Wooden Fire Pit

Wooden Fire Pit by JON-A-TRON





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Manufactured fire pits all look the same. Make your own with hardwood, sheet metal, and off-the-shelf hardware store parts!

Step 1: Design




I loved the contradictory idea of making a wood burning fire pit out of wood, so I had to figure out a way to make that work safely. I played around with some cast concrete ideas at first, but I figured it would be much easier to just make a sheet metal bucket with a 1" air gap from all the wood.

That led me to the "clam shell" idea- a hatch with a screen that keeps sparks from flying. This in addition to the air gap seemed like the safest way to make a fire pit out of wood.

I went with Alder for the wood, 1 1/2" X 3" boards make up almost all of the wooden parts. Apparently Alder is the best wood to use when smoking salmon, so if the whole thing went up in flames I could break out the fish and the the project wouldn't be a total loss.

I used Fusion 360 for the design because it's a great solid modeling tool. It has mechanical assembly functions that let me test out the motion of the hatch, making the whole design process much faster.

Fusion 360 is FREE indefinitely with a "startup" license option after the 30 day free trial.

Step 2: Tools and Materials



TOOLS

Woodworking:
Saw for straight cuts: this could be a table saw, or circular saw.
Saw for curved cuts: this could be a band saw or jigsaw.
Japanese flush saw: this works great for joinery.
Drill: a drill press works best, but you can make do with a hand drill and a guide.
Bits: 1 1/2" forstner bit, 1 1/4" forstner bit, countersink bit
Doweling Jig
Chisels: for the bridle joints.
Mallet (for fitting and chiseling)
Clamps

Sheet Metal:
Jigsaw with metal cutting blade (fine teeth).
Hand drill with 1/4" metal drill bit.

MATERIALS
2X10 hardwood boards (about 13 linear feet). I used Alder, but most hard wood will last outside if finished properly.
1 1/2" dowel (about 12" total), 1 1/4" dowel (about 4' total), 1/4" joining dowels
11 GA. stainless steel sheet (34"X32" total material). You can use mild steel for this, it's a lot cheaper and you can get it off the shelf at Home Depot, but it will rust out in a few years to be sure.
Fireplace curtain screens. These make the protective screen that encloses the metal enclosure.
1"X1/2" corner b, 1/4" Ø machine screws 1/4" long, and nuts.

Step 3: Cutting Pieces Using Templates




For details on how to use templates to cut out complex geometry, go to my Digital Fabrication by Hand instructable. These templates are at 1:1 scale, and if you print them at 100% size at a print shop (Kinko's has large format printers), you'll have everything you need to do the cutting.

The Digital Fabrication by Hand example uses plywood, but the same technique works with metal and hardwood.
CUT TEMPLATES INDIVIDUAL.pdf160 KB

Step 4: Laminate the Pieces



The sides of the fire pit are laminated to make a single panel. The two longer ends with the rounded tops make the legs, and the board in the center protrudes to attach to one of three shelves that hold up the bucket.

I didn't bother with biscuits or dowels since the boards are 1 1/2" thick.

Step 5: Joining the Arm Parts



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To join the arms into an L shape, I used joining dowels and a dowling jig. The dowling jig lets you perfectly align holes between parts quickly and ensures that your holes are perpendicular to the surface of the wood.

The reason you need either dowels or biscuits (or and other fancy joinery cutting) is that end grain doesn't glue. I didn't want exposed fasteners on the wood, so I went with dowels for this part.
Clamp the two parts together so that they are aligned edge-to edge. They should be "mirrored".
Mark the centerlines of your holes with a square across both pieces.
Align the jig hole with the centerlines, and drill the holes. The depth is important because you want to get the most purchase out of the dowels. Make sure each hole is just over half the depth of the dowel that you'll hammer in.
Squirt in some glue and hammer in the dowels, then hammer the pieces together.
Clamp the pieces the eliminate a gap between the faces of the wood being joined.

Step 6: Joining the Shelves [FAIL]





Since I was already using them, I went with joining dowels to attach the shelf elements to the panels of wood. This should work in theory, but the problem is that each board needs 2 dowels on each end. That means there are 12 separate holes to align between 3 separate boards. I found this to be pretty much impossible, so I ended up cutting off a dowel from each board so there were only 3 holes I needed to align at once.

So when the glue dried, one of the panels was held on by a single dowel on each board. Now I understand why people use biscuits- there are no holes to align.

Step 7: Screwing the Shelves Together [WIN]







Since I didn't want exposed fasteners on the wood, I decided to countersink the screws and hide them with dowels. This part is pretty straightforward- the countersink bit drills a pilot hole for the screw plus a shallow wide hole for the screw head.

Once you've got the screws in (screwing them into clamped, glued pieces), add a drop of glue and hammer in the joining dowels.

A japanese flush saw to trim off the end of the dowel works really well- it keeps you from scratching the surface of the wood when you're sawing.

