your rpm indicates your number of poles you have. it is a 4 pole machine. you have 4 run winding coil sets (the heavier looking wire) and 4 start winding coil sets (the thinner looking wire. usually, the run winding is on the outer diam and the start is the inner diam winding.

you say you can fit 8 mags on the rotor. not sure if you mean 2 of them end to end  with the same polarity facing up, 2 beside each other with the same polarity facing up, or 8 of them equaly spaced around the rotor with alternating polaritys.

for a 1/2 hp, i would use them as end to end with same polarity facing up. you likely with have to offset the 2 to try and beat the cogging issue.

The draw back with this is that any case hardening on the jaw will be destroyed, the smallest  size you can hold is now larger, and you will then also have to machine out the small inner bit that the bearing was sitting in, and overcut it by a few thou. If you used a large bearing, a boring bar can do this with the bearing now in the front of the jaws

Without the case hardening, any work that slips in the jaws will destroy the "true" surface, and so will need to be remachined each time you wreck it.... your really only putting off the inevitable, but it's certainly true for a time.

The advantage is that now the case hardening has been gotten rid of, you have a soft jaw chuck, and can (using the same technique) re-machine it whenever you need.

If you use an outer ring (instead of an inner bearing) so that you machine the whole jaw in one action, then the scroll will need to be true, or you will have achieved little.

Caution, the engineer that tought me reckons I'm only a Blacksmith.

north being across from north & south across from south with about 1 round toothpick of space between mags. Does that make sense?

or I could go 6 the same pattern , I would think this would have less out put but be better for cogging? Not 100% sure

As for the lathe it also  came with a 4 jaw chuck as well it is quite a bit bigger but I could change it if they are more accurate.

Thanks for all the input.

  Add pieces of shim stock between the jaws and the bar stock until you get it running true.  With a paint marker, write on each jaw how many thousands of shim is needed for that jaw, so you can quickly shim up any future parts quickly.  (A strip of duct tape will temporarily hold shims in place, but will need retaped occasionally.)

  If you are chucking up on a machined surface, you should always use a copper or brass shim to prevent the jaws from damaging the machined surface anyway, so adding a little more shim material should be that much of a bother.

  A 4 jaw chuck is more precise, because you can adjust each jaw.  A 3 jaw chuck is designed for convenience - it gets you close real fast.

  When I use a 3 jaw chuck, I'm satisfied if I can get a part running within .002 or .003 away from being true.  With a 4 jaw chuck, I try to get a part running within .0005, and have been known to run things running <.0001 runout.