On 01/04/2011 10:12 PM, crjw wrote: ...
As others have suggested, your printer may not be mechanically aligning the page properly. I can't solve this. But if you have a high quality printer you should be able to properly center everything with a bit of math. An 8.5x11 inch page is 765px x 990px (inkscape always uses 90px/inch). To make things easy your two circles should be centered horizontally at 765/2=382.5px. Vertical alignment may not be necessary but it may make things simpler if you place the two circle centres the same distance from the top and bottom of the page. I have included a sample file below with a pair of 4 inch diameter wheels. Each wheel has eight 2 inch spokes; each spoke is separated by exactly 45 degrees.
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Thanks! Your svg turned on the light bulb :-)
I'm a bit new to Inkscape and I'd completely neglected to set alignment guides. After seeing them in your svg, I've set proper guides for my wheels & will run a few test prints tonight.
Note to Andi: working in inches works as well. px is the default, so that is what I'd been using for finer granularity.