Kubota seems to be all over the place with Zerk size. We have a M59 TLB and it has different sizes and threads on the Tractor, Loader, and Backhoe. I've only had to replace a few in 15 years, but each time turned into a project.
I finally broke down and went to Zoro.com where they have what just might be the world's best zerk thread gauge.... certainly the most expensive at $26.00. So I said, " what the heck" & got one for my mechanical buddy too....
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View attachment 67425