Spur Gear Generator
Design a spur gear in your browser from module, tooth count, pressure angle, height and bore settings. Inspect the involute profile and export an STL for your slicer. Start with a matching pair, then check its printed dimensions and fit. Free to use without signup.
How the generator builds your gear
A spur gear has straight teeth parallel to its axis. The generator samples an involute flank from the base circle and builds a mesh from the chosen dimensions. For a standard unshifted external gear, pitch diameter d = m × z and outside diameter dₐ = m × (z + 2), with module m in millimeters and tooth count z. The standard model uses an addendum of one module and dedendum of 1.25 modules. KHK gear calculation reference explains these assumptions.
Profile shift changes tooth thickness and tip/root geometry. It is not a general clearance control: a shifted pair needs its working center distance, contact and interference checked. A small pinion is not automatically suitable for load merely because its preview can be generated.
Choose compatible parameters
For a standard external spur pair, use the same module and pressure angle. Equal module and angle alone do not establish compatibility with bevel gears, arbitrary internal gears or every helical arrangement. The module guide explains the terms; the module calculator converts dimensions and diametral pitch.
Circular, square and hexagonal gear holes use a radius parameter. For a circular 8 mm modeled bore, enter a 4 mm radius. The generator does not automatically add 0.2 mm for printing. Check the allowed bore size and exported geometry; choose any process correction from a measured test.
A worked 2:1 speed reduction
Use a 20-tooth driving pinion and 40-tooth driven wheel at module 2 mm, pressure angle 20 degrees and zero profile shift. Pitch diameters are 40 and 80 mm, and reference center distance is 2 × (20 + 40) / 2 = 60 mm. At 100 rpm input, the wheel turns at 50 rpm in the opposite direction. This kinematic calculation does not establish torque capacity or efficiency.
Use the spur-gear center distance calculator for another pair, then generate both gears with the corresponding values. Keep model settings with your files. A printed pair still needs alignment, backlash, shaft fit and an unloaded hand check.
Printing and export limits
Inspect tooth tips, roots, seams and bores in the slicer. Choose orientation, line width, layer height and material for the actual geometry and use. No universal nozzle/module combination or bore allowance guarantees a working part. The gear printing guide explains a test-first workflow.
STL is a triangle mesh, not a native parametric CAD feature. Use the displayed dimensions when reconstructing a part in CAD and check the application import options. A printable file is not a load rating or a claim that its first physical print has been tested.
Frequently asked questions
Is the spur gear generator really free?
Yes. Every generator on this site is free, without signup or watermarks. The geometry engine is open source, so you can inspect exactly how your STL is built.
Which file format do I get?
The download is a binary STL mesh with a compact GenerateSTL parameter tag for supported round trips. Check slicer preview and dimensions before printing. STL does not contain a native CAD feature tree.
How do I make two gears that mesh?
For unshifted external spur gears, use the same module and pressure angle with reference center distance m × (z₁ + z₂) / 2. Also check interference, alignment and printed fit. A 20-tooth pinion driving a 40-tooth wheel halves the speed; that does not rate the load.
What is the smallest gear I can 3D print?
The useful minimum depends on tooth geometry, print process, material, orientation and required load. Inspect the sliced tooth form and print a test pair. A low tooth count requires an undercut/interference check even when the model exports.
Can I use the STL in Fusion 360 or SolidWorks?
STL is imported mesh data. SOLIDWORKS offers graphics, mesh and some body-import options depending on geometry and settings; this does not restore a parametric gear feature. See the official SOLIDWORKS mesh-import documentation.
Are all gears involute?
No. Other tooth systems, including cycloidal gearing, exist. This tool uses its documented involute-based geometry and straight-sided rack profile. Choose matching tooth systems and check the complete pair instead of assuming any gear shapes can mesh.