Turn a Saueracker Shell
Turning Project: This is one of those turning projects that looks much harder than it is. With a little patience, you, and the finished piece, can come out looking pretty smart.
I was looking through Google images and came across a picture that captivated me. It was called a Saueracker shell. As I researched it further, I came across its origin. JEH Saueracker was a German ornamental turner working in Nuremberg in the early 1900s. I have not been able to get any more information on his work other than what is published in Mike Darlow’s Woodturning Methods. I just had to try it.
I used 2″ thick material, but it’s possible to use thinner stock. The size of the finished shell depends on the diameter that can be turned on your lathe. Inboard I can turn a 16″ diameter backer, which results in about a 9″ shell, the flutes of which turn in a clockwise direction. Outboard on my lathe I can turn up to a 24″ backer, which results in a shell about 14″, the flutes of which turn in a counter- clockwise direction. These pictures show you how I made the larger shell, but the directions are the same no matter what size you are turning, inboard or outboard. I used a 12″ face-plate to mount the assembly on, but you could adopt the technique to your favourite chucking method.
I chose to use the same wood for the shell and the crescent so that they could be used as companion pieces. If you have no use for the crescent part, you can use any scrap wood of the same depth and throw it away later. If the scrap crescent is less dense than the shell, you may have to use some counterbalances to even out the balance of the assembly in order to turn it smoothly.
Chemerika glued 3/4" thick plywood to the back of the workpiece, so there would be no screw holes in the finished piece. Paper, glued between the plywood and workpiece allows the two to be easily separated afterwards.
Lay Out the Shell
The circles for the backer and the shell are now laid out. Notice that the distance from the center of the backer to the close edge of the shell determines how large the center ‘eye’ is.
Once you have the inner circle drawn on the shell backer, and the marks drawn about 1-1/4" apart you can connect the center of the shell with each of these marks to create the different index marks. These marks only need to be on half of the shell blank.
Extend the Index Marks
Use a square to extend the index marks to the side of the shell blank.
Mount the Parts
The shell is placed back into the crescent moon with the #1 index mark centered on the crescent moon gap. It can now be secured to the faceplate. Hot-melt glue can be added to help secure the parts.
Mark the Eye
With the faceplate on the lathe you can spin the lathe by hand and locate the center point. Mark it with a dot, as seen here. With your writing utensil on the tool rest, and lined up with the outer edge of the shell circle, rotate the workpiece, creating the outline of the ‘eye’.
The first cut is made, and the ‘eye’ of the shell is shaped. Notice the outer edge of the eye ends at the outer edge of the shell.
With the ‘eye’ formed create a mirror cut on the opposite side of the eye’s edge, creating a even V-groove. Now that the first flute is complete you should sand it smooth.
The Second Flute
Once the shell has been rotated to the second index mark you can mark the second flute with white pencil crayon, and cut the second flute.
At this point about half of the flutes are done, and the shell is starting to take shape.
Chemerika used a few counter-weights on the back of the shell to account for the wood that has been removed from the shell.
Shape the Edge
You can either leave the perimeter of the shell round or highlight each section of the shell by removing some material with the bandsaw. If chipping is bad, removing material will go a long way to cleaning things up.
With one last flute to be cut the end is near. You can see the final white line on the upper, right side of the workpiece, which will guide Chemerika during the last cut.
Glue up a blank
A past purchase from a fellow CW&HI forum member (delivered by another forum member) had rewarded me with some 2″ bloodwood. I glued it into a 24″ square, 2″ thick panel. Then I glued on a 3/4″ plywood waste piece, with paper in between, so I would not have any screw holes directly into my bloodwood.
The 24″ circle is laid out with the 14″ circle that will become the shell, within it, nearly touching the outside circle. You want to leave enough room where the circles almost meet to be able to turn the whole assembly round and balanced on the lathe without cutting into your shell – between 1/8″ and 1/4″ is good. Next, cut out both of the circles, trying to stick to your lines as accurately as possible. The gap in the crescent can have its edges cut so it is about 1″ wide, making it easy to center your indexing mark.
The shell must be able to rotate within the larger crescent-shaped piece. If you can’t turn it, sand it until you can. You want the smallest gap possible between the shell and the crescent moon, as the bigger the gap, the more the wood will chip while you’re turning.
