Welcome to the Spiral Coffee table Instructable. I hope you will enjoy reading this Instructable as much as I did in creating it. I will also be providing all of the files and formulas used in the construction. Any customization of the table is welcome. Now, lets start off with the purpose and goals in making this project.
The purpose of this design is to make a visually appealing and structurally sound coffee table.
Several main goals existed in this project:
1) To illustrate the steps of starting conceptually from a conceptual idea appealing furniture.
2) To utilize CAD for precise dimensions and assembly fluidity.
3) Create tooling that was easy to use for repeatable results.
4) Compare a Virtual-created model to Physical result.
Power tools ,woodworking and stain/paints are used for this project, so please, use safety-glasses and gloves when appropriate.
Now comes the brainstorming the concept of the table.
Step 1: Conceptual Design and Equations
I started off on this project deciding on what would be a handsome table and was interesting from the top down-design. I choose the spiral design of the legs. I then had to support the structure, so I had designed each leg be supported by the previous, as well as an optional base for additional support.
Coming up with an initial design wasn't too hard. However making an appeasing twist and correct height involves some trigonometry. The major factor of this table was the side length. An easily measured length was one driving fator(round numbers are nice!)
1) The projected length (c) and side length (l) were used to find a suitable height for a coffee table (around 19" high)
2) Since the average coffee table is around 20" in height, choosing the correct lengths and angles were important in make an attractive table
3) A Law of Cosines and a Pythagorean theorem later, and I had a useful formula to implement in the CAD software.
Next up, CAD:
Step 2: CAD Modeling Steps
To make the CAD model, I used CATIA. The steps are as follows:
1) A starting point was created. The second point's sketch plane and the height were controlled through the formulas and created parameters (Also known as Knowledgeware in CATIA). Picture 2
2) A line connecting the points was then rotated around a central axis. This allowed for the central placement of each arm as well as giving a quick preview of the base design. Picture 3
3) After some adjusting, I settled on 15 arms for the table, they are aesthetically to me attractive as well as more natural-looking.
4) A rounded rectangle was padded to get the general arm shape.
5) For the arms to be more stable, a notch was created on each arm to lay normal (they lean on one another).
6) This was made via a pocket on a normal plane of the line previous to the pad. Picture 4, 5, 7
7) The tooling/base was created after projecting the arms onto a disk, and adding some tolerance around the part (so the arms can fit) and then pocketing the sketch.
8) The pocket was also patterned, and a hole removed the inner-part of the ring. Picture 6
8) The glass top was made just as as simple pad with two chamfers on it (AKA a Bevels).
9) The final step in creating the CAD model is the assembly, to make sure the to assemble the parts and check if any clashes (collisions of the parts) are present.
To make my assembly and each iteration of the base go together efficiently, global parameters were set-up at the assembly level that all of my parts used. It makes any change I make happen assembly-wide to make modifying the document MUCH easier.
The next step is the Drafting/ Tooling steps as well as working drawings. These make creating the physical part a breeze.
Step 3: Tooling and Working Views
One of the most vital things in this project is tooling. To make all of the parts, I am including drafted the plans for showing the accurate placement of the bottom tooling and notches. I also included the formats of: CatDrawing, PDF (for printing even if you don't have CAD software) and DXF of the base for laser cutting. All of the other tooling/drawings can be sized to fit when printing.
The files included are:
Technical Views- These are the dimensions for correctly positioning the notch on the arms,
Tooling- This drawing includes the necessary tooling to position the cutouts on the bottom bracer.
Tooling_Continued- Since Measuring an accurate 24 degrees (360/15 degrees) to space the holes on the bottom of the brace, I am including a template to make this easy.
Tooling_1- The include the notch templates on an 8.5X11 in sized paper for printing ease
All of the other tooling can be sized to fit when printing.
Now, it's just about to get real...
Step 4: Let's Get Physical
From start-to-finish, this project should take around 1.5 days or a weekend. It can be a one person project, but friends to help are always nice! Here is a list of Everything needed to make the table.
-Drill (with a bit large enough to fit the jig-saw blade through, your judgement, I used 3/16 in bit)
-Sandpaper- rough (75) to fine-(300) grits
- 36" x ~18" x 1" sheet of the wood of your choice (preferably hardwood) for the arms.
-18" x 18" x 1" sheet of wood the base
- 20" x 20" sheet of the material that will be the top surface
- 1 bottle of Wood Glue or equivalent adhesive
- Tape (scotch, electric)
- Scrap wood pieces
- 1 can of Spray Paint, Stain or Clear-coat
- Rubber mallet
- Willing friend to help
- Any Heavy weighted object (ie. bricks, textbooks, "willing" house-cat (not really))
- Glass would be the best material for the top of the table, but as a student, I'm on a limited budget so wood was my choice.
Before heading out to the workshop or garage, print off the Tooling and Tooling_Continued PDF documents from the previous step and take them with you to save trips.
