Craftsman 351.21 7170 Manual De Instrucciones página 18

Another method of turning a ring makes use of a recessed
chuck.
• The work stock is mounted on a screw center and one half of
the ring is formed, but the ring is not cut away from its center.
• The stock is then removed, and a recessed chuck - mounted
on the large faceplate - is prepared to receive the ring in a
tight press fit.
• After being chucked, the remaining face of the ring can be
turned to the proper contour, thus cutting away the center
portion.
• In work of this type, take constant measurements or, better
yet, use a template to guard against over or under cutting.
Figure 62 1 2 3 4
TURNING BALLS
• Wooden balls of large size are first roughly turned between
centers, using standard procedures.
• Smaller balls can be mounted as faceplates on the small
faceplate or screw center.
• Lines drawn to indicate the center and ends of the ball
shape are helpful in plotting the curve.
• A template should always be used for accurate visual
observation of the work progress.
Figure 63
If the ball is mounted as a faceplate turning, almost the entire
surface can be turned before it becomes necessary to rechuck it.
• Rechucking can be be accomplished in a deep cup chuck
which will hold the finished portion of the ball in a tight press fit.
Another method of rechucking is to use a shallow cup chuck
which will not support the ball alone, but must be used in con-
junction with the tailstock.
• When using the shallow chuck, a wood block is fitted to the
tailstock so that the ball can revolve upon it. This block
should be lubricated with beeswax or grease.
• In using the shallow chuck method, the ball is constantly
shifted - never more than '/8 turn - and always in a definite
pattern.
Woodblock
re Oen er
B.B. _
Deep Cup Chuck Tailstock 1 \
Center Shallow Bearing Center
Figure 64
Since turning between centers makes the work a perfect
sphere across the grain, the ball must be mounted in the
chuck so that the first scraping cuts will round it up in the
opposite direction.
TURNED BOXES
Turned boxes involve deep recessing together with a special sys-
tem of working the lid and body of the box together as one unit.
• The inside of the lid is turned first.
• Next, the inside of the body is turned. A careful check must
be made when turning the lip of the body portion so that
the lid will be a tight press fit.
• The lid is then pressed onto the body and the outer circumfer-
ence and face of the lid, together with the outer circumference
of the body, are turned all at one time. This insures accurate
matching of the two pieces.
• After the work is complete, the tight fit of the lid can be
relieved by sanding the lip of the body.
Li_
Backing Block
Face Pl_t__
_
Figure 65
SEGMENTED TURNINGS
Segmented bowls and boxes are exceptionally attractive - and
this method of preparing wood stock is more economical than
the use of a large piece of stock. For some types of work, seg-
menting is the only practical method because a block (if obtain-
able) would be so large that it would be very likely to warp.
• The bowl illustrated in Figure 66 requires 12 segment pieces
for the sides. Bowls can also be worked with 6 or 8 pieces.
• To make the 12-piece bowl, a board about '/8x 3 x 30" is
cut into pieces about 2'/2" long, the saw blade being tilted
15 ° and the board being turned alternately face up and
face down to make the successive cuts.
• These 12 pieces are glued together and clamped by wrap-
ping the assembly with wire (or equivalent).
• When dry, the rim thus formed is glued to a temporary cir-
cular backing which is mounted on a large faceplate.
18
Figure 66
• A 3/4"deep recess of the largest possible diameter is
turned in the open end of the rim.
• The rim is removed from the lathe and stock for the bottom
is mounted in its place on a second faceplate. This is
turned to size - and a rim about _/8" deep is turned to
exactly fit the recess prepared in the rim.
• The rim is then fitted over the bottom and glued, making a
drum shape with a faceplate at each end.