[Ecocandle]

Mahogany Kitchen Stool Project

Well, here we go. I have been working on the design and preparation of this project for 3 years. The final prototype was just completed.



This is my second prototype. The first one was a quick (that is a relative term) mock up to see if I had the size correct. I built this out of scrap 2×4s and screws. Pieces were only roughly shaped. After building this, we determined that it was about a half inch too tall.



The second prototype was built as a prelude to actual construction. Each stool has 42 mortise and tenon joints. Several of them are angled and others are on curved parts. By making a full prototype, I have a scale pattern to verify the layout of each piece before I cut into my lumber.



Also, I get a chance to make mistakes and learn. I ended up missing on three or four dimensions and had to patch parts up. I have chosen to form the curved parts by laminating thin strips. The two curved boards on the back formed very well, but the 5 slats did have some spring back. I'll need to adjust the form or move to thinner strips. Stay tuned on that one.

Finally, I get one last chance to check my design choices. In this case, my wife and I felt that the slats on the back were spaced a little too far apart. It ended up crowding the gap to the legs. I changed the design and moved the slats a little closer together.

I'll outline how I intend to proceed with this blog. I'll post updates on the construction as I go. Woodworking is a spare time activity for me. Weeks may go by with only a little activity. I'll post a few "flashback" entries where I will cover my design process.

I'll also keep a log of construction hours. This will not include design or prototyping time.

Cutting rough stock : 2 hrs
Cutting legs to width and thickness: 4 hrs 20 min
Cutting thin stock for seat back laminations: 3 hrs

Total so far: 9 hrs 20 min

I really like the design, I also like hearing the process you went through.

 

[Ecocandle]

Preparing Lamination Strips

There are three curved parts in each stool. These are formed by gluing up thin strips to create a thicker laminated part. The three parts are:

1. Seat Back - 7/8" thick (formed with 5 or 6 strips)
2. Back Rest - 7/8" thick (formed with 5 or 6 strips)
3. Slats - 3/8" thick (formed with 3 or 4 strips) (5 per stool)

As I plan the construction, I start to realize that I have 6 stools with 7 curved parts each. That works out to 42 glue ups. Each one requires a full day for the glue to cure. I do have three different forms, but this is still a lot of time - 30 glue ups are for the back slats. I need to get the glue up process started first. I can work on shaping the other pieces while the glue dries on the laminated parts.

The 7/8" thick parts were prototyped with 6 layers. They formed fine with no spring back. I prefer to use fewer, thicker strips and end up with one less glue joint. I'll be testing out the first glue up with 5 strips and see how it goes.

The 3/8" slats were prototyped with 3 layers. There was some spring back that made it difficult to align parts for assembly. I need to reduce the spring back. My plan is to try to modify the form and test it with another prototype glue up.

The wood for the laminations was resawn off the Back Leg stock. I ended up with pieces about 1/2" thick and 3 5/8" wide. They were long enough to provide two pieces for the glue up. I then resawed these to give me 2 long strips. Now I am up to 4 pieces for the glue up.



I figured I would share some of the things I do when resawing. First I use a 7 1/4 inch thin kerf blade. The kerf is only 1/16". This helps me get the most out of each piece. If the board is too wide, I need to stay with one of my larger blades. I do not have a zero clearance insert (yet), so I use a long scrap of thin plywood and clamp it to my saw table. I raise the blade through the plywood and I end up with a temporary zero clearance solution. Finally, I use a marking technique to keep track of which board each pair of strips came from.

I use my hand saw and make a set of marks across the end of the board.



In this case I have marked this piece as belonging to stool number 4. By angling the marks, I can return the two pieces to the same orientation as before the resaw cut. Each stool has 2 boards (one for the Seat Back and one for the Back Rest). I mark the second board for stool number 4 with 4 cuts, but I place them in a different spacing.

I now have strips of wood that can provide 4 pieces for my glue up, but I need 5 or 6. Fortunately, my strips are wider than I need. When I rip them to the desired width, I have two narrow pieces left over. In the case of the Seat Back, these two narrow strips can be glued together. This way all the wood comes from the same board and I should be able to keep the colors matched.



Once I let the glue dry and clean up the piece, I have 3 strips of wood. Each is long enough to give me two pieces for a total of 6 parts for the lamination.



The strip on the right is the glued up one. The Back Rest is wider. As a result, my left over pieces are not wide enough to make the third strip.



In this case, I have added a third piece of left over stock to make the strip wide enough.



This entry is long enough. I'll cover more later.

Current time log:
Cutting rough stock: 2 hrs
Cutting legs to width and thickness: 4 hrs 20 min
Cutting thin stock for seat back laminations: 3 hrs 35 min
Prepping laminations: 2 hrs 20 min
Glue up Laminations: 35 min

Total so far: 12 hrs 40 min

This is really cool. I love the write up, I can't wait for the next installment. It is fun to read about grown up woodworking.

 

[Ecocandle]

Setting laminations to final thickness

Once I have the 3 lamination blanks cut to width I thickness sand the strips to reach the final dimension. I have tried using my planer, but when the strips get this thin it is easy to end up with damage. I set my ShopSmith up as a disc sander and use a thicknessing jig. I first showed the use of this in a previous blog. There was some interest in a more detailed description so here it is.

Here is the setup.



Basically it is a 3 1/2 inch tall bullnosed block clamped to the fence. The block is set up closer to the edge of the table than the desired final thickness of the strip. In this case I want strips 0.175" thick so the block is set about 1/8" from the edge of the table. The disc is initially positioned from the block at the current strip thickness (just over 0.2 inches in this case). I take advantage of the quill advance capability of the ShopSmith and move the disc closer to the block after each pass.