On the plywood back of your shell, lay out a circle with a radius 3/4″–1″ smaller than the shell. Now use dividers to mark equal distances around the circumference of the circle about 1-1/4″ apart. Mark them off in a counter clockwise direction from the #1 index mark for outboard turning (clockwise for inboard turning). These indexing points determine how far you will rotate your shell for each new flute you turn. Wider indexing points will produce fewer, larger flutes, and vice versa.
Draw a line from the center of your shell to the outside edge, through each of the indexing points, then continue these lines down the edge of the shell blank. It helps if you number them to remember where you are. The #1 index mark will be exactly opposite the eye of your shell, so take that into consideration if you want the grain to run in a certain direction.
Attach the work-pieces
Place the shell back into the crescent moon and center the #1 index mark in the gap of the crescent moon. Center your lathe faceplate on the plywood side of your assembly and screw the faceplate on with all of the screw holes used into the crescent moon and the shell, keeping the indexing mark centered in the gap of the crescent moon. I filled any gaps on the back of the plywood assembly between the shell and the crescent moon with hot glue so that centrifugal force does not move the shell towards the gap.
Mount the faceplate on your lathe and turn on the lathe at your lowest speed. Cut the outer edge of the assembly round so it will run as smoothly as possible. To mark the eye on the face of the shell, turn the lathe off and rotate the assembly by hand.
Mark the eye at the inner part of the shell, with the circle running completely on the shell, but touching the outside edge of the shell. The radius of the eye will be determined by the distance the outside edge of the eye is from the center point of your 24″ assembly.
When you turn the lathe on, you can start to shape the eye’s interior. I used a skew in a scraping position for all of the cuts. You can also shape the eye’s exterior by making a rounded V-shaped cut. Turn the lathe off from time to time to check that you have the deepest part of the V still centered on the outside edge of the shell. When you’re happy with the size and depth of both the inside and outside cut of the eye, you’re ready to move onto the next flute. You will not be able to go back to this point easily, so sand this entire V-groove now.
To move to the next flute, you will have to take the assembly off the lathe, unscrew the shell portion from of the faceplate, and align the next indexing mark. I used hot glue to help the shell portion stay in place when mounting it on the lathe, so I used a jigsaw to cut between the shell and the crescent, in order to detach the shell from the crescent. Center the next indexing mark in the gap of the crescent, remount it to the faceplate then add some hot glue.
To mark the next flute, with the lathe turned off, put your pencil on the lower-right edge of the eye and turn the lathe by hand, keeping the pencil on the same spot on the tool rest. This will show you the path your tool will cut for the next flute. Turn the lathe on and make the rounded V-groove.
Continue to rotate the blank, mark out each new flute and create the V-groove this way. You can try to start each flute in exactly the same position, but I found this was quite difficult. I chose to try to end the cut for each flute in equal increments to the right side of the eye. As you look through the photos of the different shells, you will see that no two are the same, as far as where the flutes start. I don’t think it really matters so long as they look pleasing to your eye.
The counter-balances are added as needed to keep the lathe running as smoothly as possible. They need to be moved and adjusted as you change the position of the shell and take away some of the weight. I just screwed scrap pieces as needed onto the plywood back. By loosening the belt from the motor, the assembly tends to rotate until its heaviest point is down. If the counter-balances are close to the right spots, the assembly will not drift from any place you turn it. Make sure the counter-balances will not come into contact with any of your lathe. Give the lathe a test spin by hand before turning it on.
Continue to cut each flute and turn the shell until you have reached the last flute on the outside edge of the shell. Dismount the assembly from the lathe, remove the faceplate and separate the shell from the crescent for the last time. Remove the plywood backer from each piece.
Shape the edges
You can further shape the ends of the flutes with the bandsaw, or leave the shell perfectly round. If you had problems with the outside edge of the shell chipping, shaping will cut most of the chipping off. Sand and finish the piece. There is a lot of end grain in the finished piece. The more time you take to properly sand it, and apply the finish, the nicer your finished shell and crescent are.
So now you’re asking yourself, “what is it?” The shell and crescent can be a very striking wall accent. The shell could also be the lid of a box, or an appliqué or inlay on a piece of furniture. Maybe it is just a challenge that you can be proud of completing.
What would you do with this shell? Share your ideas on our website, in the comments section below this article.