Twice-Turned Bowl Turning 14.Jun.17
1. Cut log slightly longer than its maximum diameter. NOTE: The sooner you start on the
first turning after the tree is cut, the better.
2. Cut log in half lengthwise, having regard to the symmetry of each half and the position of
any knots or other significant features.
3. Trim half log to circular shape using band saw if possible or chain saw if too big.
4. Mount blank to lathe between centres, flat side at head end. Check for reasonably true
running and adjust if necessary before final tightening of tailstock. For larger blanks you
may consider using a screw chuck or faceplate.
5. Turn outside of bowl. Cut tenon or recess to reverse mount in 4-jaw chuck. (Generally
prefer recess with larger diameters.)
6. Reverse blank and mount in chuck by tenon or recess. (Make sure centre of base is
marked for later reference.)
7. Turn inside of bowl to wall thickness about 10% of max diameter. Try to keep wall
thickness fairly uniform to prevent stresses from uneven drying. Don’t worry about
achieving a nice finish. For large sizes and/or premium wood, coring can be done to
create more bowls and save on shavings production.
8. Coat outside of rough-turned bowls with anchorseal, or boil, cool and bag. Leave to dry
for appropriate time. (1 year/inch of thickness.)
1. Select dried rough-turned bowl from First Turning or Coring. If cored, you may need to
estimate the centre point on the base. Make dimple with bradawl. NOTE: It is useful to
measure the thickness at the centre of the base before mounting on the lathe.
Expand 4 jaw chuck to maximum. Hold inside of bowl over chuck jaws while bringing
up the tailstock live centre to engage the centre point. (Penetration of the live centre can
be limited by means of a washer or nut placed over the point.) Ensure that all 4 jaws
contact the wood by adjusting the contact points and tightening the tailstock as necessary.
2. As the rough-turned bowl dries, it becomes oval in shape. This is the reason why we
leave a fairly thick wall in the first turning so that we can turn away the outside on the
long axis and the inside on the short axis and still end up with a circular bowl. The
uneven shape will cause a lot of vibration when rotating. The larger the bowl, the more
troublesome this vibration will be. True up the rim first, and then turn outside of bowl to
finished shape. Use shear scrape technique to get as fine a finish as possible to minimize
sanding time. Do not sand the outside yet. If stub left from coring is too small, turn it
away and cut new tenon to suit chuck. (This is where it is useful to know the thickness of
the base – how much wood you have to work with.)
3. Reverse the blank and hold in the chuck by means of the tenon or recess.
4. Turn the inside. After removing the excess out-of-balance material from the inside, you
may be able to take another light cut on the outside to reduce vibration still more. Now
that the bowl is round you can increase the speed and continue hollowing the inside of the
bowl to the desired thickness. The conventional method of cutting using the bowl gouge
starts at the rim and proceeds towards the centre, riding the bevel and with the flute
towards the centre so that the cutting edge to the left of the tip does the cutting. With dry
wood you will find that you cannot take as large a shaving as you can with green wood in
the first turning. Take light cuts when approaching final thickness and try to minimize
chatter and tearout. Ideally, the final cut should be made with a single continuous sweep
with the bowl gouge. Don’t despair if you have difficulty with this at first. A round-nose
scraper can be used to get an excellent finish on the bottom third of the inside of the
bowl. This also solves the problem of riding the bevel all the way to the bottom. Turn the
lathe off and run your fingers across the bottom of the bowl to check for ridges. Use a
pencil to mark high spots and remove them with the scraper. Fingers are also the best
way to check for consistent wall thickness in small bowls. For larger bowls you will
need callipers. Don’t try to check wall thickness while the lathe is running. The bowl
rim is like a circular saw!
4a. As bowl size increases and wall thickness decreases, it becomes increasingly difficult to
achieve a good finish cut on the inside, as the tendency to flutter increases. There are two
spots on opposite sides of the bowl where it is difficult to control grain tearout. (You will
soon discover where these are!) I have developed two techniques to help solve this
problem: - The first is to use a pull cut with the flute facing towards you and cutting with
the left side of the flute. Once you have found the appropriate angle of presentation of
the gouge to the wood, try to maintain that geometry as the cut progresses from centre to
rim. The second way to control flutter is by using a bowl steady. I have found that the
commercially available types using wheels riding on the outside of the bowl create more
problems than they solve. The method I advocate involves mounting a disc of wood on
the live centre of the tailstock and running it in to bear against the inside of the bowl.
You can then use the pull-cut technique from the disc contact to the rim. With large
diameter bowls, a number of progressively smaller discs can be used and the finishing
cuts done in stages and blended appropriately.
5. When you have done the best you can with the tools, sand the inside. If your lathe is
reversible, you will find it beneficial to sand in both directions. Resist the urge to sand
the outside at this time. Wetting the wood occasionally will raise the grain and allow you
to achieve a better finish. There are always two spots on opposite sides of the inside of a
bowl where it is almost impossible to avoid some degree of tearout. Some dedicated
hand sanding with 80 grit on these spots may help to reduce the total sanding effort.
N.B. When sanding, be sure to clean the sanding dust away between each change of grit.
A vacuum or compressed air blower is handy for this. Pay particular attention to any
knots or bark inclusions which may have small pits where grit particles can lodge, to be
released later when you have progressed to finer grits.
