"Ask any one hundred turners how to
do something and you will get at least 99 different answers" Anon.
article below is how I turn one-piece hollow forms. This is not anyway
definitive but merely how I have found to turn more efficiently.
THREE PHASE STEP-BY-STEP PROCESS
Phase 1-Rough Turning A Side-Grain
1. With a chain saw, cut a green log the
length equal to the diameter of the log and then cut it down the middle.
Removing 1inch beyond the pith, if you are not going to turn it immediately. If
you are not going to turn it immediately paint the ends with some type of end
sealer or latex paint to reduce checking. [Notice, if you are going to process
the logs for later turning, cut the log 2 inches longer than the diameter of the
log, split the log removing 1 inch either side of the pith and coat the ends
with end sealer]
2. Determine the grain orientation on the blank. If it is to be a natural bark
edge hollow form, the top of the form will be at the bark side and the bottom of
the form is toward the pith.
3. To rough out the hollow form blank- Draw a circle on the bottom of the blank
to determine the diameter of the bowl. Matching the size with a plywood disk,
which is mounted and centered on the bark side of the blank. Place the blank on
a band saw with the pith side on the band saw table and cut around the disk. Or
rough it out using a chain saw.
4. Mount the rounded rough blank between centers with the bark edge at the
headstock and the pith end at the tailstock. Make sure it clears the lathe bed
and tool rest by manual turning the blank 360 degrees. Visually re-arrange the
headstock and tail stock positions until at least the high sides are equal and
if possible the lower sides also. At least two of the sides should be in the
same plane for a balanced design.
5. Rough out the shape of the hollow form between centers, using the tailstock
for safety, at a low lathe speed. Since the form is turned green, it will warp
as it dries, so only the rough shape is needed at this stage. It is important at
this stage to get the design of the form correct and accurate. NOTE-After the
interior is removed, it is almost impossible to change the design.
The largest part of the hollow form should be in the top or bottom 1/3 of the
form not in the center.
6. Using a rough out gouge or a 5/8 inch bowl gouge held at approximately 30
degrees up from horizontal, present the bevel until it rides the blank and raise
the handle to pivot the cutting edge into the work and sweep the tool through an
arc until it begins to cut. The flute of the tool will lie about at 45 degrees
of vertical. The bevel does not have to ride the piece at this point. Rough
out from the bark edge to the base or you will knock off the bark when turning
it. Roughing speed on the lathe should be at a low speed, about 500-800
RPM's. Stop the lathe frequently to check your progress and to move the
tool rest closer to the blank. Always make sure you are supporting the cutting
edge. (Take care that you never present an unsupported edge of a tool
to the wood, you will get a catch.) This is because when there is no support
beneath the edge of the tool, the downward force of the rotating wood snaps the
7. Refine the design of the hollow form when it is in balance at a higher speed
900-1000 RPM's, using a more sensitive cut (sheer cut). Apply thin layer super
glue to the bark edges after the hollow form profile is completely established,
if it is to have a bark edge.
8. Prepare the base of the blank to be fitted with a faceplate or a chuck. If
the form is very shallow, you can glue a scrap block onto the bottom with Yellow
glue or Polyurethane glue (it works best because it needs moisture for it to
cure). Let the glued blank dry over night, placing it in a bag or sealing the
outside with end sealer better to do both. Failure to protect from drying will
cause cracking. It is a shame to put all of this effort into a piece and have it
crack because of carelessness.
9. Mount the blank on the faceplate or chuck to remove the interior of the form
You are now ready to rough turn the interior of the form. This is the hardest
part of this exercise since you will be "turning blindly inside the
form". You can drill a 1 inch hole in the center of the form to a depth of
1 inch from the bottom of the form blank or use a boring bar to make this cut.
This provides a depth measure when removing the center of the form.
10. Check the form blank is running true before turning the lathe on. Now
is the time to get it running true by re-turning the sides of the form, if
necessary. Keep the tailstock against the form blank for safety. When it is
running smooth, you can remove the tailstock.
