknut.
If anyone needs a replacement RH pedal spindle for PD-M520, PD-M515, etc it is now possible to fit the M530 part instead if desired.
In the event of bearing precession, the RH pedal bearing (with a LH threaded cone/locknut as per PD-M530) is liable to tighten somewhat, but it won't be so likely to break the axle between the cone and locknut as can occasionally happen with a RH threaded cone/locknut assy.
cheers