Hex/Thunderhex Bearing Ratings

A few years back, there were calls for public RPM and Load ratings for the hex and thunderhex bearings being supplied to FRC teams. Ultimately, it appears that vendor follow through on these requests was mixed at best (kudos to Andymark for providing static and dynamic load ratings for their hex bearings, but even they still need RPM ratings).

With quite a few teams opting for high very RPM flywheel designs this year, it seems like a good time to renew these requests to get actual ratings published for these.


All of the VEXpro round bearings (including thunder hex) are ISO normal class bearings and will have the same ratings as other ISO normal class bearings.

However, any of the hex bearings, from any supplier, should be used with caution on shooter speed type applications. These bearings are rated for when they have round, ground inner races. Putting a hex inner race throws the balance off and I would never use them in a high speed shooter application.


I’m really glad someone who is more qualified than me stated this publicly. I think more teams should consider higher rated round bearings for shooters.

Edit: or thunderhex

What would high speed be, 5000rpm or 10,000rpm. Or would it just be in general for applications where the shaft is spinning fast, you want the bearing to be round.

McMaster thinks that ABEC-1 1/2" bearings are good to about 16.5k rpm. I’d expect Thunderhex bearings to be similar, as 13.75mm is an oddball size.


For something as high RPM as a flywheel shooter, would you have any concern regarding a Thunderhex shaft riding in a Thunderhex bearing? Or would you be more comfortable with turning the ends of the shaft down to be round and getting a proper fit in a round bearing? Would a press fit vs slip fit in the Thunderhex bearing impact your opinion?

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