Plexiglass Query

So my team has an idea for our bot, however it includes running shafts through plastic. Should we secure bearing flats onto the plastic to run the shafts or are we good to go purely plastic?

if your tolerances are good, and the bore is smooth enough, it will be fine with just the plastic. how do you intend to fabricate it?

a mill (cnc or manual would both work) with a reamer would be ideal, but that can get expensive if you don’t already have the tools on hand.

if you don’t have a mill, a drill press would also get the job done, but in either case a reamer would get you closer to the tolerance you want (and leave a much, much smoother surface finish), since while drill bits would work too, bits are not precision tools. most are made just for roughing- so you’ll want a reamer if you can get one, but it’s not necessary by any means.

-anyways, that would be my advice if you really care about getting this right in an industrial setting. this is just vex so none of it likely matters anyways since v5 motors are so powerful.

just stick a drill bit in a power drill and call it a day lol


Is the polycarbonate going to support the shafts?
Yes - use a bearing block - spinning square shafts will make the holes bigger, that will change the alignment.
No - Make the hole 20% bigger than the shaft so it won’t touch.

Edited to change the material to polycarbonate.


One thing to bear in mind is that “plexiglass” is not legal for competition (as it’s a shattering plastic). You want to be using polycarbonate or one of the other non-shattering plastics mentioned in the game manual (R10).


You could also use the green free spinning inserts instead of the bearing blocks, which should be lower profile.


We’re using polycarbonate, we’re good on the legality


We have the tools for good tolerances. Thanks for the help, I heard something about not needing flats and I was cautious.