I would also add, if MM is your primary unit of measure, then CM = 10*MM. When setting up these base conversion for each system (SI=metric, USC=United States Customary units), you want all of them tied to a single variable if at all possible. So, YARD = 36*INCH. Also, there is the resolution of measurements, so if you make MM the base unit, you can set your MM=RESOLUTION and RESOLUTION=1 as you did on top, or RESOLUTION = 1/87 as below. I am not sure where the 87 came in (unless it was referenced to the XKCD or HO scale), but 1, 0.1, 0.01 are common for metric, and 0.1, 0.001, and 0.0001 are common in American machine shops... Hope this helps. What will really burn your briquette is when you have something that uses metric and non-metric measurements. This all comes down to OpenSCAD being a *unitless* system, and you are introducing units. I am not sure if anyone has provided a units toolbox for OpenSCAD or any of its spinoffs, but it might be worth looking into that. On Mon, Sep 14, 2026 at 7:21 AM Michael Möller via Discuss < discuss@lists.openscad.org> wrote: > Other spelling mistakes in scaling: > https://xkcd.com/3297/ > > man. 14. sep. 2026, 08.28 skrev Michael Marx (spin) via Discuss < > discuss@lists.openscad.org>: > >> For instance: >> >> MM = 1; >> INCH = 25.4*MM; >> FOOT = 12*INCH; >> METER = 1000; >> CM = METER/100; >> ... >> Then set the base unit (MM in this example) as desired to produce the >> final size: >> >> MM = 1/87; >> >> The other units will remain in proportion. >> >> That would of course be METER = 1000*MM; >> >> >> >> >> ------------------------------ >> >> *From:* Jordan Brown via Discuss [mailto:discuss@lists.openscad.org] >> *Sent:* Monday, September 14, 2026 1:11 PM >> *To:* Douglas Ochsner; OpenSCAD general discussion Mailing-list >> *Cc:* Jordan Brown >> *Subject:* [OpenSCAD] Re: Assistance with Some Code (Totally new at this) >> >> >> >> >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org

> For instance: > > MM = 1; > INCH = 25.4*MM; > FOOT = 12*INCH; > METER = 1000; > CM = METER/100; > ... > Then set the base unit (MM in this example) as desired to produce the final size: > > MM = 1/87; > > The other units will remain in proportion. > > > That would of course be METER = 1000*MM; > Oops. Yes, thanks.

Exactly so: https://en.wikipedia.org/wiki/HO_scale On 9/14/2026 11:09 AM, John David wrote: >  I am not sure where the 87 came in (unless it was referenced to the > XKCD or HO scale)