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Multi-Axis Spindle Turning
by Reid Gilmore
Applications:
ornaments, bottle stoppers, boxes, pepper mills, etc. (woodgrain aligned
with lathe axis.)
Equipment:
7⁄8˝
diameter Revolving Stebcenter and
7⁄8˝
diameter Stebcenter drive center. Stebcenters are available from several
different woodturning vendors. Check around for best price.
Laying out a 3-axis turning
1. Measure the stock (example is 2˝ x 2˝).
Carefully locate the center (black dot) by drawing diagonals from
the corners.
3. Using the 3-axis turning chart (see below)
look up the stock size to find the drive circle radius (for 2˝ stock
this is 9/16˝).
4. Draw the drive circle (red line) using a
compass.
5. Mark the drive axis (red dots) with an awl.
Drive axis #1 is the intersection of the diagonal and the drive
circle. Place the compass on the opposite diagonal (square red dot)
and mark drive axis #2 and #3. (the radius is 1/6 th
of the circumference, near enough).
6. Using the chart look up the solid circle
radius ( 13⁄16
for 2˝ stock), and draw the blue
circle using the compass. Solid circle radius = drive circle radius
+ 1⁄4˝.
7. Repeat the layout on the opposite. Use the
same measurements if you donʼt want tapered sides.
8. Number the 3 drive axes. For straight sides, #1 is
on the diagonal on both ends. The numbers rotate clockwise on one end
and counter-clockwise on the other. For swirled sides, axis #1 on the
other end is rotated by 120˚.
9. The bottom diagram shows the final shape in green.
When the piece is turned using axis #1 (green dot), the green dashed
line shows the turned circle radius, which cuts the stock at the solid
green line.
Three axis Chart Four axis chart
Multi-axis ornaments are variations on the
standard "globe and icicle" Christmas ornament that was pioneered by Bob
Rosand. Instead of a round or oval-shaped globe that is turned using a
single axis, the multi-axis ornaments are turned with three or four axes
(not something you chop wood with, the plural of axis). The multi-axis
turning method used on these ornaments was demonstrated by Cindy Drozda
at Totally Turning in her 3-sided box demonstration. Step-by-step
descriptions for laying out three-sided multi-axis turnings are included
as part of this article. I have made three sided and four sided
multi-axis ornaments. As you increase the number of sides, the shape of
the turned object starts to approximate a circle. For that reason, I
have not tried a six-sided turning.
The drive centers for a 3-sided multi-axis turning
can be viewed as being at the 4, 8 and 12 oʼclock positions on the drive
circle. Please note that the three drive centers (#1, #2 and #3) rotate
clockwise on one end of the stock, and counter-clockwise on the other
end. If the stock is mounted on the lathe so that the Stebcenter drive
and the revolving tailcenter are both at the 12 oʼclock position, the
turned object will have straight sides that are parallel to the lathe
bed. If the drive center is in the 12 oʼclock position and the revolving
tailcenter is at 4 oʼclock, the turned surface will "swirl" 120° around
the stock. Three and four sided "swirls" are an interesting variation on
the standard round globe ornaments. Because the multi-axis ornaments are
not round, the hollowing step can open "windows" in the sides of these 3
and 4 sided objects. I havenʼt tried making windows in the 3-sided or
4-sided swirls yet, because the swirls I have made arenʼt quite
symmetrical, so the windows would vary in size.
As stock for these ornaments I use 2˝x2˝ turning
stock cut to 1.5˝ - 1.75˝ in length. The grain of the wood needs to be
parallel to the lathe bed. After finding the centers on each end, lay
out the drive circles and solid circles (see instructions). Mount the
stock between centers and use a roughing gouge to remove the corners of
the stock. Use a skew chisel to cut a ¹⁄8˝
wide rabbet down to the diameter of the solid circle radius on each end
of the stock. Mount the stock in a chuck and use a
3⁄8˝
drill mounted in the tailstock to drill a 1⁄4˝ deep hole in one end of
the blank. This will be used to center the piece on a waste block when
the ornament is hollowed.
The stock is now mounted so that the drive center and
revolving center are both at drive center #1. A lathe speed of ~1000rpm
is good for these "off center" turnings and the roughing gouge is the
tool of choice. Since relatively little wood needs to be removed, stop
the lathe frequently if you canʼt see the solid circle rabbet. After the
first side is completed, repeat the process using centers #2 and #3. You
probably wonʼt get a perfectly smooth surface using a roughing gouge,
but with a soft touch, sanding will be minimal. The easiest way to sand
the sides of these ornaments is to start with a belt sander (100 grit)
before moving on to hand sanding.
The multi-axis ornament is now ready for end shaping
and hollowing. With a waste block mounted on a face plate, turn a flat
surface that is roughly 5⁄8˝
to 3⁄4˝ in diameter. Using a 3⁄8˝
drill, drill a 1⁄4˝ deep hole in the waste block. Use thick CA glue and
a 1⁄2˝ long 3⁄8˝
diameter dowel to make a centering post for your ornament. Glue the
ornament onto the centering post and flat end of your waste block. Once
the glue has set, use a spindle gouge to shape the ends of the ornament,
and remove the marks made by the Stebcenters.
To speed up the hollowing process, I use a 3⁄4˝
Forstner bit to make the entry hole and remove a lot of the ornament
center. Small hollowing tools (1⁄4˝ straight and 1⁄4˝ curved scrapers)
are used to complete the hollowing process. If you donʼt want to have
"windows" in the ornament, stop the lathe frequently and check the wall
thickness. The windows are caused by deliberate "overhollowing". The
sides of the windows will have wood splinters, so the shape of the
window needs to be refined with an Exacto knife and sandpaper. If the
multi-axis steps were done carefully (stopping at the solid circle
radius) and you use the centering post method described above, the
windows should be the same size on each of the three faces. The target
weight for the final ornament, including the icicle, is 1 ounce, so I
aim for a ¹⁄8˝
thick wall on these ornaments.
After sanding the ornament you can apply finish while
it is still on the waste block. To remove the ornament from the waste
block, start by using a 3⁄8˝
drill mounted to your tailstock to drill out the dowel centering post.
The ornament can then be removed from the waste block using a parting
tool.
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Posted March 2007 |
