Measure the part OD
Use a caliper or tape across the widest outside diameter of the gear, bearing, or pulley. Do not substitute shaft diameter for part OD when checking max spread.
Apply a seat margin
GearPull multiplies OD by 1.05 so jaws can seat behind the part. Then it picks the smallest published max-spread class among 3, 4, 6, and 8 in.
Force is out of scope here
Published tonnage on each puller matters for stubborn press-fits, but this calculator only screens jaw spread. Confirm live tonnage and stop if the forcing screw binds abnormally.
Class ladder on this site
Verified VEVOR US 3/4/6/8 in set checked 2026-09-10. Availability UNKNOWN until you confirm the live page. Affiliate tracking is pending.