Fireplace Coffee Table

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Introduction: Fireplace Coffee Table

About: I'm an inventor / maker / designer based in the Bay Area. My background is in residential architecture, film set design, animatronics, media arts, exhibit design, and electronics. I use digital design and fa...

You can have an indoor fireplace safely in any home- no chimney necessary!

When you rent like me, you’re at the mercy of your landlord when it comes to home improvement. Nothing makes me feel cozy on a cold day like an open flame warming the living room, but there’s no way my landlord is going to spring for that.

Using an ethanol burner (carefully following the safety instructions), it’s perfectly safe to have an open flame without the need for a vent. With the right kind of fuel, there is no danger of harmful fumes tainting your indoor air quality.

The companies that make ethanol fireplace burners also make some very nice stand-alone fireplace fixtures, but for the limited space of my Bay Area apartment, I need my furniture to be multi-purpose. Hence, the Fireplace Coffee Table.

This is the first project I've made using my Wooden Nuts & Bolts process.

Step 1: Tools & Materials

TOOLS

Woodworking

Wood Tap & Die Kit

• Woodshop: Table saw or circular saw, bandsaw or jigsaw, drill press

• Random orbital sander

• Shop Clamps

Concrete

• Bucket & paint stirring stick

Acrylic

• Table saw or circular saw with plastic blade or scoring knife and straight-edge

MATERIALS

Wood

• Hardwood for the table slabs and wooden nuts. I used 2" thick Ash and planed it down to 1 1/4".

• Hardwood 1 1/2" Ø dowels. I used Red Oak Closet Dowels.

• Wood filler, wood glue, brad nails, liquid nails.

• Linseed Oil, polyurethane.

Concrete

Quickrete Crack-Resistant Cement

Cheng Concrete Pro Formula Mix additive

Cheng Concrete Countertop Polish

Ethanol Burner

Ignis EB1200 Ethanol Burner Insert

Bio Ethanol Fireplace Fuel

Step 2: Design

Fusion 360 is my go-to for furniture and product design these days. It's free for students and hobbyists, and there's a ton of educational support on it. If you want to learn to 3D model the kind of work I do, I think this is the best choice on the market. Click the links below to sign up:

Student/Educator

Hobbyist/Startup

This is the first furniture piece I’ve designed using my Wooden Nuts and Bolts idea, so I based the table on 4 threaded wood legs with nuts for rigidity. I designed it to be 2-tier, because my current coffee table with 2 tiers is really practical: you can move all the books, magazines, and empty coffee cups to the lower tier when you want to put a laptop on the top tier to watch a movie- or in this case, when you want to light a fire!

The manufacturer’s instructions call for specific clearances around the burner surface to combustibles. So to play it safe, I designed the table to have a 2 1/2” deep cast concrete surround for the burner insert. I wanted the top of the burner to be flush with the top of the table as well, so I designed the cast concrete part to have a 1/8” thick indentation. I left a 1/16” gap in the model for wiggle room between the burner and the concrete.

Step 3: Wooden Parts

The table measures 16"D X 33"W X 16"H when assembled. To make a 16" wide solid hardwood table, I planed down two 9" wide planks and edge-glue them into a single panel, and cut the parts out of that. If you're not used to cutting out complex shapes designed in the computer, check out my Digital Fabrication by Hand instructable.

Forstner bits will give you clean, consistent holes, and it's important to use a drill-press for this project. The holes must be flush and perpendicular to the surface of the table, otherwise you'll end up with crooked legs. When cutting out these parts, note that the top tier of the table (with the opening for the cast concrete) has threaded holes (meaning you start with a 1 1/4" Ø forstner bit), and the bottom tier without the cutouts has 1 1/2" Ø holes which allows it to slide freely up and down the legs.

For the legs, go to my Wooden Nuts & Bolts instructable. I cut the dowels to 16" segments and threaded the entire length of each leg. This allows the tiers to be adjustable, but I also really like the look of the "wooden bolt" holding everything together. There are 4 legs and 8 nuts- 4 nuts to hold up the loose lower tier, and 4 nuts to tighten against the threaded holes on the top tier.

Once the wood pieces were done, I took them to the table router to get a nice 1/4" filleted edge all around.

Step 4: Concrete: Test

In my first test with casting concrete, I added some expanded mesh because I thought it would mitigate cracking. I've designed rebar layouts many times for building projects, and wrongly assumed that the principals are scalable without limit.

