Drawing polygons to apothem

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Drawing polygons to apothem

Postby jalsina » Mon Mar 17, 2014 5:52 pm

In mechanical drawing, I'm constantly making hex-head machine screws -- imperial, metric, custom, you-name-it. The dimensions of the hexagonal heads are specified by the distance between opposite flats, not the distance between opposite vertices. So far, I've been multiplying the center-to-vertex distance by 1.155, but 1) it's a PITA, and 2) it only works for hexagons -- each polygon has it's own adjustment factor.

Is there a way to get SketchUp to draw a polygon to a specified apothem (radius of an inscribed circle)? In other words, to use the midpoint of a side as the drawing reference point instead of a vertex?

Thanks.
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Re: Drawing polygons to apothem

Postby Dave R » Mon Mar 17, 2014 6:10 pm

That would be nice. I always construct it with guidelines when I need to draw them. You could draw a hexagon of any size and then measure across the appropriate corners using the Tape Measure tool. Make sure you click on both corners and then type the desired dimension. Yes to Resize. If you make a group or component of the hexagon before trying to resize it and then open that for editing, you can resize the hexagon without affecting the rest of the model.
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Re: Drawing polygons to apothem

Postby Box » Mon Mar 17, 2014 6:17 pm

And after making them as Dave suggests, save them as a collection of components so you'll never have to make them again.
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Re: Drawing polygons to apothem

Postby Dave R » Mon Mar 17, 2014 6:22 pm

Indeed!

I thought that went without saying but... ;)
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Re: Drawing polygons to apothem

Postby jalsina » Mon Mar 17, 2014 7:30 pm

Thanks, but when I do as you say -- create polygon, make component, open component for editing, measure with tape measure, and change the dimension -- nothing happens. I get no indication of an option for re-sizing. What am I doing wrong?
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Re: Drawing polygons to apothem

Postby Box » Mon Mar 17, 2014 7:38 pm

You need to use the ctrl key to change from guide to measure.
Basically hitting ctrl with the tape tool toggles a small + on and off. You want it off for the resize function to work.
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Re: Drawing polygons to apothem

Postby Dave R » Mon Mar 17, 2014 7:40 pm

I never hit Ctrl to switch to measuring mode but I do make sure to click at both corners as I mentioned originally. And you need to measure from and to the corners, not from an edge.
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Re: Drawing polygons to apothem

Postby Box » Mon Mar 17, 2014 7:42 pm

D'oh on me, never knew that one, measure the line not the face. :thumb:
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Re: Drawing polygons to apothem

Postby Dave R » Mon Mar 17, 2014 7:47 pm

Or maybe a better way to put it is measure the distance between two endpoints. They don't have to be on the same edge.
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Re: Drawing polygons to apothem

Postby cotty » Mon Mar 17, 2014 7:49 pm

You can find details in the help.
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Re: Drawing polygons to apothem

Postby Box » Mon Mar 17, 2014 7:51 pm

Yep it makes sense and works well, I had always done it the other way with ctrl, then you can measure anywhere and it will resize. Different stokes as they say. Once again, like your signature, you've given me something to reflect on.
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Re: Drawing polygons to apothem

Postby jalsina » Mon Mar 17, 2014 8:01 pm

Works! Thanks. J
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Re: Drawing polygons to apothem

Postby unearthed » Fri Mar 21, 2014 8:56 pm

SD Mitch has a plugin that'll draw polygons by apothem - http://sdmitch.blogspot.co.nz/
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Re: Drawing polygons to apothem

Postby Blenkey » Sat May 11, 2019 9:11 pm

hi its no big deal. Select polygon tool, select centre point when moving out from centre click ctrl, polygon will toggle between corner and centre of line.
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Re: Drawing polygons to apothem

Postby Box » Mon May 13, 2019 9:15 am

Blenkey wrote: click ctrl, polygon will toggle between corner and centre of line.

This feature was added after this thread, so the ctrl toggle of polygons doesn't work in versions before 2015.
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