ThunderHex Bearing Explained

[asid61]

Originally Posted by DampRobot

If you can't wait for ThunderHex, and really want to use round bore bearings with hex shaft, you can always use a trick I used to use on 100.

Vex Pro sells metric roller bearings (217-2741) that have an OD smaller than the standard R8 size, and a bore larger than the distance across a hex's flats. We machined inserts for the bearing bore with a 17mm press fit OD and a 1/2" hex ID. If you were to machine a 1.125" OD 26mm ID adapter and press the VP bearing into it, you could basically get a R8 hex bearing where your actual bearing has a round, nonbroached ID.

Even though we put them in applications were they saw a lot of abuse (worm gearboxes), I can't make any recommendations about them being stronger/weaker than existing hex bearings. Because the bearing's race is thinner, I suspect the -2741 bearing is weaker than a hex broached bearing and almost certainly weaker than ThunderHex. YMMV.

That said, it was a cool trick that ended up being pretty useful in some designs. And, if you have a lathe and hex broach, it's a lot cheaper than ThunderHex.

Neat idea!
Alternatively, you can make a rotary broach holder for the lathe and buy a 3/8" hex rotary broach from littlemachineshop forless than the cost of a 3/8" broach.