Put the numbers in the link
Every parameter is a link parameter; the link below opens the example part. ChatGPT, Claude or any assistant can write one like it from the parameter list (names, units, ranges) at: parameter list (JSON)
Flange generator: a bolt circle plate you can print or machine
Set the bolt circle, the number of holes and where hole 1 sits — the same three numbers as the bolt circle calculator — then the screw, the centre bore and, if you need one, a hub for a pipe or shaft. You get a round flange with exact ISO 273 clearance holes: an adapter plate for an IEC or servo motor face, a printed pipe or duct flange that lines up with a steel one, a hub plate for a wheel or a lazy-susan bearing.
Use it right here
The real generator runs in your browser: set the parameters, then download STEP or STL. Nothing to install, no sign-up.
The first open downloads the CAD engine (about 20 MB).
- - Holes from the bolt circle calculator's convention: hole 1 at the start angle from +X, the rest counter-clockwise
- - ISO 273 fine / medium / coarse holes for M2–M16, plus a print allowance you set
- - Counterbores for ISO 4762 socket heads, a hub for a pipe or a shaft, or a blind flange
- - Refuses what won't hold — holes into the rim, the bore or each other — and tells you what to change
Parameters you can tune
Each parameter below rebuilds real geometry on every change — this is parametric CAD, not a scaled mesh.
| Parameter | Default | Range | What it does |
|---|---|---|---|
| Bolt circle diameterPCD | 65 mm | 10 – 230 | The circle through the hole centres. 65 is an IEC FT65 motor flange and an EN 1092-1 DN15 pipe flange. |
| Number of holesHOLES | 4 | 2 – 12 | Equally spaced. 4 on small flanges, 8 from DN65, 12 on DN200 PN16. |
| Angle of hole 1START_ANGLE | 45 ° | 0 – 359.5 | From +X, counter-clockwise. 45 for 4 holes straddles the centre lines, as ASME B16.5 asks of pipe flanges. |
| ScrewSCREW | M5 | M2 – M16 | Sets the ISO 273 clearance hole (M5 medium: 5.5). |
| Hole series (ISO 273)FIT | medium | fine / medium / coarse | Fine to locate, medium as usual, coarse for loose alignment. |
| Print allowance on holesHOLE_ALLOWANCE | 0.2 mm | 0 – 0.6 | Printed holes come out about 0.2 mm small; set what your printer loses. |
| Screw headsHEAD | plain | plain / counterbore | Counterbore: flat-bottomed, ISO 4762 head Ø + 0.5, as deep as the head is tall, so socket heads sit flush. |
| Outside diameterOUTER_D | 80 mm | 15 – 250 | FT65's 80. Grows by itself when the holes need more rim (half a hole of plastic outside each hole). |
| Centre boreBORE_D | 50 mm | 0 – 220 | 50 is the FT65 spigot Ø; add your print allowance for a fit over it. 0 makes a blind flange. |
| Plate thicknessTHICKNESS | 8 mm | 2 – 20 | Servo flanges run 5–8 mm; 8 takes an M5 counterbore. |
| Hub heightHUB_H | 0 mm | 0 – 50 | A tube around the bore — the socket a pipe or shaft goes into. 0 is a flat plate. |
| Hub wallHUB_WALL | 3 mm | 1.5 – 20 | Shown with a hub. It must stay clear of the screw heads. |
Every parameter can go in the page's link, so one link opens exactly the part you want. Example (6 × M5 counterbored on a 75 mm bolt circle, 20 mm hub for a 21.3 mm pipe):https://www.forgent3d.com/en/generators/bolt-circle-flange-generator?PCD=75&HOLES=6&START_ANGLE=30&HEAD=counterbore&OUTER_D=95&BORE_D=21.5&HUB_H=20
Calculators for this part
Bolt Circle CalculatorHole X / Y for N holes on a PCD, the pitch between them and a drawing — then a printable flange with exactly those holes.Clearance Hole & Heat-Set Insert ChartISO 273 fine / medium / coarse for M1.6–M24, the printed-hole allowance, and insert holes by vendor — then the boss or bracket.
