The hole is bigger than the bolt. Two boards need holding a set distance apart. A cable is sawing itself on a sheet metal edge. All of those are the same part: a tube with a hole down the middle. Give it the two diameters and it builds one, or a plateful.
A bore is safe a little loose: a bolt that rattles still goes through, and you cannot put plastic back. An outside is safe a little tight: it sands down in a minute, and a sleeve that falls out of its hole is scrap. This page sizes them that way round.
That is also why the outside asks whether the hole it goes into was printed. A printed hole shrinks and a printed peg swells, so between two printed parts the whole measured gap applies. Against a drilled hole only your part is wrong, so it takes half.
Those gaps start as four guesses. Print the Tolerance Kit once and they become measurements off your machine, with this spool on it, and the lists here open with your own numbers at the top.
| Material | PETG, or PLA |
| Layer height | 0.15 or 0.2 mm |
| Walls | 3 or more |
| Infill | 40% and up |
| Supports | None |
| Orientation | As downloaded |
It stands on the bed with the axis upright, which is what makes the bore round: printed lying down, a hole comes out flat on top and needs support inside. Nothing here leans past 45 degrees, including the flare under an upper lip.
The first layer squashes out a few hundredths. The lead-in chamfer at each mouth is there to swallow that, and it doubles as the ramp that starts a bolt straight.
The geometry is a small Javascript module. It runs in node as happily as here if you would rather script a whole set of sizes.