11. Interior hollow turning- Rough out the inside of the form to about 1 inch
thickness. Starting with the inside of the hollow form (where the depth hole is)
continue to remove the interior in a scooping motion using the body to support
the tool and moving in a dance-like motion around the bowl. This movement is
from right-to-left (from the lathe bed toward the head stock in a continuous
motion) after you have cleaned the interior all you can with a straight tool,
you then proceed to hollow with a curved tool as the interior of the form
becomes wider and deeper. Since you are hollowing the form through a narrow
opening, (This requires a steady hand! Go slow and remove the waste often
since accumulation will bind the tool causing it to rip from the chuck and
destroy the piece. This can be done with an air hose, by hand or using a coat
hanger as a "scraper").
12. When a uniform thickness of 1 inch is achieved. Remove the form from the
lathe and coat the interior edge of the bark with super glue. Coat both the
interior and exterior of the form with end sealer and place in a bag paper or
plastic on a shelf to air dry. Weigh the rough form and record the weight. Turn
the hollow form bag inside out and place the form back in the bag and record the
weight at least every two days. When the form no longer loses weight, it is
stabilized. It can be further dried in a microwave (this technique is for
another article). It should be at about 10-12 percent moisture content to finish
turning. Kiln dried lumber is 8-10 percent moisture. Average drying time is 90-
120 days depending on conditions and the type of wood. The same procedure can be
achieved with the use of a moisture meter.
Phase 2- Finish Turning
13. Remount the dried blank on the lathe. It will have warped so that the
faceplate will have to be remounted, re-chucked or re-stabilized. This can be
done between centers again by using a reverse chucking method. Finish turning
the outside of the form so that it runs true and refine the design. Finish
sanding the outside of the form on the lathe either by power sanding with a
drill or by manual holding the sand paper against the bowl as it spins. (MAKE
SURE YOU FOLLOW ALL SAFETY PRECAUTIONS FOR THIS TECHNIQUE.) Sand through the
grits starting at 100 through 400 grit. Coat the outside of the bowl with one
coat of DEFT semi-gloss lacquer. Let it set 3 minutes and wipe with a cloth.
Turn the lathe on and burnish with the cloth or with shavings. Make sure you
protect the lathe bed against splatter.
14. Finish turning the inside of the form from the edge to the center of the
bowl removing 1/8 to 1/4 inch at a time. Finish to 1/4" to 3/8" in
uniform thickness in the walls and a little thicker in the bottom. Sand the
interior and DEFT coat it like the outside of the bowl. Mark the interior bottom
of the form on the outside of the hollow form to indicate the interior's depth.
Remove form from the lathe. Remove the faceplate.
15. Repair any missing bark with the excess bark saved from the interior part of
the bowl. Attach it with thick super glue and accelerating spray.
16. Reverse chuck the finished form. (Mount a smaller form on the faceplate and
mount it on the headstock this is called a Jam chuck. Cover this form with a
piece of carpet pad or leather to prevent "burning" and to provide a
friction pad to drive the hollow form.) Place the neck of the hollow form
against the jam chuck and tighten the tailstock against the bottom of the form.
With the lathe at slow speed, make a concave impression on the bottom of the
form, making sure not to cut through or make the bottom too thin. The bottom of
the form before it is finished should be twice the thickness of the sidewalls
plus the length of the screws holding it to the faceplate. The bottom of the
form should be about the same thickness as the side walls when completed. For
example, if the wall thickness is 1/4" thick then the bottom before
finishing should be 1/2" thick. When it is finished turned and sanded it
should be about 1/4" thick. Sand with the same grits as the rest of the
form. Sign an date with a Sharpie pen. Coat the bottom lightly with spray Deft
lacquer. Let it dry 2 hrs.
Phase 3 -Finishing the Hollow Form
17. Coat the entire form with another coat of DEFT lacquer. Wipe dry after
15 minutes setup time, Let dry over night.
18. I use a jeweler's finish on my bowls and hollow forms. This is a technique
that uses buffing wheels and compounds to get the desired finish. This process
A. Tripoli wheel charged with red Tripoli is used to remove excess finish and to
smooth the outside of the form.
B. Coat the inside and outside of the form (anywhere you can reach) with a paste
wax that has high carnauba content. Let it set for 30 minutes and buff off with
the wax wheel charged with pure carnauba wax.