Step 8: Attach the Legs








The legs are joined with a bridle joint. The geometry is laid out in the the templates with measurements. I used a japanese flush saw to cut the sides, then chiseled out the back end of the female part of the joint.

When chiseling, it's important to clamp a guide board aligned with the edge you want to chisel out- this keeps the chisel flush. I used a file to clean up the edges.

The bottom treads of the legs have the male ends. After cutting one on the band saw, I used it as a template for the other leg.

Then I glued and clamped everything together, and added a countersunk screw and dowel for extra stability.

Step 9: Assemble the Clam Shell









The hinge action comes from a dowel glued into the larger hole on the top of the clam shell arm, and fitting snugly into the hole on the side of the wood enclosure. The dowels we had in the shop were actually 1 5/8" Ø and 1 3/8", so I had to sand them down to fit the holes. It would have been prudent to measure the dowels before designing the piece and drilling the holes.

The dowels at the back act as a hinge, and the dowels are pins that hold the clam shell in a closed position. All four dowels are 3" long.

Step 10: Sanding and Finishing





Once the wood glue is cured, it’s times to sand and finish everything. I used an orbital sander to do most of the work and stopped at 100 grit. You could go finer and the piece might last longer- fewer nooks and crannies for water to creep into.

After sanding I used an off-the-shelf deck finish on all the wood, applied twice with 1/2 hour penetration each time.

Step 11: Assemble the Fire Bucket




After filing down the edges of the metal pieces, I started bolting the parts together. The fire bucket templates are set up for 1"X1"corner braces, so with the screws I mentioned in the Tools and Materials step, the whole thing fits together really quickly. The bucket is open in the front and has extra holes for attaching it to the wood via standoffs.

Step 12: Attach the Bucket





If you cut all the pieces to size, you end up with a consistent 1" gap between the wood and the bucket on all sides. Using some 1" MDF scraps, I clamped the bucket to the wood enclosure and aligned it so that it was centered on all sides.

Using standoffs I made by cutting a 1/2" steel tube, I aligned them with the holes in the steel using a pair of pliers and screwed the wood and steel together with stainless steel screws. I fastened it in 4 places at the top of the sides, and in 4 places on the bottom. The bucket is very snug with 8 screws attaching it to the wood.

Step 13: Attach the Clam Shell





Having made sure everything fit together properly, I then moved on to attaching the clam shell.

The dowels that make the handles are 1 3/8" Ø, so I had to sand down the ends to make them fit into my 1 1/4" holes. Don't do it like me kids, MEASURE TWICE, CUT ONCE.

Laying one arm with the handles attached on its side, I glued the holes, fitted in the fireplace, and hammered everything together with a rubber mallet. I let it sit overnight with clamps on the handles for go

Step 14: Assemble the Screen










The screen is very important. Without it, you might ignite the wooden part of the fire pit with a flying spark.

The screen I found is a curtain for a brick fireplace- it comes in two sections that are 18” X 24”. I designed the pit so that the screen would cover the open side of the bucket, wrap over the top, and cover the back of the bucket as well. This way, you get complete protection over the open part plus an extra barrier at the back of the box, which will undoubtedly get super hot.

To connect the two curtains, I just threaded some wire through the open end of each side. I started with bailing wire, but I ended up using welding rods- they are stiff enough to keep the screen from slumping in the middle.

With the two screens connected, I added a rod at the front end. To keep it in place, I looped it back to make a hook. Once the first rod was in, I screwed it into the bottom of the wooden flanges on the clam shell using washers and wood screws.

I then wrapped the screen over the top of the pit. At this point I realized that I could just use the existing bolts on the fire bucket to attach the screen on at the back, so I broke out some 1/2” long bolts and added a washer. It’s important to use two nuts for this- the first nut keeps the box securely fastened, the second nut with the washer just holds the screen on. You’ve got to make sure the bucket is secure, because the heat will undoubtedly warp it.

With both ends fastened, I then added more rods along the top of the screen to keep it from slumping. The placement of the lower rod on the front makes the screen fold under the front of the bucket, this keeps anything from spilling out.

Step 15: Start the Fire








Starting a fire seems to work best by doing the tipi method leaning against one of the corners. Paper in the center, kindling over that, logs over the kindling.

Once it’s going, kick back and enjoy it! Don’t worry about the wooden handle across the top that’s precariously close to the blaze, I’m sure it will be fine.

Step 16: Rethinking the Design






After about 10 minutes of watching the fire and touching the wood to see how hot it was getting, my wife (the ever present voice of caution) convinced me that this is a stupid feature that’s useless after you’re done carrying the thing, so I cut it off. More fuel for the fire!
Step 17: Done!





We watched it carefully all night, testing to see if the standoffs were conducting enough heat to cause a problem, making sure the screen was staying in place, making sure no errant sparks were getting out, all the while having a fire extinguisher at the ready. It works great, and it looks awesome!

We’ve just has the worst storm in 10 years and the pit’s been sitting out in the rain. The deck finish is doing its job- water just beads and runs off. I know I’ll have to refinish it in a year, but it’s worth it.