The construction of the block is pretty staright forward. I cut a bevel on each end of a 2×4 leaving about 1/4" flat on the end. I then cut the beveled end off making sure I had enough length to accomodate the clamp I will be using. Make sure the cut is square. Then mount the beveled piece to a cross piece. The final step is to true up the edge. I clamped the block to the fence and set it up hanging over the table. I then advanced the disc against the block. This way I have the functional edge of the block exactly parallel to the disc.



Once this was done I marked the top side (see top two photos). If I were to flip this over, I might get tapered width strips (that would be bad).

A final set up element is to mount a dust collection hose underneath the table next to the disc. I don't always do this, but this project has a lot of strips to sand. In no time, I had my shop coated with fine mahogany powder. The hose does a good job of collecting most of the dust. I took this shot while sanding a strip. You can see some of the dust in the picture.



Finally, here are a few operating tips.

1. Do not let your fingers touch the disc! Use long strips - they should extend 3 or 4 inches past each side of the disc to give you good finger access.
2. Set the block up to contact the disc on its downward motion. Setting block close to center can result in the strip being pushed back at you.
3. Feed the strip in until there is only 3 or 4 inches of strip left, then pull the strip out on the exit side.
4. Allow about 3 inches on each end as waste. The strips can taper a bit as you start the strip or pull it out.
5. Keep the strip feeding in as straight as possible. Letting it bump against the disc any where but at the block can result in gouges.
6. The exception to #5 is if you are sanding very thin strips. Then the strip can fall between the table and the disc - in fact there may be no table exposed past the block. In this case rest the strip on the table, bend it into the gap and bend it back onto the table once you can reach it safely. I have managed to sand strips as thin as 0.02"
7. Use light passes. I take off about 0.005 each time. You can force a bigger cut, but I worry about deflections and not getting a consistent strip.
8. One time past the disc will not remove all the material. I have made as many as 5 passes without changing the spacing.
9. You can control how much is removed in a pass by how quickly you feed the strip. This gets easier on the 2nd or 3rd pass at the same gap between the fence and disc.

I have been using this method for several years. I am able to set my strip thickness to within 0.004" (+/- 0.002").

If you have a conventional disc sander, you could shim the block closer after each pass - or get fancy and build an adjustable version.

The next entry will cover glueing up some curved parts. As always, comments are welcome.

Current time log:
Cutting rough stock: 2 hrs
Cutting legs to width and thickness: 4 hrs 20 min
Cutting thin stock for seat back laminations: 3 hrs 35 min
Prepping laminations: 3 hrs 20 min
Glue up Laminations: 1 hr 35 min
Trim Laminated Parts: 15 min

Total so far: 15 hrs 5 min

I really like it that you include the time data at the end. Very cool indeed.

 

[Ecocandle]

Finding shop time in a busy schedule -or- Making slats & cutting pieces

The next step in this project is making the curved slats for the back of the stool. The process is the same as for the curved parts with a couple exceptions. First the pieces for each set of slats are cut from two blocks. These blocks were next to each other when cut from the large stock. Instead of marking with a saw cut as I did last time, I used a permanent marker.



By angling one stripe across both blocks, I am able to keep the strips in order. The total number of stripes tells me which stool this set of strips belong to.

The other difference is the clamping jig.



This jig has two curves and required careful adjustment to create a tight fitting result.

But, this is not what I want to write about for this post. I think it would be nice to share how I find shop time. We all have busy schedules and, at least for me, the woodshop takes a lower priority. I find that I can fit in shop time a little bit at a time.

I start out with a stack of strips to be glued up. This makes a good example of how to find shop time.



My shop is located off the back of my garage. Gluing up a set of 4 strips takes 10 to 15 minutes. If I can find that much time before I leave for work, I have enough time to glue one more set.



As the days go by, I find that the pile slowly shifts from only one done to only a few left to do.



And then the day comes when I have glued the last one up!



Then there are days when I have more time. That is when I can take the rest of the wood and start to cut it into final pieces.



In this case, there is a bit of prep work to make sure that the grain runs from one part to the next wherever possible. There were several 15 to 30 minute sessions where I just focused on marking the pieces.



Once again, cutting the pieces is done a little bit at a time. The longest session was less than 2 hours. Over time, the pile of big parts turns into a pile of smaller parts.



And once again, the day came when the last pieces were cut.



There is likely some extra time in this project that results from working in small sessions. For me the tradeoff is that I get to make progress and spend time in the shop more often.

The project is now to the point where all the pieces have been cut to thickness and width (well almost all … ). Next is cutting to length and then cutting mortises.



Current time log:

Cutting rough stock: 2 hrs
Cutting legs to width and thickness: 4 hrs 20 min

Seat Back and Back Rest
> Cutting thin stock for laminations: 3 hrs 35 min
> Prepping laminations: 8 hrs 40 min
> Glue up Laminations: 3 hr 50 min
> Trim Laminated Parts: 2 hr 25 min

Back Slats
> Cutting thin stock for laminations: 1 hr 55 min
> Prepping laminations: 3 hrs
> Glue up Laminations: 6 hrs 5 min
> Trim Laminated Parts: 10 min

Lower rail parts
>Cut to width and thickness: 10 hrs

Total so far: 44 hrs (7+ hrs per stool)

That was a great blog post. I love the approach you take to the project. I can't wait to see the next steps and the finished project.