ThunderHex Bearing Explained

[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.

[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.

[AdamHeard]

Originally Posted by asid61

Neat idea!
you can make a rotary broach holder

I would wager 99.9% of teams can't just casually make a rotary broach holder.

[MrBasse]

Originally Posted by AdamHeard

I would wager 99.9% of teams can't just casually make a rotary broach holder.

And if you can, why would you not just make the broach as well?

[Cory]

Originally Posted by MrBasse

And if you can, why would you not just make the broach as well?

For the sake of discussion, opportunity cost...a rotary broach holder is over 10x more expensive than a rotary broach. Doesn't make sense to invest that much effort for a $65 tool.

At the same time I don't see the value in making the holder, as it will be worse quality than a COTS one and not work as well, while requiring significant time investment.

[R.C.]

Originally Posted by Cory

For the sake of discussion, opportunity cost...a rotary broach holder is over 10x more expensive than a rotary broach. Doesn't make sense to invest that much effort for a $65 tool.

At the same time I don't see the value in making the holder, as it will be worse quality than a COTS one and not work as well, while requiring significant time investment.

Ditto and you can even get custom sized broaches for about the same price too!

[Dan Richardson]

This is a slick new product Paul, I can see where this would save a ton of time manufacturing drive shafts. Looking forward to getting my hands on some to try it out!

[asid61]

Originally Posted by AdamHeard

I would wager 99.9% of teams can't just casually make a rotary broach holder.

Maybe. I am turning one in a few days/ weeks, so I'll let you know how it goes (tolerance, runout, ease of use, etc.). I've seen a number of guides on making them online.