Step 5: First Base
Time: 20-40 min
1) On the ~18" x 18" sheet, find and mark the center in both directions.
2) Cut out the radial lines of the Tooling_Continued.PDF.
a) Poke a small hole in the center of the radial lines.
b) Align the center of the tooling to the mark on the wood.
c) Tape down the cut-out.
3) (15x) Extend the radial lines out to the edges of the sheet using a straightedge or ruler. Picture 2
4) (15x) With the ruler, make a mark 7.5 in from the center of the radial spacing tooling.
5) Cut out the radial line tooling from the Tooling.PDF.
Cut close to the angled slotgraphicPicture 3
a) Extend the radial line on the cut-out to the end of the slot graphic. Picture 3
b) Poke a hole in the .25 in from the back of the tooling, along the radial line. Picture 3
c) (15x) Align the hole on the radial line tooling and trace the outline of the slot graphic. Picture 4
6) (15x) Drill holes at the marked locations with the bit (drill a pilot hole if necessary). Picture 5
Next comes all of the cutting/sawing in the project. Stopping at this point for now and cutting everything at once should minimize the amount of clean-up required.
Step 6: Do You Want to Play a Game?
Time: 45-60 min*
On the Table Saw:
1) (15x) With the 36" x 18" piece of wood, rip the pieces of the wood into 5/8 inch strips. Picture 2
2) (15x) Rip the strips a second time to get the square side pieces. Picture 3
*Using the Chisel/Dremel:
1) (15x) Position the Side tooling from the Tooling_1.PDF , by the dimensions on the Technical_Views.PDF .
2) (15x) Sketch the Top and Side profiles in the respective locations.
3) (15x) Take the carving tool of your choice and start.
I realize that carving the notch can be rather challenging. The flat surface will provide a solid surface for the glue to adhere to, provide an even sturdier table and a more professional result. The table is still strong enough if one chooses to skip this step. So I will be showing pictures of the table with the notch not included for those unable to complete this step.
With the **Jig Saw:
1) Cut out the sketched outlines on the 18" x 18" base
2) Take your time, fit the side pieces into the cut-out to see how they fit tight.
3) Enlarge with the jig saw or sandpaper the cut-out if the side pieces are too tight (no more than a mallet love-tap should ever be required)
4) If you are going to use the base tooling as part of the table, cut out the preferred radii, do not cut any closer than 1 in to the sketched outlines to insure the base holds during assembly.
Now we are ready for the gluing, and to see this pile of sticks come to life.
* The time was determined by skipping this step.
** Anyone who has a laser cutter can use the DXF file and make the base.
Step 7: Bonding Together
Time: Overnight, (8+ hours)
1) Slide the side-pieces into the slots, each piece is slid under the previous one placed.
*For those who made the notches, the correct orientation from Picture 1 is shown in Picture 2
2) Tap with the mallet (if needed), the pieces flush to the ground.
3) At this point the pieces should be free-standing in the tooling.
4) Carefully flip the stand over. Picture 4
5) Level, the base with the ground in all directions. (Since I was using pine as the base, some polite persuasion with a brick was needed to make my slightly warped boards level)
6) Space the arms of the base evenly with any spare wood Picture 4, 6
To make this assembly permanent, the wood-glue of your choice is needed.
1) Pour the glue into a cup
2) Apply to every side touching wood with a thin piece of wood (a cable tie worked good for me).
3) Clean up any drips that occur, this will make sanding easier.
4) Wrap the middle section with electrical tape. This is to make sure that each arm has even pressure bonding it together.
5) Wipe up any remaining drip 30 minutes after then wait for the glue to cure overnight.
So close, you're almost done!
Step 8: Finish Line
With the rough-grit sandpaper:
1) Round the edges off of the on the top and bottom of the base Picture 2, 3 This helps ensure that any high-point on the arms is now flush to the table.
2) Sand flushany glue that could have run down the legs and dried.
3) Also sand all of the exposed wood roughly.
With the fine-grit sandpaper
1) Mark every side lightly with a pencil. Picture 4
2) Sand the marks of the pencil away. This will help you to know all of the surface is has the proper amount of sanding done on each side.
Now that the base is smooth, vacuum or blow off the base to remove any wood dust.Apply any finishing touches to the base. In the pictures, I used satin-black paint for my base.
As the last step apply the top of your choice, if the top is glass or some other slick surface Bumpons from 3M or something similar, will hold the top in it's place.
That's it, your done, enjoy your unique spiral in your house. I used pine and no notches and the table was still strong enough. This way the design can be built successfully if you want to skip the carving and/or use lower quality wood. These decisions depend on how high-quality one wants to go in building the table
*If anyone want's a custom size of table, I would be happy to modify the working drawings and send them. Also, included are the CATIA model of the whole assembly as well as STL and STP files for importing in other 3d programs.