joe greiner
28th September 2007, 06:01 AM
A spiral cage with four captive balls.
Most turners would postpone something like this until they had a little more experience under their belts. Believe it or not, this was my first woodturning, although I use the term "woodturning" with some liberty. I made it about 15 years ago.
I didn't have a lathe at the time. I made a couple "bookends" with dead centers ground from threaded rod, T-nuts, locknuts, and washers. The aft ends of the rods are slotted for screwdriver purchase. I mounted the bookends on a plank, secured a piece of firewood on the centers, and put two narrow strips of lath across the top corners between the bookends. With a straight-cutting bit in the router, I inverted the assembly on my router table against the fence. I twisted the wood, and shifted the sled along the fence, to cut a reasonably accurate cylinder. I used a cove bit to form the ends of the cylinder near the bark, and used the straight bit again to square the outer portion of the ends, with a shallow rabbet on the periphery. I might have done the rabbets as a next-to-final operation later; I don't remember exactly.
I laid out helixes to define the parts to be removed. I set the whole affair on my drill press table, and drilled shallow holes in the outermost inch or so with a spade bit. I did most of the secondary excavation with a small router bit in my Dremel, hand-held; this isn't as bad as it sounds if you maintain a firm two-handed grip on the tool, and clamp the workpiece against rotation. I did more excavation with knives and wood rasps, and sanded the spirals once I had the rough spheres released. I roughly shaped the spheres with the Dremel. As seen in pic4, I went too deep in one spot.
I placed a third dead center through the bottom plank. I modified a spade bit into a two-pronged spur drive, and mounted it in the drill press chuck. Both of these engaged disks of tempered hardboard, dished on one surface to match the desired shape of the balls. While wrestling everything (4 components: the above assembly, one ball, and the two disks) into alignment on the drill press table, one of the spiral limbs cracked in two places. This presented a crisis of conscience: Should I glue the spiral back together and proceed with the original plan? Or should I deftly remove the balls and turn them the easy way? The devil won this battle: I removed the rough balls, taking care to keep them in order to maintain the fiction.
As indicated above, I had no real turning tools, and my only reference for turning a ball was a vague memory of an old article in Popular Mechanics or such. I used a wood rasp for most of the shaping, and finished with sandpaper of various grits. I remounted the ball several times during each stage to shape its entire surface. On the final passes, the dead center reached through its disk and left burn marks on the ball, also shown in pic 4. Finally, I replaced the balls in their original order within the cavity, and glued the cracked spiral. An angel must have been with me too; I can't find the glue lines. I suppose it's just as well that it worked out this way. Even now, if I used the original plan on a real lathe, I'm not sure how I would maneuver a tool rest among the spirals and still have room for a chisel. I suspect I'd use the free-hand rasp again.
To square the entire ends, I set the piece vertically on some short wood strips in the rabbets for a constant height above the router table, and used the staight bit on the end grain. At the time, I only knew of wet finishes. I couldn't envision using them without everything sticking together. So I left it unfinished.
The color in the pictures is off base. My camera has just recently returned from Canon's hospital, and I haven't yet restored the manual color balance. The actual colors have almost no red component.
The species is unknown. Dimensions:
6.25" (160mm) diameter
16.75" (425mm) high
spirals 1.15" (30mm) diameter (sorta round)
balls 2.1" (53mm) diameter.
BTW, pics 1 & 2 are a stereo pair. You can free-view the thumbnails by focusing each eye on them separately, as done with a random-dot stereogram. Applying the same process on the enlarged views takes some image manipulation. Results follow.
Joe
Most turners would postpone something like this until they had a little more experience under their belts. Believe it or not, this was my first woodturning, although I use the term "woodturning" with some liberty. I made it about 15 years ago.
I didn't have a lathe at the time. I made a couple "bookends" with dead centers ground from threaded rod, T-nuts, locknuts, and washers. The aft ends of the rods are slotted for screwdriver purchase. I mounted the bookends on a plank, secured a piece of firewood on the centers, and put two narrow strips of lath across the top corners between the bookends. With a straight-cutting bit in the router, I inverted the assembly on my router table against the fence. I twisted the wood, and shifted the sled along the fence, to cut a reasonably accurate cylinder. I used a cove bit to form the ends of the cylinder near the bark, and used the straight bit again to square the outer portion of the ends, with a shallow rabbet on the periphery. I might have done the rabbets as a next-to-final operation later; I don't remember exactly.
I laid out helixes to define the parts to be removed. I set the whole affair on my drill press table, and drilled shallow holes in the outermost inch or so with a spade bit. I did most of the secondary excavation with a small router bit in my Dremel, hand-held; this isn't as bad as it sounds if you maintain a firm two-handed grip on the tool, and clamp the workpiece against rotation. I did more excavation with knives and wood rasps, and sanded the spirals once I had the rough spheres released. I roughly shaped the spheres with the Dremel. As seen in pic4, I went too deep in one spot.
I placed a third dead center through the bottom plank. I modified a spade bit into a two-pronged spur drive, and mounted it in the drill press chuck. Both of these engaged disks of tempered hardboard, dished on one surface to match the desired shape of the balls. While wrestling everything (4 components: the above assembly, one ball, and the two disks) into alignment on the drill press table, one of the spiral limbs cracked in two places. This presented a crisis of conscience: Should I glue the spiral back together and proceed with the original plan? Or should I deftly remove the balls and turn them the easy way? The devil won this battle: I removed the rough balls, taking care to keep them in order to maintain the fiction.
As indicated above, I had no real turning tools, and my only reference for turning a ball was a vague memory of an old article in Popular Mechanics or such. I used a wood rasp for most of the shaping, and finished with sandpaper of various grits. I remounted the ball several times during each stage to shape its entire surface. On the final passes, the dead center reached through its disk and left burn marks on the ball, also shown in pic 4. Finally, I replaced the balls in their original order within the cavity, and glued the cracked spiral. An angel must have been with me too; I can't find the glue lines. I suppose it's just as well that it worked out this way. Even now, if I used the original plan on a real lathe, I'm not sure how I would maneuver a tool rest among the spirals and still have room for a chisel. I suspect I'd use the free-hand rasp again.
To square the entire ends, I set the piece vertically on some short wood strips in the rabbets for a constant height above the router table, and used the staight bit on the end grain. At the time, I only knew of wet finishes. I couldn't envision using them without everything sticking together. So I left it unfinished.
The color in the pictures is off base. My camera has just recently returned from Canon's hospital, and I haven't yet restored the manual color balance. The actual colors have almost no red component.
The species is unknown. Dimensions:
6.25" (160mm) diameter
16.75" (425mm) high
spirals 1.15" (30mm) diameter (sorta round)
balls 2.1" (53mm) diameter.
BTW, pics 1 & 2 are a stereo pair. You can free-view the thumbnails by focusing each eye on them separately, as done with a random-dot stereogram. Applying the same process on the enlarged views takes some image manipulation. Results follow.
Joe