6. When satisfied with the sanding job, you can apply the finish to the inside of the bowl if
it is one of the finishes that can be applied and buffed immediately. (Shellawax or
Clapham’s Salad Bowl Finish.) For other finishes that require time to cure, leave the
application of finish till later.
7. Remove from lathe. Measure thickness at centre of base with callipers before
remounting. Use a cushioning block in the chuck, and a pad to protect the finished inside
of the bowl before placing bowl over the chuck. Bring up the tailstock to the centre of
the base and snug up tailstock.
8. Finish turn the base to as close as you can get to the tailstock centre. Use the thickness
measured in 15 above and the height of the stub at the centre to determine how deep to
make the recess in the base. Turn a foot if the design calls for it or blend in the bowl
outside curve all the way to the bottom. Make any finishing touches to the outside
surface with the side of the bowl gouge used in the shear scraping mode.
9. Sand the outside of the bowl and the accessible part of the base. (Use a flat sanding
block with the coarser grits to maintain a flat plane surface on the foot. When sanding
with a block, keep it moving to avoid burning the paper.)
10. Apply finish if it was done on the inside.
11. Remove from lathe, sand off stub, sign and finish base.
Keith R. Notley
Notes of KWT Club Meeting of May 10, 2017 held at Frontenac High School.
· Nelson called the meeting to order at 1855.
· Herb discussed the Joint KWT-KWA symposium to be held at the Communications Museum of June 10.
o Objectives of the Gallery is to show the public the work KWA and KWT members do and to raise the profile of our respective clubs
o Show to be called “Artistry in Wood 2017”
o Registration for the event is free to KWT members but the organizers need to know you’re coming. Therefore, there will be a registration. Registration forms were available at the meeting. The registration form will also be posted on the KWT Website.
o A brief description of items should be included with the registration. The “item size” part of the form is not really applicable to KWT. It is geared toward KWA, some of whom could be bringing in large furniture items.
o Entry of items will be open to KWT and KWA members (only) and items will not be screened / juried.
o Members were strongly encouraged to submit at least one item. Organizers are looking for a broad spectrum of work from turners of all experience levels.
o If you are unable to attend, please leave a piece or 2 with someone to take on your behalf
o Tables are 6 ft in length.
o The room is available for set-up from 1300 – 1600 on Friday
o Small posters are available. Please take 1 or 2 to post in local businesses
o There will not be an entry fee to members to display / sell items or a club commission on sold items.
o Sale of items will strictly between exhibitor and buyer
o In order to encourage attendance, entry will be free to the public
o Exhibitors must bring their own extension cords if they need them
· Malcom Zander from the Ottawa Valley Woodturners made a presentation and demo of turning thin walled pierced vases. See also Malcolm’s handout (available on KWT website at http://kingstonwoodturners.com/meeting-notes-2017/).
o No sophisticated tools are required.
o A 60o bowl gouge is used for 95% of the time, with a 45o bowl gouge also used
o Endgrain and cross-grain examples were presented
o Why thin-walled?
§ Create a form with lightness and delicacy
§ If the item is pierced, a thicker wall “closes off” the holes when viewed from obligue angles.
o Why use dry wood?
§ Dry wood moves much less during turning
§ Gives more time to the turner to cut the thin wall without the piece becoming oval during turning
§ The piece can be sanded to its final finish on the lathe
o Why use cross-grain blanks?
§ No special tools are required, just bowl gouges
o Malcolm’s current work evolved from starting with natural edge bowls with sapwood rims
o Most lace is based on a hexagon shape
o The “Heart” bowls are turned end grain
o One idea can lead to a whole series. For example, the natural edge with leaf motif
o For a natural edge piece, the high wings must be the same height. It is aesthetically ok if the low wings (ie front and back of bowl) are of different heights.
o Use the tailstock for support for as long as possible
o The cone center can be effectively used during hollowing
o Once the wall thickness is about ⅜” thick, switch to the longer bevel (45o) bowl gouge
o To create an even, thin wall sight along the profile using both eyes.
o Calipers can also be used. Set the calipers so there is a gap at the desired thickness. As you progress down the bowl if the gap lessens, the wall is too thick.
o When entering a cut near the edge, use your left thumb as a steady/fulcrum to prevent the gouge from “skating” toward the rim
o Work in 1” increments so that the piece does not become prone to flexing during turning
o Once you are done a section, you can’t go back.
o When hollowing, set the tool rest to be parallel to the profile.
o The bowl in the presentation was approximately 12” diameter with 1 mm wall thickness and sanded to 2000.
o Piercing can be done with a dental drill or an NSK unit.
o Both turn at approximately 400 000 rpm.
o The NSK is a “pen” configuration, while the dentist’s drill is a right-angle configuration
o The NSK has enough torque to handle a wall thickness of ⅛”.
o A dental drill can go up to about 1.5 mm (1/16”)
o A 40 000 rpm unit, such as Foredom, tends to track the grain
o Cut with the bit perpendicular to the surface of the piece
o Use one finger as a fulcrum for steadiness.
o File the holes with a diamond file to smooth them and to get rid of burn marks.
o Prior to filing, most of the burn marks can be removed by “wiping” the cut surface with the edge of the NGK (or dentist’s drill).
o The Rollie Munro “Holy Rollie” hollowing tool was demonstrated and discussed.
o Good light is essential for thin walled vessels and for piercing
· Several items were presented at Challenge / Show and Tell including:
o Box incorporating alumilite resin
Malcom has provided us with a PDF hand out from the demo he did for us .