Drilling & Layout Tool

Bolt Circle & Drill Template Generator

Enter your hole pattern and watch it draw itself as a proper dimensioned technical drawing — then print it at true 1:1 size for flanges, wheels, speaker rings, gaskets and mounting plates.

Choose how to continue

Free access gives you the full tool — every field, every layout mode, slotted holes, multiple bolt circles, and Save/Load Project. Full access unlocks the actual SVG/PNG/PDF export files and a downloadable offline copy of the whole tool.

Units

Layout type

Plate dimensions

Bolt circles

Drawing display

Save your work

Export

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100% Scroll or pinch to zoom · drag to pan

To print, use Ctrl/Cmd+P → set Scale to 100% and Margins to None. Measure the small calibration square afterwards — it should come out at exactly 20mm (0.79in). Zooming and panning on screen never affects the printed size.

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About the Bolt Circle & Drill Template Generator

This tool turns a handful of measurements — bolt circle diameter, hole count, hole size, start angle — into an accurate, dimensioned technical drawing you can print and drill straight from. It handles single or multiple concentric bolt circles, round or slotted holes, a centre bore, and an outer plate edge, so it covers everything from a simple 4-hole bracket to a two-ring flange face.

Common uses

How to use it

  1. Choose mm or inch, and optionally a layout preset for quick tips.
  2. Enter your outer diameter and centre bore, if the part has them.
  3. Set the bolt circle diameter, hole count, hole size and start angle — add more bolt circles for flanges with two rings.
  4. Toggle the centreline, hole numbers and dimension labels on or off to suit how you'll use the printout.
  5. Print at 100% scale and check the calibration square with a ruler before you drill anything.

Frequently asked questions

What's the difference between bolt circle diameter (BCD) and pitch circle diameter (PCD)?

Nothing — they're the same measurement. BCD is more common in automotive and speaker-building circles, PCD in flange and mechanical engineering work. Both describe the diameter of the imaginary circle passing through the centre of every hole in the pattern.

Will my printed template actually be true to size?

It's drawn at exact 1:1 scale, but printers and browsers can silently rescale a page. Print at 100% scale with no "fit to page" option, then check the calibration square on the sheet with a ruler before you drill — it should measure exactly 20mm (0.79in). If it doesn't, adjust your print scale until it does.

Can I use this for wheels, speaker rings, flanges and gaskets?

Yes. Pick a layout preset for helpful defaults and tips, or ignore it entirely — every field is manual and works for any circular hole pattern, including flanges with two concentric bolt circles.

Do I have to pay to use this tool?

No. Every input, every layout mode, slotted holes, multiple bolt circles, and Save/Load Project are free with no limits. The one-time payment unlocks the actual SVG, PNG and PDF export files, plus a downloadable offline copy of the whole tool.

Does it work in inches as well as millimetres?

Yes, switch units at any time and every value converts automatically, including the printed dimension labels and the calibration square.