What's in the STEP file
- - The default plate exports as 8 exact faces — 2 planes and 6 true cylinders: the rim, the bore and the four holes — so CAD reads every hole's diameter and position straight off the file, and a CNC quote sees real holes, not a mesh.
- - With a hub and counterbores (the example link) it is 24 faces: 9 planes and 15 cylinders, each counterbore a flat-bottomed cylinder of the ISO 4762 head Ø + 0.5.
STEP AP214 in millimetres, exact B-rep — it opens directly in SolidWorks, Fusion, FreeCAD, Onshape or Inventor, and goes straight into a CNC quote form. STL for the slicer is one click too.
How it compares
| This generator | Typical online STL generator | Vendor CAD library | |
|---|---|---|---|
| Any size within the range | Yes | Yes | Catalog sizes only |
| STEP with exact surfaces | Yes | Usually an STL mesh only | Yes |
| Changes the sliders don't cover | “AI edit” on the page | No | No |
| Account needed to download | No | Usually no | Often |
Let AI change it
Edit with AI on the page
Press “AI edit” in the generator and say what to change — a keyway, holes, a different shape. The AI edits the part's model.py and it rebuilds in your browser, with undo. A few edits a day are free without signing in; to keep the result or go further, copy it into your models and continue with the AI agent.
Edit with AI →Keep going in your workspace
For bigger changes, several rounds, or a part you want to keep: copy it into your models (free account). The Forgent3D AI agent reads the model.py, edits it, rebuilds it and checks the result itself.
Copy and continue with the AI agent →How it works
- 1.Open the generator — the model builds right in your browser, nothing to install.
- 2.Tune dimensions and options in the parameter panel; the geometry rebuilds live in 3D.
- 3.Export STL / STEP for printing — or ask the AI agent for features beyond the sliders.
FAQ
How far from the edge does it put the holes?
At least half a hole of plastic outside each hole (or its counterbore): with a smaller outside diameter the plate grows to that. Steel pipe flanges keep about the same — EN 1092-1 DN15 leaves 8 mm beside a 14 mm hole. For a stronger printed plate, give it 1.5 hole diameters from hole centre to edge; the bolt circle calculator suggests that outside diameter.
Can a printed flange replace a steel pipe flange?
Not under pressure. It lines up with EN 1092-1 or ASME drillings, so it bolts to them — for ducting, low-pressure air, test fixtures, covers and drilling templates. Plastic also relaxes under bolt load: in one test PETG plates lost 11.5 % of their clamp in a week, PLA 3.3 %. Use washers and check the bolts.
How should I print it?
Flat on the bed, hub and counterbores up — no supports. Use more walls than usual (5 or more) and 30 % infill or more so the bolts bear on solid plastic; PETG or ASA for warm places.
How do I make an adapter plate for an IEC FT65 motor flange?
It is this generator's default with a printed fit on the bore: https://www.forgent3d.com/en/generators/bolt-circle-flange-generator?PCD=65&HOLES=4&START_ANGLE=45&SCREW=M5&BORE_D=50.2 — 4 × M5 holes on the 65 mm bolt circle at 45°, Ø50.2 to slip over the 50 mm spigot, 80 mm across, 8 mm thick. Download STEP to have it machined or STL to print.
Can I print a flange that matches an EN 1092-1 DN25 PN16 pipe flange?
Yes: https://www.forgent3d.com/en/generators/bolt-circle-flange-generator?PCD=85&HOLES=4&START_ANGLE=45&SCREW=M12&FIT=coarse&OUTER_D=115&BORE_D=33.7 has the DN25 drilling (4 × M12 on 85 mm, 115 outside). Add HUB_H=30 for a socket the 33.7 mm pipe slides into. Printed, it is for low-pressure air, ducting and fixtures — not a pressure flange.
Can I sell prints made with these generators?
Yes. Models you generate and the STL / STEP files you export are yours: print them, sell the prints, or use them in a product. No attribution to Forgent3D is required.
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