Powermatic 3520B - Manual (Page 22)

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For best results, use a slow speed grinder (1800
rpm) fitted with a 60-grit aluminum oxide wheel
(for shaping) and a 100-grit alum. oxide wheel
(for final sharpening and touchup). The grinder
should be located near your lathe and at a
comfortable height. A diamond dresser will keep
the wheels true and eliminate glazing.
Never allow the tool to rest in one place on the
wheel, keep it moving and use a light touch.
Carbon steel tools can overheat easily and
should be cooled frequently. If the edge turns
blue, it has lost its temper and should be ground
past the blue area. High-speed steel tools are
not as likely to overheat, but can be damaged if
allowed to get red hot. High-speed steel tools
should not be quenched for cooling. Honing with
a diamond lap or slipstone will save trips to the
grinder and keep the edge fresh.
Spindle Turning
Spindle turning takes place between the centers
of the lathe. It requires a spur or drive center in
the headstock and a live or dead center in the
tailstock. A cup center rather than a cone center
in the tailstock will often reduce the risk of
splitting the stock.
Figure 30 shows the basic profile shapes in
spindle turning.
Stock Selection
Stock for spindles should be straight grained
and free of checks, cracks, knots and other
defects. It should be cut 1/8" to 1/4" larger than
the finished diameter and may require additional
length so the ends can be removed later. Larger
stock should have the corners removed to
produce an octagon making the piece easier to
rough down to a cylinder.
1. With a combination square, or plastic center
finder for round stock, locate and mark
center on each end of the workpiece.
Accuracy is not critical on full rounds but
extremely important on stock where square
sections are to remain. Put a dimple in the
stock with an awl or nail, or use a spring-
loaded automatic center punch.
2. Extremely hard woods may require kerfs cut
into the ends of the stock (Figure 30) using
a band saw, so the wood will accept the
spur center and the live center.
3. Drive the spur center about 1/4” into the
workpiece, using a wood mallet or dead
blow hammer as shown in Figure 32. Be
careful that you do not split the workpiece.
Never use a steel face hammer and never
drive the workpiece onto the spur center
while it is mounted in the Lathe spindle.
Figure 30
Figure 31
Figure 32