Tolerance Boolean is a free add-on for Blender that adds a boolean with clearance. Before cutting, it pushes the cutter’s surface outwards (or inwards) along its normals by the amount you set, so a hole for a peg, a socket for a magnet or the gap of a print-in-place joint comes out with the play a 3D printer needs, without scaling or remodelling the cutter.

Why a boolean with clearance

A printed part is never exactly the size of the model: lines spread a little, and two parts drawn to fit perfectly will not fit at all. The usual fix is to scale the cutter, but scaling moves every face by a different amount and distorts long or off-centre shapes. Offsetting along the normals moves every face by the same distance, which is what a clearance is.

Section drawing in three steps: a cutter placed inside a block, the cutter pushed outwards along its normals by the tolerance, and the hole left by the boolean difference, wider than the part by a small gap — Offset the cutter along its normals, then cut: the hole keeps the clearance

What it does

Difference, Union or Intersect, with the Manifold, Exact or Float solver.
Tolerance: the offset along the normals. Positive gives a looser fit, negative a tighter one. The default is 0.2 mm.
Object or collection as the operand. A collection can be placed on the empty that instances it, so a set of cutters you reuse across a model works as one; instances are realized automatically.
Non-destructive. It is a Geometry Nodes modifier: change the cutter, the tolerance or the operation at any time.

How to use it

Select the cutter (a mesh, or an empty that instances a collection), then the object to cut, so that it is active.
Add the modifier from Add Modifier › Generate › Tolerance Boolean. The cutter is set automatically and shown as wireframe.
Set the tolerance and the operation in the modifier panel.

Requirements

Blender	Licence	Install
4.5 or later (tested on 5.2)	GPL-3.0-or-later	Edit › Preferences › Get Extensions › Install from Disk, then choose the zip

Frequently asked questions

How much clearance should I use?

0.2 mm per side is a good start for PLA on a 0.4 mm nozzle; print a small test and adjust. Print-in-place joints usually need a little more than parts assembled by hand.

Is it free?

Yes. Download it below, no sign-in needed. The source code is on GitHub, under the GPL.

Tolerance Boolean – Blender add-on