Lathe
Turning Tips
Practice, sharp tools, and a reliable machine - these are the surest
avenues to beautiful lathe turning results. And here are several
tips, hints, and helpful workshop methods that will ease you into
more professional-looking lathe projects.
What
kind of stock is best?
For the beginner, the textbooks are right: stick with clear, straight-grained
wood, free of checks, knots, and other defects. Also, stock of a
consistent density throughout is preferred. To get to know the "feel"
of your lathe, practice turning white pine or poplar.
Finding
centers
There's more than one way to find exact centers. One sure-fire way
is to buy a product made to find centers: a plastic center finder,
center-finding rule, or a Bulls-Eye TM. The old-fashioned method
is to use a straightedge, pencil, or awl and draw diagonals across
opposite corners on each end of the stock.
Find the center of irregular stock by marking a right triangle and
dividing the hypotenuse in half. Another way of finding the center
of irregular stock is by using a center finder (Part #731195). I
have found this to be one of the easiest and quickest ways to accomplish
this.
On
really odd-shaped stock (the kind you're apt to find in a woodpile),
lay a square on the end of the piece, and mark the three points
where the square touches the edges. Draw lines between these points
to form a right triangle. Next, divide the length of the hypotenuse
(the side of the triangle opposite the right angle) in half. That
halfway point is as close as you'll get to the center of the stock
Seating
spur and cup centers
If you've ever had a perfect piece of cherry or oak split as you
seat the drive center, read on. Next time, try sharpening the end
edges of the spur, or use a handsaw to cut kerfs corner-to-corner
in the end of the stock. The spurs will seat in the kerfs.
To
keep the cup center from burning as the turning wood builds friction,
apply wax or soap to the cup and point. Or, avoid burning the end
stock by using a live center (Part #505602); its sealed bearings
rotate with the work so there's no friction between the cup and
the stock.
Note: MARK V accessories include both a standard cup center
and a drive center. Which the standard may scar the very end of
the stock, it allows full use of the MARK V's 34" lathe bed. Using
the live cup center reduces the maximum length of stock.
After
"setting" the drive center (use a soft-faced mallet), mark the stock
in relation to the setscrew in the drive center. That way, if you
must remove stock from the lathe and remount it later, you can easily
line up the center so the spurs seat in their original position.
Marking your bowls isn't necessary. The screw holes in the MARK
V faceplate are positioned irregularly so that stock can be mounted
and remounted in the same position. Do attach the faceplate so that
no two screws run parallel with the grain of the stock.
The
most common way to attach stock to the faceplate leaves undesirable
holes in the bottom of your project. Here's how to avoid the holes:
glue a scrap mounting block to the stock you want to turn with one
sheet of newspaper in between them. After turning, split the paper
joint, and you'll have a clean, even separation.
Tip:
Use a Bandsaw to round-cut faceplate stock before mounting stock
on the lathe - roughing the stock with the Roundnose will be safer
and easier.
Roughing
spindles
Rough-cuts should be turned at slow speeds; too fast and the stock
might vibrate off the lathe.
Use
a gouge to bring stock into round. Rest the back of the tool's shank
on the turning stock to test for roundness. If the gouge doesn't
vibrate, the stock is cylindrical. Avoid turning too small a diameter
when roughing. Simply scribe pencil lines along the sides of the
rough stock. When the dark blur of the lines disappears, the stock
is round, as large a diameter as possible.
Turning
bowls
A common misconception is that wooden bowls are turned from the
heart of trees - and that looking down into their center, the annual
rings should splay outward in concentric circles, as the sawed-off
trunk of the tree would look. Bowls turned in this manner will probably
spit, crack and warp. Fine wooden bowls are generally turned with
the grain running lengthwise, from stock taken from the outside
edges of large trees, with the grain running across the bowl. To
see the annual rings, you'd look at one side of the bowl rather
than the center.
Turning
contours
Once roughing is complete, increase the lathe speed, but not above
"L" on the MARK V. Before your next cut, stop and think ahead.
Plan
the design you want and lay it out on paper. Use your plan (and
a pencil), mark dimensions on the stock. Next, use a parting tool
to make dimension cuts to within 1/16" of the final diameter. Use
a set of outside calipers to check the diameter of
the cut.
