Archive for January, 2006

Small Cherry Vessel

Wednesday, January 25th, 2006

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Finally managed to find a little time for turning. Went into the shop thinking about turning a bowl from some mystery wood, but figured I better warm up a bit first. A small leftover cherry block, that was supposed to become a box but a knot prevented that. Anyhow, this little whatever we should call it is all I got done today.

It is 3” in diameter and 2” tall, sanded through 600 grid and burnished with shavings. I am thinking of applying a few coats of the Polyurethane Gel, we’ll see. To turn the bottom I pressed it into a piece of scrap wood on my faceplate, it happened to have a grove that was almost perfect and needed just a little tuning.

Music

Grobschnitt: Sonnenflug Transatlantic: Stranger in my soul (live)

Addendum: I did add three coats of that Rockler Polyurethane Gel. Simply wiped on a thin layer with a piece of paper towel, then wiped it of with another piece of paper towel. No sanding. The results are very pleasing: a slight satin sheen, and it really highlights the iridescence found in that particular piece of cherry wood.

Segmented Turning

Tuesday, January 10th, 2006

The topic of todays MWA membership meeting was segmented turning. Jim Jacobs gave a very informative intro and demonstrated some of the home-made jigs he uses.

Here a quick summary:

For inspiration Jim looks to pottery and glass vessels. Once he has decided on a size and shape, he starts out by making a full-sized layout. From that he determines the thickness and diameter of your segmented rings. To get from the diameter of the rings to the size and angle of the segments, he uses these steps:

circumference = diameter * 3.14
divide circumference by number of segments
add 1/4" for waste

And for the angle:

cutting angle = 360° ÷ number of segments ÷ 2

Here is a small form to make those calculations (javascript required):

Number of segments: Diameter:

        Number of segments:   
                  Diameter:   
             Circumference:   
              Segment size:   
                 Cut angle:   

To cut the segments Jim recommends a Miter Saw with a fine-toothed blade and equipped with a home-built fence. That fence is essential, without it there is danger of kickback, the saw could gobble up and spit the smaller pieces.

Jim also uses a self-made sort of poker tool to hold down smaller segments during sawing and sanding. He made that tool from a brass rod. One end is ground into a point, and bend at a 90° angle approximately 3/4” from the point. The other end was fitted and glued into a small turned tool handle.

Once the segments are cut the ends need to be sanded to a precise angle, so that when fitted together the segments form a perfect ring with no gaps where the segments meet. To this end Jim built a disk sanding attachment for his lathe: an 8” round board is attached to a faceplate, and a self-stick 80 grid sandpaper disk is affixed. Then he built a sanding table with a sliding sort of miter gauge that can be set to precise angles required for the specific number of segments used in a ring. A special home-built push stick with a depth stop further makes this task easier.

The cut and sanded segments are glued together using regular woodworking glue. Simple band clamps clamp the pieces together until dry. Jim showed how multiple band clamps can be joined to make a larger clamp, a handy tip.

After the rings are glued up, the mating surfaces must be trued up in preparation to gluing the rings together. A large enough drum sander can be used if available. Alternatively Jim mounts the ring on an expanding chuck, using small spacer blocks if the ring is to large for the chuck. Then he trues up the surface with his bowl gauge, using a steel ruler to check for flatness.

To form the bottom a rabbet can be turned into the bottom-most ring. The bottom plate is then turned to fit the rabbet and glued into it, and a waste block glued to it later.

The rings need to be glued together one at a time. Another home-build jig makes this an easy task for Jim: He built a box from 3/4” plywood. That box is open to the front. In the bottom is a simply hydraulic jack that pushes a metal plate and a board slightly smaller than the box upwards. The sides of the box have 3/8” deep dadoes to receive a shelf in jut the right height. For glue-up the rings are clamped between the lower board that is pressed upwards by the jack, and a shelf in just the right dado slot. A very handy jig!

With the glue-up completed the entire structure can be mounted on the lathe using the waste block. For a more stability a plug can be turned to fit into the opening that is to be the top. With the plug in position the tail stock can be used to support the entire structure. Then it is turning and finishing as usual.

Maple Platter 2nd Edition

Tuesday, January 3rd, 2006

One of my first turnings was a Maple platter my wife had requested to put a large candle onto. Back then I knew even less what I was doing than today, so the thing was pretty roughly turned and unfinished. The other day my wife pulled it out again. Having since come to appreciate the beauty Maple can have (yes, this is another piece from the famous Firewood heap), I really thought this beautiful piece of wood deserved better.

So I chucked it up in my Longworth Chuck, cleaned it up a bit, and then buffed it with the Beall Buffing wheels. I really like to look at this piece of wood. It has some spalting, some quilting and even some curl in it.

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Minnesota Woodturners Association

Sunday, January 1st, 2006

I finally joined the Minnesota Woodturners Association. Given all the benefits the membership fee will pay more than for itself. Should have done that sooner!