Needed a way to grip my 25mm conduit for sanding and polishing, that I am using for my MPCNC build (https://www.thingiverse.com/thing:790533). The conduits I bought from screwfix UK (https://www.screwfix.com/p/deta-class-4-conduit-tube-galvanised-25mm-x-3m/7442j) were pretty rough and made a lot of noise when the bearings rolled over them. Now the rods are nice and smooth.
I modified the original design to accommodate the M8 hex screws I had spare and added a few extra cut outs from the expander for a uniform grip. The internal diameter of the tubes were 21mm. The nut and washer was spare parts from my Prusa Mk2s.
Bolt holes might be a little tight. I have left a 0.4mm clearance. If your bolt doesn't go through use a 8mm drill bit to drill to size.
Credits: Although I designed it from scratch I got the idea from The_Cheat (https://www.thingiverse.com/thing:1329637) which I why I'm marking this as a remix.
TIPS: Using the drill counter-clockwise tightens the grip (use it this way for polishing), and drilling clockwise loosens the grip. Makes it useful for insertion, removal, and polishing.
UPDATE: Added a flange to the expander to make it easier to remove.
0.4mm Line Width
3 Lines / Wall
0.15 Layer Height
Printed in PLA