To
cut the inside of a bowl to within it's final depth, drill a depth
control hole in the center of the stock. If possible, use a brad-point
bit - it leaves a flat bottom hole and won't drift. Then scrape
the remainder of the bowl bottom to this depth. Refer to your owners
manual or call Shopsmith Technical Support for instruction on how
to the Tailstock Chuck Arbor (Part #505603).
Always
work "downhill" - turn larger diameters first, work from top to
bottom of the bead, and the outside of the bowl to the center. This
helps eliminate chatter that develops in long slender turnings.
Don't let your chisel move off the tool rest; keeping the tool rest
centered at the area being cut solves this problem. Since the tool
rest is the fulcrum for your chisel, keep it within 1/8" of the
stock, even if it means extending one end inside a bowl. When scraping,
place the rest near the centerline of the diameter of the turning
stock. For shearing, raise the rest to where you feel most comfortable.
A good rule of thumb in shearing is to raise the toolrest slightly
above the centerline of the stock.
Using
the right tool
In general, you should select the lathe tool that works best for
you. Time-honored guidelines say that a gouge and Roundnose are
commonly used to cut flat and convex surfaces, such as taper and
beads on spindles. When turning bowls, use a bowl turning gouge.
Ask us about some recommendations.
Don't
hold the tip of a skew in the wood more than an instant - push it
in and get it out. Otherwise, the chisel can heat up, burn, and
draw out the temper.
Feed
your tools slowly and steadily; never jab or force a tool into the
wood. If your chisel begins to chatter or you get a rough cut, check
the sharpness of the edge. If the sharpness is good, then the stock
may be turning too fast or maybe you're trying to remove too much
stock at one time, or perhaps the stock is whipping because it's
become too slender to turn without some sort of center rest.
Sanding
and finishing on the lathe
-
When
sanding on the lathe, Always remove the tool rest from the
lathe. Protect the way tubes on your MARK V by using a scrap
board, cloth, or aluminum sheet stock formed to fit the tubes.
-
Don't
use new sandpaper to finishsand your work; its sharp grit can
leave rings on the wood. Before using new sandpaper, rub it
together. Rather than holding sandpaper still, move it back
and forth on the turning piece perpendicular to the rotation
of the piece.
-
To
sand coves and tapers, cut a narrow strip of sandpaper and strengthen
its back wit a piece of transparent or plastic electrical tape.
Held taut, this strip will reach down into tight coves and beads.
-
For
long tapers or flat surfaces, use a sanding block. Or fold sandpaper
in thirds and place steel wool or felt between the sandpaper
and your fingers (to protect your fingers from friction heat).
-
Reduce
sanding time by first fillig major tears in the wood. If you're
sanding faceplate work, mount the piece on the upper auxiliary
spindle of the MARK V. This reverses the faceplate direction
and you'll be sanding against the direction the piece was turned.
-
Before
applying finish to straight, tapered, or gradual contours, stop
the lathe, and use fine grit sandpaper to lightly finish sand
with the grain.
-
Finishing
on the lathe allows you to apply a quick and even finish. For
best results with oil finishes, apply it both to the wood and
the sandpaper. While the piece turns, the sawdust will mix with
the finish, sealing the pores of the wood. Follow the same way
tube protection as with lathe sanding.
-
If
you plan to stain your work, remember that over polishing the
wood with tools or extra-fine sandpaper will close the wood's
pores. Pine is most susceptible to over polishing, to the point
that resin is drawn out and prevents stain from soaking into
pores.
Scraping
vs. Shearing
Another of woodworking's hotly contested questions: Which is best,
scraping or shearing? Once again, it's something you'll have to
decide for yourself, but here are a few facts:
Scraping
is newer. It started in the pattern-making trade and is now popular
among hobbyists and other amateurs. Still, most pros use the technique
at certain stages in their projects. This method removes stock slower
than shearing. You can count on more accuracy because it's easier
to control the amount of stock you remove. Scraping is quicker and
easier to learn, but leaves a rougher surface and requires more
sanding.
Shearing
has been the accepted method for generations. Fathers passed the
technique on to sons, and in this way, the method was perfected
in the old trade. Shearing removes wood rapidly and leaves a surface
needing very little sanding. But shearing is time consuming and
takes patience and practice to learn.
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