Getting the right tool.
A megohmmeter can be used to verify whether your spindle is still in working condition without internal wiring shorts. This device generates a high-voltage, low-current DC charge to measure resistances, commonly used in electric motor winding or cable insulation tests. The term “ Megger or Megger Tester ” refers to an instrument used to measure insulation in megohms (MΩ), a unit of measurement for cables, transformers, insulators, etc.
Here is an example from Grainger, this is the device used in this guide.
SUPCO, 20 megaohm to 1 gigohm, CAT I, Megohmmeter - 3T105|M500 - Grainger