I rebuilt a lift cylinder on a 580K tractor boom today. I used a 1 1/16" socket that worked but seemed a little loose. Is it possible that it's metric?
You must be talking about a loader lift cylinder, cause a boom lift cylinder takes a 1-1/4 bolt, should be a 1-7/8 socket. Loader lift cylinder piston bolt is a 3/4-16 bolt, not metric.
The markings on the bolt head will tell you if it is SAE or Metric. Lines the radiate from the center outward are SAE. If it is marked with something like 10.9 it is Metric. https://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx I have found in my years of working with tools that Snap-On sockets fit bolts the tightest. Matco and Mac are close seconds. Craftsman and other store brand fit a little looser and the cheap Chinese crap from Harbor Freight or Northern fit real loose. I have never rounded off a bolt or nut using Snap-On. I have with Craftsman.
Use only 6 point sockets regardless of the brand you use.