Powermatic 3520B - Manual (Page 26)

26
As you turn bowls from green wood, make sure
you maintain a consistent wall thickness
throughout the piece. Leaving a piece thick in
some areas and thin in others will cause the
wood to dry unevenly and promote checks and
cracks.
Distortion
Distortion is a problem associated with turning
green wood. It will vary from one type of wood to
the next. Typically, fruitwoods tend to distort
more than others. It also varies with the time of
year the tree was cut and how the logs are
stored.
Tools for Bowl Turning
The deep fluted bowl gouge is the most
essential and versatile tool for most bowl and
plate turning. The bowl gouge is heavier and
easier to control than other types of gouges. It
also allows removal of wood much faster and
with less vibration than other gouges. Most
average sized bowl work can be accomplished
with a 3/8" or 1/2" bowl gouge. A 1/4" bowl
gouge is best suited for smaller bowls and light
finishing cuts. Larger 3/4" and 1" bowl gouges
are only used for extremely large pieces.
Large domed scrapers can also be used to help
clean up the interior surfaces of bowls. A light
touch with the scraper slightly tilted will eliminate
some of the ridges occasionally left by an
inexperienced bowl gouge.
Bowl Turning Techniques
To Shape Outside of Bowl
1. Odd shaped burls, crotches and other
irregular shaped blanks require special
preparation before mounting in a chuck or
onto a faceplate. Remove the bark, if there
is any, from what appears to be the center of
the top of the workpiece.
2. Drive spur center into the top of the
workpiece with a mallet or dead blow
hammer.
3. Slip the spur center into the headstock taper
and bring the tailstock with a live or ball
bearing center into position. Lock the
tailstock to the bed and advance the
tailstock spindle in order to seat the cup
center into the workpiece. Tighten the ram
locking handle.
4. Turn workpiece by hand to ensure proper
clearance.
5. Start lathe at lowest speed and bring it up to
the maximum safe speed for the size of
work to be turned (see page 30). If the
machine starts to vibrate, lower the speed
until vibration stops.
6. Rough out the outside of the bowl with the
1/2" deep fluted bowl gouge, holding the
handle of the tool firmly against your hip. For
best control, use your whole body to move
the gouge through the workpiece.
7. As the bowl takes shape, work on the
bottom (tailstock end) to accomodate
attaching a face plate.
8. Turn a short tenon (about 1/8" long) the size
of the hole in the faceplate. See Figure 38.
This will allow centering the workpiece when
the faceplate is attached.
Figure 38
9. (NOTE: If you plan to use a chuck, turn a
tenon of the appropriate length and diameter
to fit your chuck.)
10. Stop the lathe, remove workpiece and attach
face plate or chuck (see "Mounting Stock"
on page 25).
The surfaces of faceplate and
workpiece should mount flush to each other.
11. Finish turning the outside of bowl with 1/2"
or 3/8" bowl gouge. Leave additional
material at base of bowl for support while
turning interior. This will be removed later.
To Shape Interior of Bowl
1. Stop the lathe and move tailstock away.
(You may want to remove the center from
the tailstock to avoid bumping it with your
elbow.)
2. Adjust tool support in front of the bowl just
below centerline, at a right angle to the lathe
ways.
3. Rotate workpiece by hand to check
clearance.
4. Face off top of bowl by making a light
shearing cut across the top of workpiece,
from rim to center.