Woodturning Design

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Ask Dale is a regular column featured in Woodturning Design. Listed below are the questions and Dale's answers from Issue 7.
Is there a point when a bowl blank becomes too large to turn safely on a chuck and requires the use of a faceplate? What type of screws do you recommend, and is there any formula to determine their length?
The purpose of a faceplate or chuck is to hold the work during the turning process so the shaping can be done safely and efficiently. The method of holding must take into account the weight or mass of the stock as well as the centrifugal force generated by the spinning stock. Typically the larger the surface in contact with the chuck or faceplate, the more secure the work will be. Also, the longer the screws, the more they will hold. If the set-up feels unsafe, it probably is. Select a chuck or faceplate and screws as well as a safe speed with which you feel comfortable. Most bowls are made today using a faceplate, either a screw center or screwed-on faceplate which is fastened to the top of the bowl blank. The assembly is then mounted on the lathe headstock spindle and the outside of the bowl is turned to size and shape. For large bowls, the revolving center in the tailstock is moved into position and advanced to the base of the bowl, making a very secure set-up. Once the outside is shaped, leaving extra wood in the base area, either a tenon or dovetail recess is cut into the base of the bowl to accept the chuck jaws. This is done either in a compression mode, clamping down on a tenon 2" or 3" in diameter and 5/16" to 3/8" long or by expanding into a dovetail recess 2" to 3" in diameter and about 1/4" deep. Both methods should be successful on work up to 3" to 4" thick and 12" in diameter. For larger bowls, it is best to use a larger screw center faceplate and chuck jaws. If in doubt, use a 6" or larger faceplate and sheet metal screws. A faceplate set-up with the diameter of the faceplate one-third to one-half the bowl diameter and four to six screws penetrating the wood from 3/4" to 1" is very secure and will withstand most catches or “dig ins.” However, the faceplate will be on the base of the bowl and may limit the design or shape of the work. With this method of turning, most of the pieces will need to be reverse chucked so the base can be turned and sanded to final shape. Screws should be placed so the holes can be turned away during final turning. I recommend sheet metal screws which are hardened and have a parallel thread for maximum holding power. I prefer the square drive head or, as known in Canada, the Robertson screw. In my shop, I keep a size #12 with lengths 3/4", 1", 1-1/4" and 1-1/2". If a size #12 won’t go through the factory-drilled holes in the faceplate, buy a smaller size such as a #10 or #8 or enlarge the holes in your faceplate to accept the #12 screws. In wet wood, these screws can be driven without drilling pilot holes. For dry wood, it is best to drill a pilot hole to a depth a little shorter than the length of screw penetration into the wood.
Is using dry, seasoned wood best when learning to turn spindles or will “green” wood work better? Is there a particular species of wood that you favor for beginners?
I am assuming the wood selected will be for practice in learning how to use the basic tools for turning spindles and to make the basic cuts commonly used in spindle work. I recommend using 2" x 2" x 12" material, preferably a softwood such as pine. The wood should be reasonably dry, straight-grained, free from knots or other defects, and have 10% to 15% moisture content. Learning how to turn spindles requires attention to detail and proper tool use, so it is best not to use a wood which is difficult to turn. Green wood or unseasoned wood from hardwood sources can be used if it comes from a soft hardwood such as butternut, sassafras, soft maple, box elder, or walnut to name a few. However, the wood should be dry enough to be cut clean and smooth.
My 11-year-old granddaughter has expressed an interest in learning to turn. Would you suggest that I start her out on small bowls, etc., or should I teach her to turn spindles first? What type of projects should I start her on?
Youngsters have a short attention span and want results quickly, so the project of choice should be one which she wants to turn or would like to make. I recommend getting a copy of the book, Classic Woodturning Projects with Bonnie Klein. This book features 12 skill-building designs for turning on mini lathes or any lathe for that matter. The emphasis in the book is on projects that are turned between centers but are not spindles. The center work projects appeal to young people and can be individualized with surface textures, coloring, or burning lines. It is important to maintain a high level of interest, yet stay within the capabilities of the turner. The key to maintaining interest is to successfully turn a high interest project in a short amount of time and do it well. Center work teaches beginners how to use several tools in different ways. Bowl turning can be accomplished with basically a bowl gouge and a parting tool. Spindle work requires a lot of practice to become proficient and, therefore, is not very exciting to a young person. We all can see the advantage of learning how to turn a spindle, but my concern is that enthusiasm and interest will disappear long before proficiency is achieved. The projects in Classic Woodturning Projects would be a great place to start, but read turning magazines such as Woodturning Design for other high interest basic projects.
My spur drive got stuck in the headstock of my lathe and I had a terrible time freeing it. How can I prevent this from happening in the future, and what is the easiest way to free it if it happens again?
When a spur drive gets stuck in the headstock, it presents a frustrating situation. It can usually be removed by using a mild steel rod and a hammer to bang the spur drive loose. When it comes loose, examine the spur drive carefully, checking to see that there are no rough spots or abrasions nor any dirt or grease on the spur drive. Wipe it clean with a rag and solvent. If you find any scoring, take a fine file to smooth the area; then use a fine abrasive paper to polish the surface. The surface of the spur drive must be shiny and smooth. Now examine the Morse taper opening in the headstock quill. This area must be free from any abrasive particles, grit, dirt, dried grease, etc. The Morse taper opening is hardened steel, so it is probably not scarred, just dirty. Thoroughly clean this area until it’s spotless. If necessary buy a Morse taper reamer of the appropriate size to thoroughly clean the hole. It is common practice when turning soft woods to center a spur drive onto a spindle blank by driving the spur drive onto the spindle end to set the spurs and center point. This must be done with the spur drive out of the headstock and driven onto the blank with the blank seated on a firm, hard surface such as a work bench or lathe bed. Use a wooden mallet to prevent mushrooming the end of the spur drive. For hardwoods it is best to saw an “X” on the end of the blank which will accept the spur drive. Then use a mallet to further seat the drive into the blank. NEVER PUT THE SPUR DRIVE INTO THE HEADSTOCK AND POUND THE BLANK ONTO THE SPUR DRIVE.

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