I sifted out the aggregate from my concrete mix so that it would flow through the mesh easily. All the mesh did in the end was hold the concrete mix back and keep it from gaining purchase on the wood. The end result only had purchase in one corner- the rest of it was a crumbling mess filled with air bubbles.

The other problem with the casting test was that I didn't seal the wood in any way before pouring the concrete. As a result, the wood grain soaked up all the water from the concrete and made it swell considerably.

I talked to the nice folks at Cheng Concrete in Oakland, and they set me straight. They make amazing cast concrete countertops and furniture among other things and have a line of products available online that will allow you to cast concrete for just about any application in just about any color.

First, they confirmed that the mesh isn't doing anything to reinforce concrete at this scale. The other principal they pointed out is that the aggregate I sifted out is structural, and plays a role in keeping everything together, which is important even at such a small scale.

They recommended first sealing the wood to make it waterproof, then pouring the concrete. They also recommended their Pro Formula Concrete Mix- this helps mitigate cracking, increases curing time, and has the added bonus of coming in a bewildering array of colors. I went with Charcoal because I thought the contrast would be nice.

Step 5: Concrete: Mold

Having designed everything in Fusion 360, it was easy to make line work for all the parts of the mold. The mold is basically an 1/8" thick acrylic copy of the burner that is 1/16" thicker than the burner itself. This allows for an offset to give you some wiggle room to put the burner in.

ACRYLIC MOLD:

I used acrylic for the positive mold because it's rigid and makes for a very smooth cast concrete surface that doesn't require grinding or machining. With acrylic cut to size and welded with plastiweld, it's easy to get solid, air tight seals on all the parts.

Tap Plastics has a great tutorial on how to use acrylic cement to weld acrylic sheet together. For this mold, I cut the parts to size using the layout attached in this step, then built the box so that it was enclosed on all sides. Having no plans to re-use this mold, I decided to make it one monolithic piece, then break it apart with a rubber hammer and putty knife later.

CONCRETE CASTING:

I sealed the inside of the cutout on the table top with several coats of polyurethane to keep the water from wicking into the wood and making it swell.

Next, I aligned the cutout on the table top with the mold positive- this was easy to line up since I cut the bottom surface of the mold to the same size as the table top. I clamped the top down with more clamps than I thought I needed to get a tight seal.

Then, I mixed the Pro Formula into the concrete mix. I used 7LB of concrete mix, because I calculated that would fill the space about half way, which would be plenty. After stirring with a paint stirrer to get all the dry clumps out, I poured the mix into the cutout and let it cure over the weekend. 1 bag of Pro Formula mixes into 120 LB of concrete mix, so you have to do the math an measure the right amount for a smaller volume of mix. I have enough Pro Formula leftover for 20 more concrete cast projects after this.

Step 6: Concrete: Results & Reinforcing

The concrete came out beautifully for the most part. The top surface was very smooth without any break-outs or cracking.

Having sealed only the cutout though, there was a small amount of wicking in the top surface of the table from the edge of the concrete. Sealing the entire piece before casting would probably fix this. One of the shop guys also suggested just using vaseline around the edge of the cutout, which seems like it would work.

I added some joining dowels to the inside edge of the cutout before I poured the concrete so that the cured concrete slab wouldn't rely completely on the inside edges for structural support. Once the concrete was cured, I also added some extra wood structure to the underside with liquid nails- better safe than sorry!

I also used Concreteworks' concrete polish for the finished surface: wax-on / wax-off with a rag and this was done in 20 minutes. The result is a smooth, shiny concrete surface that would be perfect without the wicking at the edges.

Step 7: Assembly

  1. Thread one nut half way down the length of each leg. These positions should be consistent, since they will set the height of the lower tier.
  2. Insert the leg into an unthreaded hole on the lower tier.
  3. Thread another nut 1 1/2" down the top of the leg.
  4. Place the top tier and screw in the leg until its top is flush with the table top.
  5. Tighten the second nut against the bottom of the table top until it's rigid.

Repeat these steps for each of the other 3 legs. This is a good time to choose the pieces that came out the most perfect for the most visible placement.

The great thing about making this table with wooden nuts and bolts is that it's endlessly adjustable. Flip the table to its upright position and adjust the nuts until everything is flush and level.

This construction is ROCK SOLID. It's got serious lateral stability and can take a lot more dead load than it needs to. The wooden nuts & bolts scheme makes for a very robust finished product.

Step 8: Light It Up and Relax

This is a seriously versatile piece of furniture. The ethanol burner closes with a steel tool that's included, and after 15 minutes it's cool to the touch. You can use it as a fully functioning coffee table with a level surface 95% of the time, then clear off the top, pour in some fuel, and read a book by the fire on a cold night.

