This is not for production bowl turners who merely want to neaten up the bottoms of bowls and platters, but is an essentially no-cost system for turners who want to decorate the bottoms of turnings without being hampered by a live center in the way. Some alternatives to this method include vacuum chucks and special chucks such as the donut chuck, the Longworth chuck and Cole jaws. These are either expensive or time consuming to make and in some cases, cumbersome to use. I have a fully plumbed, remotely switched vacuum system at my lathe, but quite often, I still use the method described here to reverse turn pieces. I find that it often takes more time to set up the vacuum system and center a work piece than to drive a few screws with a cordless screw gun.
Figure 1 shows an example of the system that I have used for countless turnings. It consists of a disk of ½ inch or thicker plywood or particle board with a diameter within the swing capacity of the lathe. Ideally a faceplate would be dedicated to the system. If that is not practical, then a tenon can be turned from a piece of durable wood to fit an available chuck (preferably large-jawed) and screwed and/or glued to the disk. (Note that the disk shown in Figure 1 has been used many times.) The only other components are a few sheet metal screws and some small pieces of ¼ to ½ inch plywood which generally can be reused many times. (I did not have a work in progress at this writing, so the illustration uses a previously completed bowl.) Figure 2 shows the disk that I used to turn the bottom of the 20-inch walnut tray shown my members gallery on this site. Note the 7/8-inch holes; they were bored to allow checking the thickness of the tray as the work proceeds.
The system is used as follows: If a means is available for quickly centering the turning and holding it against the disk temporarily , then the lateral restraint blocks (I generally use four) can be placed snugly against the outside of the rim and fastened with two screws each. If there is no quick reliable way to hold the bowl in a centered position, then pencil several concentric circles on the disk and choose one just smaller than the bowl. Now mount the lateral restraint blocks to just touch the selected circle. Then, with the lathe spinning, use a parting tool to nip away the inner edges of the blocks until the bowl will fit in place. Finally, For plates and bowls with outside edge steepness less than about 60 degrees, install the hold-down strips as shown with a piece of tape or other cushion under them to prevent marring the bowl. If the sides of the bowl are too steep to accommodate the hold-down strips, one can use clear strapping tape wound around the bowl and the disk, while avoiding the area to be turned, to hold everything in place.
The same basic approach and the same components can be used for hollow forms. In these cases, the lateral restraint blocks would be installed on the inside the form. The blocks would be mounted on a circle a bit larger than the opening and then trimmed to fit using a parting tool. Again, clear strapping tape can be used to hold the form snug against the disk. There is another hold-down method that I generally prefer for hollow forms and that ilk. It is described in a companion posting “Simple Hold-down Method for Reverse Turning Hollow Forms and Such”.
In addition to being cheap and fairly fast to use once it has been set up for the first time, this system has other advantages compared to some of the alternatives. They include:
It can be used with porous or holed turnings.
It can be used in some cases with turnings that have fairly large gaps in the rim by positioning the blocks to avoid the gaps.
It can be used for turnings that have gone oval or otherwise distorted, by positioning the blocks appropriately.
Figure 1
Figure2
Figure 1 shows an example of the system that I have used for countless turnings. It consists of a disk of ½ inch or thicker plywood or particle board with a diameter within the swing capacity of the lathe. Ideally a faceplate would be dedicated to the system. If that is not practical, then a tenon can be turned from a piece of durable wood to fit an available chuck (preferably large-jawed) and screwed and/or glued to the disk. (Note that the disk shown in Figure 1 has been used many times.) The only other components are a few sheet metal screws and some small pieces of ¼ to ½ inch plywood which generally can be reused many times. (I did not have a work in progress at this writing, so the illustration uses a previously completed bowl.) Figure 2 shows the disk that I used to turn the bottom of the 20-inch walnut tray shown my members gallery on this site. Note the 7/8-inch holes; they were bored to allow checking the thickness of the tray as the work proceeds.
The system is used as follows: If a means is available for quickly centering the turning and holding it against the disk temporarily , then the lateral restraint blocks (I generally use four) can be placed snugly against the outside of the rim and fastened with two screws each. If there is no quick reliable way to hold the bowl in a centered position, then pencil several concentric circles on the disk and choose one just smaller than the bowl. Now mount the lateral restraint blocks to just touch the selected circle. Then, with the lathe spinning, use a parting tool to nip away the inner edges of the blocks until the bowl will fit in place. Finally, For plates and bowls with outside edge steepness less than about 60 degrees, install the hold-down strips as shown with a piece of tape or other cushion under them to prevent marring the bowl. If the sides of the bowl are too steep to accommodate the hold-down strips, one can use clear strapping tape wound around the bowl and the disk, while avoiding the area to be turned, to hold everything in place.
The same basic approach and the same components can be used for hollow forms. In these cases, the lateral restraint blocks would be installed on the inside the form. The blocks would be mounted on a circle a bit larger than the opening and then trimmed to fit using a parting tool. Again, clear strapping tape can be used to hold the form snug against the disk. There is another hold-down method that I generally prefer for hollow forms and that ilk. It is described in a companion posting “Simple Hold-down Method for Reverse Turning Hollow Forms and Such”.
In addition to being cheap and fairly fast to use once it has been set up for the first time, this system has other advantages compared to some of the alternatives. They include:
It can be used with porous or holed turnings.
It can be used in some cases with turnings that have fairly large gaps in the rim by positioning the blocks to avoid the gaps.
It can be used for turnings that have gone oval or otherwise distorted, by positioning the blocks appropriately.