pic: Drum Roller End Cap (Competition Robot Parts)
 

Re: pic: Drum Roller End Cap (Competition Robot Parts)
 

Is the hex bore made with a rotary broach? It looks much cleaner than anything we've broached with a press.

Re: pic: Drum Roller End Cap (Competition Robot Parts)
 

A rotary broach should have a large chamfer and it does not leave such a clean finish. This is an example of what a roto broached part should look like:

http://cdn3.volusion.com/vyfsn.knvgw...jpg?1442240393

*We (FRC Team) roto broach a bunch of parts since its easy to do and yields good results

Re: pic: Drum Roller End Cap (Competition Robot Parts)
 

Based on some of the other products they are offering I bet it is a custom extrusion (that includes the hex) and is then machined to press fit.

Re: pic: Drum Roller End Cap (Competition Robot Parts)
 

To elaborate on RC's point, the other key factor is the lack of a full form hex. You can rotary broach to a nearly full profile hex, but it's dramatically better for tool life if you have an oversized initial bore. You can see this in the picture RC linked. The center of the flat is missing because the pilot bore is larger than nominal and you're left with just the corners.