Assuming you don't have a CNC handy, drilling 1-1/8 bearing holes in thin aluminum (<1/4") a step drill works well. You can pilot drill a small hole through the channel to locate the step drill. You don't the spring back or grabbing that you get with a twist drill. For anything under .1" I would recommend a doubler plate to get more thickness.
What I like about the VEX bearing blocks
- You don't have to be near as accurate drilling holes in the channel
- It allows for tension adjustment for belts & chains
- It locates the hole in the Z direction.
- bearing retainer built in
- Greater distance between bearings gives you better support moments.
- smaller holes in channel gives you more strength. (Since you are taking material out of the center, this is a small thing.
The biggest disadvantage is there are a lot more expensive.