The burner is guaranteed by the company and comes with a complete set of safety literature. Follow the instructions and use common sense, and this is an awesome addition to the home you don't own.

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194 Comments

DEAR INSTRUCTABLES COMMUNITY,

Pier 9 is has the most stringent safety regulations of any facility I've ever been to. Shop privileges are revoked if you fail to wear safety glasses while machines are operating. Any product that is potentially flammable lives in a fireproof cabinet while not in use. We are not even allowed to have a wide variety of off-the-shelf adhesives here because of air quality concerns.

Before I even built this project, I vetted it with the company's OSHA certified Health and Safety Manager with all the documentation available on Ignis' website regarding the burner and the fuel, as well as my design and intended use. She had no concerns about harmful off-gassing, but since we're not allowed to have open flames of any kind at the Pier (that includes candles), she brought the project to the Fire Department to get a burn permit and a firefighter on standby with a fire extinguisher.

You know what the fire department said in so many words? "You don't need a burn permit for this project. This is fine for indoor use without ventilation."

3 replies

If you burn ethanol, doesn't it pollute/emit the environment only with water and CO2?

If i'm correct, there shouldn't be any danger, right? (not including having something catch on fire...)

Heck yes. Tell those haters like it is. :D

Good for you, well done

Jon, awesome table. Wish I had your skill lol

Beautiful idea, and very nice presentation. I may have missed a note about this in the Instructable, but how do you handle the fumes from ethanol combustion, if I remember my chemistry correctly, its C2H5OH + 3O2 --> 2CO2 + 3H2O .

The 2CO2 build up is very easly dismissed, but it's the majority of the reaction. And could build up if not taken care of.

,

4 replies

If the room is small enough, and sealed enough for Carbon Dioxide to begin to build up, Oxygen levels would be low enough to start creating Carbon Monoxide.

Said another way, you only need a standard carbon monoxide detector to run clean burning fuel safely inside. Build up of Carbon Dioxide will not be an issue.

The same issue would present itself whether you had this lit or not. Stick a human being in that same room and they will use up the oxygen faster than this burner!
But how many people do you know have access to air tight rooms??

We've got the formula now! Honestly, I just took the company's word for it regarding CO2 emissions. Apparently the amount of ethanol being burned isn't enough to be dangerous in a room that's bigger than a closet. The product and the fuel are both UL tested and have supporting literature, so I figured it was safe enough to be used once in a while. In any case, it's never triggered the smoke alarm in my house, but my cooking does often!

I may head out and see if I can find a bottle of this stuff and test
it. I have used organic ethnonol to study hypercapnia via respiratory
acidosis with the metabolic effects of hypoxia in club-horned
grasshopper (Aeropedellus clavatus).

Again nice build.

Very cool design even though the fireplace insert isn't quite up my alley. I really love the idea of the wooden threads, but I don't seem to be able to find much if anything at all on google where wooden screws or bolts are used .
I once took a very old desk apart that the top was fastened down with wooden threads. It really was a shame that it had been so abused because it was so well built that if I had to guess I would say it was over 150 years old, not an item you will ever find in the cheap furniture stores today.

3 replies

If you do not like the insert, you can use pretty much anything you like with Bio ethanol. I used it as a solution for my firepit table, and that was basically sand in a foil tray then soaked with bio ethanol and burn it. It works, plus you can either just have sand which you can draw designs into or cover it with stones or lava rock.
So you could basically throw in any insert you wanted to!

I think threaded posts were fairly common back then. I've seen a lot of furniture from the turn-of-the-century with threaded legs that screw into the underside of the table. I can see why they would do it that way- it's incredibly sturdy!

I think threaded posts were fairly common back then. I've seen a lot of furniture from the turn-of-the-century with threaded legs that screw into the underside of the table. I can see why they would do it that way- it's incredibly sturdy!

Можем поговорить подробней???

5 replies

Вы можете по электронной почте мне, если у вас есть какие-либо вопросы: jonathan.odom@gmail.com

Сколько себестоимость такого столика??? И можешь написать свою почту??

Горелка стоить около $ 50. Остальные материалов только дерево и бетон, таким образом, общая стоимость, чтобы весь кусок был около $ 120. Вы могли бы сделать это за меньше, если вы использовали более дешевые материалы, но я бы не рекомендовал использовать заменитель горелки. Важно, чтобы быть в безопасности. Моя электронная почта в моем комментарии выше.

google translate proving itself?