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Get Ready
Before you begin, let me remind you that lathe duplication is no different from other lathe turning techniques in this respect: You must use safe techniques. Be sure your centers are seated properly; don’t turn at speeds that are too high; when the stock is 3-inches square or larger, cut off the corners to make an octagon; and finally, if you’re gluing up turning stock, be absolutely sure that the glue has cured for 24 hours.
Check the alignment of the duplicator -- all of the alignments. (See Figures 1 and 2.) This is critical to getting good results. If any alignments are off, you won’t be able to reproduce your pattern accurately.
Next, make a pattern or template for the duplicator to follow. You have two choices here -- two-dimensional or three-dimensional. If you wish to make a three-dimensional pattern, turn a spindle using normal lathe techniques. Don’t sand the spindle. Then mount it between the template mounting centers of the duplicator.
To make a two-dimensional template, adhere a paper pattern to 1/4-inch thick hardwood, hardboard, or sheet acrylic. Along with the outside profile, you must also include the centerline of the spindle on your pattern. (You’ll use this later when you align the template in the duplicator.) Cut the outside profile in the template on a bandsaw or jigsaw, then carefully sand the cut edge of the template smooth. This is extremely important! The duplicator will reproduce every little indentation in the pattern, including millmarks, saw kerfs, nicks and chips. Make sure the profile is as smooth as you want the finished workpiece to be. Tip -- You may want to make a trial turning out of scrap wood to test your template. This way, you can discover and correct any problems with the template before you turn good wood. When you’re making your template, there are a few things that you need to consider: If your spindle includes a square section, the template must be wide enough to prevent the cutter from contacting the swinging corners of the stock. To find this distance, measure the square stock diagonally from the centerpoint to a corner. (When you design the pattern, draw the square sections as if one corner was pointing directly at you. If you draw it with a flat face pointing at you, as you normally would, the pattern will be too narrow.)
Use the profile of the cutters to help design your pattern, so that the spindle won’t be outside the realm of what your cutters can cut. Avoid spindle designs with extremely small diameters. This will weaken the stock, causing whip, vibration, and a poor cut. Continue . . . |
