3D to Lathe: Making Woodturning Patterns in SketchUp
David Heim is a Connecticut-based freelancer specializing in books and articles about woodturning and woodworking. He is also the author of the forthcoming “SketchUp Success for Woodworkers” (2018).
About a year ago, I had a great conversation with the two men who run Spring House Press, in Nashville. They asked if I wanted to produce a book of woodturning patterns. I think I said yes before they had finished the question. How could I turn down a chance to combine my love of woodturning with a chance to show off SketchUp’s capabilities? The result, published this July, is Woodturning Patterns: 80+ Designs for the Workshop, Garden, and Every Room in the House.
How to. What to.
Woodturning Patterns is a ‘what-to-do’ book, not a ‘how-to.’ It shows readers more than seven dozen things they can make at the lathe, but generally leaves it up to the readers to decide how to do the turning. Each pattern shows the profile of the turned piece, labeled with every essential length and diameter. Savvy woodturners transfer those measurements to the piece of wood on the lathe, to help duplicate the original.
Each pattern is also accompanied by a 3D representation of the finished piece, so readers know what to shoot for.
The book continues a what-to-do tradition that goes back at least to the time of the Revolutionary War. For more than two centuries, American cabinetmakers and woodturners have relied on pattern books to find shapes for baseboard moldings, chair rails, window and door frames, stairway balusters, newel posts, and so on. Those old books were full of black-and-white engravings, sometimes with measurements but often with nothing but the shape to guide the craftsmen.
I knew immediately I would use SketchUp Pro and LayOut to bring my pattern book into the 21st century. Those programs would let me produce the patterns easily, and the results would be repeatable from one pattern to the next. Here’s how I did it...
Finding good shapes
To get started, I first had to dream up things to turn. The publisher requested lots of patterns for kitchen items:pepper mills, beer taps, bottle stoppers, plus handles for pizza cutters and other gadgets. I added some unexpected things, such as scoops, a French rolling pin, and chopsticks. Then I branched out to knobs and finials, toys and ornaments, tool handles, candlesticks, lamps, vases, platters, and bowls.
Some patterns were under my nose: those pieces I had turned myself. Into the book went a coffee scoop, some small bowls and vases, and a three-sided tool handle (things made at the lathe aren’t always round).
Other pieces required some Internet research. There are very precise specifications for a regulation baseball bat, for example. But I also learned that the organizations in charge of croquet offer a lot of latitude for the size of the mallet head. (Ed note: Go figure!)
For pepper mills and other kitchenware, I tracked down sizes for the grinding mechanism as well as typical specs for pizza cutters, cheese slicers, and the like. Those items have a short metal shaft that’s glued into a hole in the turned wooden handle. I needed to be sure that the handle designs I created would mate nicely with the metal parts. My library yielded more patterns, for knobs, finials, and some bowls. In effect, I used pattern books to come up with some patterns for my book.
Finally, I looked to some of the giants of woodturning for inspiration. Rude Osolnik, who taught for decades at Berea College, in Kentucky, created an iconic midcentury-modern candlestick. I used it as the inspiration for one of the patterns. I did the same for a salad-bowl set, working from designs by the late Bob Stocksdale, a very influential woodturner in Oakland, California. And pieces by Richard Raffan, one of the finest turners working today, gave me the starting point for a baby rattle and a serving platter.
One component per pattern
Whatever the inspiration for a pattern, I began by taking careful measurements from the piece itself, or by importing an image into SketchUp, scaling it to actual size, and using measurements from the image as a basis for modeling.
I created a profile for half the finished piece, using the 2-Point Arc Tool and the Classic Bezier Curve tool from the Bezier Spline plug in. I drew and erased curves until the shape looked right. I made the profile a component, then copied it and made it unique, so I could extrude it without affecting the original. But if the extrusion didn’t look quite right, I’d modify the profile and extrude again.
I got into the habit of copying the profile a second time and scaling it up 100x or 1000x, then extruding the shape. That way, the extrusion wouldn’t have any missing faces.
Once I was satisfied, I copied and flipped the profile so I’d have the full shape, not just half. Then I put the profile and the extrusion in separate scenes, so I could add shadows only to the extrusion.
Dimensions in LayOut
I exported each finished SketchUp model to LayOut, where I added dimensions and labels. Most patterns are scaled to actual size, but the larger patterns are scaled to 75 percent or even 25 percent of actual size so they fit on an 8-1/2 x 11-inch page.
Obviously, accurate dimensions are essential for these patterns. LayOut makes accuracy easy; the challenge was to place the dimensions so the finished drawing would be clear and legible. This was particularly difficult with some complex candlesticks. LayOut’s clipping mask function made it easy to produce inset drawings, where I could put multiple dimensions in a small space.
Once I had completed the dimensions on the profile and positioned the extrusion on the LayOut page, I exported the file as a high-resolution jpeg.
For the last step of the process, I switched to InDesign, Adobe’s page-layout program. (The publisher wanted me to deliver the book as an InDesign file.) The two-page template I created put text on the left and the jpeg of the pattern on the right. Because my LayOut template and the InDesign template used the same page size, I never had to worry that the drawings would be out of scale.
Once I had the pattern in place, I’d type in a title and a couple of paragraphs of text. In some cases, I give a few tips on how to make the turning; for others, I give a nod to the turner who inspired the piece, or some advice on suitable woods to use.
Eighty patterns doesn’t begin to cover everything that can be made on the lathe. I have a hunch that there are more of these books in my future.