***PLEASE READ B4 USE**** There are steps to doing this right.

I've created a tool for sanding the inside of one of the Paterson tanks. The file is only the un-scaled insert (no hole in it for the dowel). You will want to test a small section of this before you add your own version that fits based on your printer accuracy. I'll lay out the steps to do this successfully...

1. My file is 100% scaled of the original file from the original Thingiverse page, you will have to scale my file down until you have the proper tolerance when adding sandpaper between the tool and the walls of the tank. I did around 94% for sticky sandpaper that comes on a roll. Thicker sandpaper will need around 88-90% scaling due the thickness of paper, but TEST TEST TEST. I used P240 but you may want to go finer, but I'm not sure.

https://www.amazon.com/3M-01683-Stikit-Abrasive-Sheet/dp/B005RMZ4SO/ref=sr_1_11?crid=1H7ZXEW130CTJ&keywords=3m%2Bsticky%2Bsandpaper%2Broll&qid=1648259935&sprefix=3m%2Bsticky%2Bsand%2Caps%2C293&sr=8-11&th=1

1. For a test print: I recommend scaling the file in your slicer down to 30-40mm in Z height. Then print a few versions at various scales until your sandpaper fits well. I recommend purchasing sandpaper on a sticky roll, then you can scale the tool to you liking for the width of the sand paper roll.

2. Once you figure out the XY scale, you will need to make a hole in the model for a dowel. Use digital calipers to measure this. You can always slightly sand the dowel down if its a little tight. I made the insert a final Z height of ~70mm tall, and modeled/removed a hole about 35mm deep into the tool using Rhino 7 (use any CAD software to make the hole AFTER you figure out the tolerance (XY scaling). I attached the dowel with Beacon 3 in 1 craft glue....

https://www.amazon.com/Beacon-Advanced-Crafting-4-Ounce-1-Pack/dp/B001683NAO/ref=sr_1_3?crid=3GBOV7OCHW7FF&keywords=3+in+1+glue&qid=1648259742&sprefix=3+in+1+glue%2Caps%2C268&sr=8-3