Guide · Flat Wrench Generator

How to 3D print a spanner that fits your nut

Flat Wrench Generator makes a flat spanner for ISO, DIN, JIS, JIS small or inch nuts, from 3 to 40 mm across flats. Each end is open, at 15° or straight, or a 6- or 12-point ring, and the second end can be left off. The opening is the nut, the middle of the ISO 691 play and your printer's measured hole offset, and a fit chip tries four openings on your nut. It is free, prints flat and carries its size on the handle.

FreeUpdated

What can you make with Flat Wrench Generator?

A spanner with one or two ends, from 3 to 40 mm across flats. Makers print:

  • A spare spanner for flat-pack furniture or a bike.
  • A thin key for jam nuts and cone nuts.
  • A ring spanner for a nut that only takes small swings.
  • A spanner in an inch size you do not have.
  • A plastic spanner that will not scratch a painted part.

How do you make a spanner, step by step?

Everything is in the panel beside the spanner, which updates as you change it. Start from a preset, then change what you need.

  1. 1. Start from a preset

    Pick a 10 mm combination, 8 and 10 open, Ring 13 and 17, Thin 13 and 15 or Inch 7/16 and 1/2. A preset sets only the values it names, so your fit stays; Surprise me tries other ends and another thickness for the same sizes.

    Flat Wrench Generator: the presets above the settings, beside the spanner on the print bed.
    The presets and the spanner they make.
  2. 2. Pick the nut and the ends

    Choose the standard your nut follows: ISO, DIN, JIS, JIS small or inch. Each width is named with the threads it fits, so an ISO M10 nut takes 16 mm and a DIN one 17 mm; Custom takes any width. Then each end: open at 15° or straight, a 6- or 12-point ring, or no end B.

    The Ends section: the standard, end A open at 15° and end B a 6-point ring, both 10 mm.
    The standard, the ends and their widths.
  3. 3. Set the body and the label

    Set the thickness, and let the length follow the size (8 × the largest width + 50 mm) or type your own; add a 5 mm hang hole. The label on the handle is the sizes until you type your own, raised, or flush in a second colour on a printer with several filaments.

    The Body section: thickness, automatic length, length and hang hole.
    The spanner's thickness and length.
  4. 4. Find the fit with the chip

    The opening is the nut, the middle of the ISO 691 play and your measured hole offset. Turn on Fit chip: the download adds a small plate with that opening in four steps from −0.1 to +0.2 mm, marked −1 to +2 in tenths. Print it, try them on your nut and set Opening adjust to the step that slides on without rocking.

    The Fit section: Opening adjust with the opening it gives, and Fit chip.
    The opening and the fit chip.
  5. 5. Check it and download

    The checks say whether the heads fit the length, whether the walls are three nozzle lines thick and whether the label fits the handle, with Apply where a setting fixes it. Then download 3MF, with the label in its own colour, or STL.

    The checks, the print figures and Download · free at the end of the panel.
    The checks and the download.

Which spanners can you start from?

Each example opens in Flat Wrench Generator as a new design, beside your own.

Print the spanner flat, as it downloads, so the turning force runs along the layers. It needs no supports. Print it solid: enough walls to fill it, or 100 % infill.

FilamentLayer height to startThinnest wallSupportsNotes
PLA0.2 mm0.8 mmNoneStiff; for hand-tight nuts, not for anything torqued.
PETG0.2 mm0.8 mmNoneTougher than PLA: makers pick it for spanners they use often.

Tips for a printed spanner that holds

  • Use the ring to loosen a tight nut and the open end to run it on: printed jaws spread under load long before a ring does.
  • Pick the standard your nut follows: ISO M10 and M12 nuts take 16 and 18 mm, DIN 934 ones 17 and 19 mm.
  • A 6-point ring grips the flats, the safer choice on a worn nut; a 12-point one takes a new grip every 30° in a tight spot.
  • Keep a steel spanner for anything torqued: a printed one is for hand-tight nuts.
  • Before you print, check it on the view's bar: Dimensions shows its size, Measure the distance between two points, Section cuts it open and Layers steps through it as your printer will.

What if the nut will not go in or the spanner slips?

The nut will not go into the opening
Raise Opening adjust by 0.05 or 0.1 mm and print again, or turn on Fit chip and set the adjust to the opening that slides on.
The spanner rocks on the nut
Lower Opening adjust, and check the standard: a DIN spanner is 1 mm too wide for an ISO M10 or M12 nut.
The open end slips on a tight nut
Printed jaws spread under load: use a ring end, print it solid, and keep it 4 mm thick or more.
The check says the spanner is too short for its heads
Apply turns Automatic length back on, or type a longer length.
The label prints smaller than set
It shrinks to fit the handle: Apply sets letters that fit. When it is too long even at 1 mm letters, shorten it or make the spanner longer.

Is Flat Wrench Generator free?

Yes. Every standard, end and download is free; downloading needs a free NabiMakes account, which also keeps your projects.

  • Free

    Free
    • ISO, DIN, JIS, JIS small, inch and custom widths
    • Open ends and 6- or 12-point rings
    • The label, the hang hole and the fit chip
    • 3MF and STL

Every setting, with its range and default

Lengths are in millimetres. Each setting shows only where it applies: a width only for Custom, end B's size only with an end B, the label's style, size and colour only with a text.

SettingRangeDefaultWhat it does
Ends
StandardISO, DIN, JIS, JIS small, InchISOThe nuts' widths: a new standard keeps each end's nearest width.
End AOpen at 15° or straight, 6- or 12-point ringOpen, 15°The first end's kind.
Size AThe standard's widths, Custom10 mm · M6Across the nut's flats, named with the threads it fits, or Custom.
Width A3–40 mm10 mmA custom width for end A, across the nut's flats.
End BAs end A, or noneRing, 6-pointThe second end's kind, or none for a single-ended spanner.
Size BThe standard's widths, Custom10 mm · M6End B's width, as for end A.
Width B3–40 mm10 mmA custom width for end B, across the nut's flats.
Body
Thickness2.5–12 mm6 mmHow thick the spanner prints; under 4 mm, or twelve layers, it bends.
Automatic lengthOn, offOn8 × the largest width + 50 mm, at least what the heads need, at most 250 mm.
Length50–250 mm130 mmFrom nut to nut, or from the nut to the handle's end; typing one turns Automatic length off.
Hang holeOn, offOffA 5 mm hole at the handle's end, or next to end B.
Label
TextUp to 32 characters10On the handle; it follows the sizes until you type your own.
StyleRaised, FlushRaisedRaised, or flush in a second colour on a printer with several filaments.
Letter height1–50 mm5 mmThe letters' height; they shrink to fit the handle when they must.
Label colour22 optionsBrassThe label's colour in the 3MF.
Fit
Opening adjust−0.2–0.4 mm0 mmAdded to every opening: the nut, the ISO 691 play and your hole offset.
Fit chipOn, offOffA plate with the opening in four steps from −0.1 to +0.2 mm, to try on the nut first.