Best Gear, Thread and Knob Generators for 3D Printing

A stripped gear in a mixer, a lost knob on an amplifier, a vacuum hose that is a few millimeters too wide for the sander: these are the jobs where a 3D printer pays for itself, and none of them need CAD. A part generator asks for numbers you can measure, such as a tooth count, a thread pitch or a hose diameter, and draws the part for you.

This guide sorts the largest category on SkipTheCAD by the part you need. We compare the tools on documented features and our own check of each tool page; we have not printed these parts, so print one test part before you print a batch.

Quick answer

• Best gear generator: Koolm’s Gear Generator. Spur, ring, crown, bevel and worm gears plus racks, all from one free MakerWorld form.
• Best gear generator without an account: STLGears. Eight gear types and a free STL, no sign-up.
• Best for designing a whole gear train: Gear Generator 3. Simulate for free; exports need a paid pass or the 45 EUR desktop app.
• Best for screws, nuts and threads: Koolm’s Screw Generator, with the Thread Generator for lead screws and odd thread shapes.
• Best for knobs and caps: Parametric Nut Caps & Knobs System.
• Best for hinges: Maochen’s Hinge Generator, sized from eight measurements.
• Best for brackets: Koolm’s Bracket Generator.
• Best for hose and pipe adapters: Ostat Hose & Pipe Adapter Generators, free in the browser with shapes for named tool ports.

Every part generator we list is on the gears, knobs and parts page.

Which gear generator should you use?

Use Koolm’s Gear Generator if you have a free MakerWorld account, and STLGears if you don’t. Koolm’s Gear Generator covers spur, ring, crown, bevel and worm gears and racks, and spur gears can get round, D, keyway or spline bores and a hub with set screw holes. It works with real gear values such as module and pressure angle, so two gears made with matching settings mesh. STLGears is the quickest route without a login: eight gear types, STL for printing, DXF for laser cutting and no account. Its theory pages explain module and pressure angle if those terms are new to you.

Genstrio is the free, no-account choice when you want the CAD file too. Its gear generator makes spur, helical, herringbone, bevel and worm gears, planetary sets, racks and GT2 pulleys, and it exports STEP for editing in FreeCAD or Fusion as well as STL and 3MF. Its README says the models you make are yours without restriction. The same open-source site also makes pipe and hose adapters, shelf brackets and print-in-place hinges. It has many options per tool, so expect to spend a while learning it.

For fine control over fit, the Ultimate Gear Parametric Generator by ZJUN_3D adds herringbone gears, spiral bevels and a worm with its worm wheel, plus fields for backlash, tip clearance and bore tolerance. Its license rules out selling the prints.

To watch a whole gear train turn before you print it, open Gear Generator 3. Designing and animating spur and helical gears, racks, ring gears, planetary sets, sprockets and belt pulleys costs nothing, but every download needs an export pass: 5 EUR for 7 days, 10 EUR for 30 days or 30 EUR for a year. If you cut gears often, the desktop app for Mac, Windows and Linux is a one-time 45 EUR for a lifetime license with every export included, and it works offline.

More free browser tools fill gaps. Neo Gear makes one spur or helical gear at a time, with profile shift, backlash and root clearance settings and a round, keyed, D, hex or square bore, and it shows the pitch, root and base diameters as you type. It exports STL or 3MF, but has no gear pairs or racks, and the site has no terms on selling prints. The knowhave gear generator makes spur, rack, planetary, bevel and worm sets without an account, and its planetary page shows the drive ratios. It has not been updated in years and has no backlash setting. The alpaco.it Gear Generator makes spur, helical and herringbone gears with an optional matching pinion, with a bore, D-flat, keyway or hub for the shaft. It only launched in August 2026, so there is little outside feedback yet.

For a camera lens, Follow Your Focus makes a geared ring that clamps around the lens for a follow focus unit. You enter the lens diameter or measured perimeter and it works out the tooth count, with M3 or M4 grub screw holes. Its STL files are CC BY 4.0, so you may sell prints if you credit the tool.

How do you print a replacement screw, nut or threaded rod?

Use Koolm’s Screw Generator for standard fasteners. It makes screws, nuts and washers in metric M2 to M24 and inch sizes from #4 to 7/8 inch, with hex, pan, flat and socket heads and several drive types, following ISO, DIN and UTS dimensions. A printed nut can fit a real bolt, but printed threads are far weaker than steel, so keep loads light.

For a lead screw or an unusual thread, the Thread Generator from the same author makes a threaded rod and a matching nut in ISO/UTS, trapezoidal, ACME, buttress or square profiles, with multi-start and left-hand options. For a lost jar or bottle cap, the Threaded Lid Generator needs only four measurements of the neck: the diameter over the threads, the diameter under them, the pitch and the lid height.

Which tools make knobs and caps?

The Parametric Nut Caps & Knobs System covers the most ground. You pick a metric size from M1 to M16 and what the part fits over (a hex nut, an acorn nut, a bolt head, a motor D-shaft or a splined potentiometer shaft), then choose a dome cap, a TPU furniture foot, a screw cover or a knob in styles from knurled and star to wing and T-handle. Press-fit tolerance is a setting, so a second print can fix a loose fit.

