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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 26. | |
| I have obtained quite a quantity of storm-downed applewood. These trees were aged and barely alive before being downed. The wood has a lot of spalting that adds a lot of attractiveness to the bowls made from it. Does the spalting create any health issues in the use of the bowls? I am aware of the respiratory issues involved in the turning and finishing process. | |
| I am not aware of any health issues with using dried, spalted bowls for serving food. At that point, the spores are dry and inactive, the wood finish has sealed the wood surfaces, and any exposure to the spores would be sealed off. Any problem with the spores during the turning process would be long gone. | |
| I have a large, standard steel faceplate that I use regularly. I recently bought a smaller aluminum faceplate that screws onto my drive spindle and it gets stuck snugly repeatedly, despite the use of a lubricant, grease, etc. Everything else works fine—the regular chuck, other faceplates, screw chuck, etc.; I only have a problem with the aluminum faceplate. I think it’s a matter of heat between steel and aluminum, and I just wondered if you had any thoughts on the matter and could offer solutions to alleviate the problem. | |
| I believe the heat transfer from the lathe spindle to the aluminum faceplate is causing the steel to expand more than the aluminum, which causes the faceplate to bind up and to be difficult to remove. The aluminum faceplate is softer metal and binds up when you try to remove the faceplate. The difference in expansion between the two metals may only be a few thousandths of an inch, but this is enough to make removal of the aluminum faceplate difficult. One possible solution would be to send the aluminum faceplate back to the manufacturer and ask them to run a tap of the correct size in and out of the faceplate several times while the faceplate is cold, or ask them to replace the faceplate with a new one—they should be willing to do this. Another option would be to go to an automotive shop and purchase a small tin of valve grinding compound. Apply some compound to the inside threads of the faceplate, and run the faceplate back and forth on the lathe spindle. The abrasive compound may remove enough metal so that the faceplate will go on and off the lathe spindle easily, once the threads are clean inside the faceplate as well as on the lathe spindle. This procedure may need to be repeated several times until the faceplate is opened up enough that it can be easily put on and removed. | |
| I just bought a new chuck and noticed a potential problem. The threads fit okay, but the hub is not long enough to get a good seat on the headstock—it’s about 1/4" shy. My thought was to get a large washer from the hardware store or make a wooden one to make up the difference. Is this a good solution or should I try something else. Is this even a problem worth worrying about? | |
| Whatever the reason, a too-short hub on the chuck or the counterbore is too shallow, the problem needs to be solved. It is essential that the hub on the chuck is secure against the spindle shoulder or consistent accuracy will be lost. It’s not likely that you could purchase a washer from a hardware store to solve this problem. The hole size would not fit and the metal would be too thin, so it would take several washers to do the job and this would likely be unacceptable. I would suggest you make a wooden washer from a hard wood, such as hard maple, to whatever thickness you need. Be sure the washer is thick enough to span the distance between the hub and the spindle shoulder. Another option would be to purchase several washers made from Delrin plastic. They are specially made to help prevent chucks from binding up against the spindle shoulder. Each washer is about 1/16" thick, so it would take four or five to fill the space. It would also be a good idea to use a DuPont washer between the wooden washer and the chuck, if you decide to turn a wooden washer. If the hub counterbore is too short, a good machine shop could make the counterbore deeper so that the hub could register directly against the spindle shoulder. If you decide to do this, it would still be a good idea to use a Delrin plastic No-Lock washer between the hub and spindle shoulder. | |
| What is the difference between using a negative rake scraper or just holding my flat scraper at a negative angle? | |
The negative rake scraper is a relatively new tool to today’s woodturner, but it actually is not a new tool. Instrument makers and woodturners have been using these tools for centuries. These craftsmen have been working with very hard materials, such as ebony, ivory, bone, and blackwood, and these materials were frequently shaped with negative rake scrapers because the surface quality and tool control was excellent. A negative rake scraper cuts with the burr edge and tool control comes from lightly riding the lower bevel. The bevel rubbing the work gives tool control not available with a regular scraper (see Diagram A), which does not ride the bevel. The negative rake scraper is less apt to produce a catch and doesn’t allow the edge to dig in or catch and run, as sometimes happens with a regular scraper. The bevel-rubbing cut does not require the handle position of the tool to be in “trailing position” to minimize catches. The negative rake on the tool allows the cutting position of the tool to be level or a little above the center of the work. A normal scraper will not produce the surface quality of a negative rake scraper unless you turn it on its side and shear-scrape with it. This is difficult to do, as the torque against the tool causes real problems with controlling tool position and the angle of the cut. Trying to do this with a flat scraper will probably cause a major catch and severe damage to the work, and possibly to the turner.
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| Why are metal turning chucks 3-jawed and woodturning chucks 4-jawed? Is it safe to use a 3-jawed chuck on my wood lathe? | |
| Metal working chucks come in many configurations, including 3-jaws, independent jaws, self-centering 4-jaws, and numerous variations of the above. Since the early 1980s, the self-centering 4-jawed chuck has gradually become the standard for woodturners. Many have dovetail jaws which will hold the stock securely, and are available in many sizes and configurations. Sizes range from stock holding as small as 1/4" to jumbo jaws which will hold up to 8-3/8". Today’s chucks are far superior to the 3-jawed chucks many of us were using prior to the marketing of today’s chucks for woodturners. However, a 3-jawed chuck is safe to use on a wood lathe when it is being used by an experienced turner with stock that has been properly prepared. Obviously, three flat jaws will not hold as well as four dovetail jaws, and the small jaw surface will not hold as well as a 4-jawed, larger surface. I do not recommend purchasing a 3-jawed chuck for a lathe, but I have an old one that I use once in a while. |
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| I have been making tops for my grandchildren and have run into problems when I try to decorate the surface with “burn marks.” I have no trouble using a wire to burn spindles, but can’t figure out how to burn the surfaces of the tops. Do you have any ideas? | |
| Wire burning spindles has been around for hundreds of years, and wire burning is a common technique used by today’s woodturners. It is also often used to decorate the outer rims of bowls and platters. However, burning lines on flat surfaces, such as tops or the inside, nearly flat surfaces of plates or platters, is another problem. Prior to woodturning, the surface must be sanded through 320 grit to ensure a smooth, clean surface to display the design. At this point, use a sharp pencil to mark the lines on the spinning piece. If you are not satisfied with the design, sand it off and start over. Once you have determined the design, use a sharp skew chisel, lay it flat on the tool rest, and cut the design lines with the long end of the skew. These lines should be 1/16" deep and 1/32" wide. Now, fold a piece of abrasive paper into a shape that will fit into the cut grooves. With the lathe running at the same speed as for sanding, friction burn the lines with the abrasive paper. Another material to use for burning the lines is a credit card (you probably have a credit card which should be burned anyway). I have also used a hardwood stick, sharpened on the sander to a knife’s edge to fit inside the grooves. If this technique does not produce the effect you want, use a sharp, felt-tipped marker to mark the lines. If you elect to use a marker, be sure to cut the lines so the marker will have a guide to follow; light sanding will remove any unwanted lines or burn residue from the workpiece. | |
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