How & Why Our Curves Are Different

Posted on 31 October 2017


If you own a set of inexpensive plastic French curves, you’re probably wondering why the heck we would offer wooden curves at a significantly higher price. You can get a decent set of plastic curves for about $16 to $20; a set of our Design Curves is $37.

It’s not that we dislike plastic. If we could find a material that was better than the specialty bamboo plywood, we’d use it.


Instead, we prefer the unfinished bamboo because it offers the right amount of friction when you are working on paper or directly on a wooden workpiece. For years I cursed my plastic curves because they would slide as I traced around their edges. Our curves stay in place using only light finger pressure.

The second big difference between our curves and typical plastic curves is the small rabbet found on plastic curves. This rabbet is handy when you are inking a mechanical drawing. It prevents the ink from smearing your work.

But in the shop, the rabbet is a nuisance animal. Because of parallax, the rabbet makes it quite difficult to draw an accurate curve. Take the rabbet away, and all you have to do is tilt your mechanical pencil slightly to draw an exact curve exactly where you intended. You might not even know you are struggling with this problem until it disappears.

Finally, we also appreciate how bamboo is an infinitely renewable resource (sometimes annoyingly so) compared to petroleum-based plastics.

— Christopher Schwarz

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  • raney: November 23, 2017

    I forced myself to use ruling pens recently until I finally felt pretty proficient. Then I cleaned them, put them away, and gratefully went back to radiographs.

    they’re nifty tools, and I think they represent an incredible degree of refinement. In practice, though, I completely agree: even if you’re just a now-and-then drafting hack like me there just isn’t much to recommend them over rapidographs. Even that super-snazzy two-line railroad pen you posted.

  • colsdave: November 22, 2017

    I tried using ruling pens when I first started working as a drafter and cartographer close to 40 years ago. There were many lurking in drafting table drawers, both single and double line ones. Setting the pen line width (and double line spacing) consistently and keeping the pen tip’s blades parallel required skills I hadn’t developed. Also, the mylar drafting film we used was far more abrasive than the paper and linen drafting sheets that the ruling pens were used on, and quickly ate the ruling pen point’s fine edges.
    Double point ruling pen showing both adjustable points and spacing adjuster screw.

  • raney: November 22, 2017

    I absolutely get the benefits of the rabbet for ink – which I still do on paper occasionally. But for the shop, we think the ink-edge versions are at best a pain in the butt. So we skipped out on the rabbet (or the even more annoying shallow chamfer – ugh.)

    The universal solution from the days when people still used radiographs, wricos, or even ruling pens (all of which are now shamefully inexpensive on auction sites): add a layer or two of masking tape on the bottom side, which elevates the edge enough to keep capillary effect from sucking your ink under.

  • colsdave: November 20, 2017

    I rather liked the inking rabbet when still using my Rapidograph pens for work. 25 years ago or so…

  • Jim Waldron: October 31, 2017

    Wow, Raney. A triple negative! Outstanding! At least we know CS doesn’t censor/edit your posts. :-)

  • Jason: October 31, 2017

    I hate the ink ledges on my drafting triangles for the very reason you state.

  • Raney Nelson: October 31, 2017

    to be fair – it’s also not that we DON’T dislike plastic…

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