For a plain pointer knob on a potentiometer, rotary encoder or appliance control, the D Shaft Knob Generator is simpler. You set the knob size, the D-hole size and depth, an indicator line and one of three bottom styles. Its license does not allow selling the knobs.

How do you make a hinge or bracket that fits your screws?

Start with Maochen’s Hinge Generator. A labeled photo explains its eight measurements, including screw hole size and spacing, so the hinge matches hardware you already own, and it prints in one piece with the pin inside. The pin gap is fixed at 0.3 mm, and recent versions fold back to 270 degrees. For a low-profile hinge on a box or case, ZiMADE’s Flat Hinges Generator makes hinges that open a full 360 degrees and print without supports. Its author suggests a quick tolerance test first, and PETG, ABS or ASA for hinges that see daily use.

For brackets, Koolm’s Bracket Generator makes angle, flat, T and straight brackets with a hole grid for ISO or UTS screws, countersinks included. Both arms share one length setting, so an uneven L is not possible. For shelves, the Any Size Parametric 90 Degree Shelf Bracket sets each leg, the screw positions and the screw head size, and its brace has a slot so you can still reach the screws. To get a laptop charger or router adapter off the floor, bracket.engineer makes a bracket that wraps around a power brick of the size you enter, with screw ears and an optional keyhole slot, to fix under a desk or on a wall. It exports 3MF only and has no license. Printed brackets carry no load rating, so test one under the real load before you trust a shelf to it.

How do you join two hoses or pipes of different sizes?

For dust collection and vacuum hoses, use the Ostat Hose & Pipe Adapter Generators. They run in the browser with no account, and each end is set by diameter, length and taper, measured on the inside or the outside. The full generator adds magnetic and screw flanges, splitters and ready shapes for Dyson, Festool, Makita, Bosch and DeWalt ports. It has far more settings than the basic page, so start there.

PipeFitter builds the part as a chain of straight sections and bends from -180 to 180 degrees, with up to four pipes in one design. Ends can be plain, chamfered, flanged, barbed, toothed or a slip joint, and it exports STL or 3MF. The alpaco.it Hose Adapter Generator is the simplest of the three: two round ends from 10 to 250 mm, each sliding into or over its port, and an elbow up to 90 degrees.

What else can you make without CAD?

The gears, knobs and parts category goes well beyond gears. Koolm’s MakerWorld set also covers print-in-place bearings in more than 60 standard sizes, compression springs and timing belt pulleys for GT2, HTD, MXL and other belts. Other generators make wall plugs, tube end plugs, cable grommets, vent grilles and funnels. The Car Mount Phone Holder Generator fits a car holder to your phone and case, with a built-in USB-C or Lightning dock and Brodit or AMPS mounting on the back, for personal use only. For boxes and project cases, see the box and enclosure generators guide.

How do you measure a part for a generator?

Measure with digital calipers, not a ruler. A generator is only as accurate as the numbers you give it, and a caliper reads to 0.01 mm.

1. Gears: count the teeth and measure the outside diameter across the tips. For a standard metric spur gear, the module is that diameter divided by the tooth count plus 2, so a 32 mm gear with 30 teeth is module 1. Measure the bore and any flat or key on the shaft too.
2. Check the pair: two standard spur gears sit at a center distance of the module times the sum of both tooth counts, divided by 2. Module 1 gears with 30 and 15 teeth sit 22.5 mm apart. If your measured shaft spacing matches, your module is right.
3. Threads: measure the diameter over the threads, then find the pitch. Measure from one thread peak to the peak ten threads further along and divide by ten. An M8 bolt, for example, is about 8 mm across with a standard pitch of 1.25 mm.
4. Shafts: for a D-shaft, measure the round diameter and the distance from the flat to the opposite side.
5. Hoses and ports: measure the inside of a hose and the outside of a port. On a tapered port, measure at the tip and at the base.
6. Print one test part and adjust the clearance or tolerance setting before you print the real thing.

For parts that take a load, print in PETG with extra walls, and add heat-set inserts wherever a screw goes in and out more than once.

Frequently asked questions

Which gear and part generators work without an account?

STLGears, Genstrio, Neo Gear, the knowhave gear generator, the alpaco.it gear and hose adapter generators, the Ostat hose adapter generators and PipeFitter all run in the browser and download without a sign-up. Gear Generator 3 lets you design without an account, but every export needs a paid pass. The MakerWorld customizers, including all of Koolm's generators, are free but need a MakerWorld login.

What has to match for two printed gears to mesh?

Both gears need the same module (or diametral pitch, for inch gears) and the same pressure angle. Helical gears on parallel shafts also need the same helix angle, turned opposite ways. The shafts must sit at the right distance too: for standard spur gears, that is the module times the sum of both tooth counts, divided by 2. Generators that work with real gear values, such as Koolm's Gear Generator and the alpaco.it Gear Generator, give meshing pairs when you use matching settings.

Can I sell parts made with these generators?

It depends on each tool's license. The alpaco.it terms allow selling prints, and PipeFitter (MIT) and the Ostat adapter scripts (GPL-3.0) use open source licenses that allow commercial use. Koolm's Gear Generator is CC BY, but his screw, thread, bracket, bearing, spring and pulley generators need his paid membership before you sell prints. The Ultimate Gear Parametric Generator, Maochen's Hinge Generator and the D Shaft Knob Generator do not allow selling prints. Check the license on the tool's page before you sell.