Filing Cabinet Smoker - Prajwal Tumkur Mahesh

The bureaucrat’s barbecue pit

I am an enjoyer of barbecued meats but this dependence is not so good for me financially. My humble graduate student income can’t buy me these tasty hunks of cholesterol and protien but, as an addict, I wasn’t going to let a simple lack of funds stop me from living out my dietary aspirations.

When I refer to barbecue, I’m talking about cooking (primarily, but not restricted to) meats slowly over an indirect heat, using wood smoke and other seasonings as the main flavorings. Flavors of barbecue vary regionally and from state to state, influenced not only by local traditions but by ingredients available in the area. Over many hours, this smoke deposits and the low heat breaks down the connective tissues in the meat, allowing even tough cuts to become tender and delicious. A smoker, or a barbecue pit, is typically the tool used for this job.

The high prices of commercial barbecue are of consequently not entirely the fault of the restaurateurs—this is a process that demands time and resources. However, if I wanted it cheaply, I was going to have to learn to do it myself.

Smokers can be (and are) made out of anything, from a hole in the ground, intricate piles of cinderblocks, all the way to polished stainless steel enclosures. Each geometry and material choice bring its own advantages and disadvantages but essentially, a smoker only needs two things.

A chamber for the meat to sit
A source of heat and smoke

Typically, this is set up in such a way that the meat is never directly exposed to the heat source. Rather, an indirect but controlled amount of heat and smoke are allowed to enter the meat section. The low heat cooks the food while the smoke collects on the meat to provide flavor. An automatic pellet smoker for example would use a regulated electric heating element to warm the meat chamber and produce smoke from compressed wood pellets.

I decided to use charcoal for my heat source because I wanted the experience to be as manual as possible. For me, half the fun would come from the hands-on process of monitoring the fuel and adjusting the air vents to maintain cooking temperatures inside the meat chamber. These coals would periodically get chunks of wood thrown on top to smolder and release smoke.

As described, these coals would need to be separated from the meat by some kind of barrier so that direct high heat would not prematurely overcook the meat. While thinking about all of this, I found this perfectly sized two-drawer filing cabinet in the recycling.

Things on This Page

Build

There are many examples of filing cabinet smokers around on the internet. The separate drawers give adequate separation between the fuel and the food and the enclosed volume is great for enveloping the meat in heat and smoke while it cooks.

It was gonna take a little bit of work though to get this box ready for cooking in.

Prep and Paint

First up was taking the cabinet apart and removing anything that could produce toxic byproducts when heated. This included any plastic or galvanized parts along with and unnecessary painted components.

I removed all the file hanging hardware form the drawers, but left the aesthetic components on the drawer faces intact. I wanted the end product to still maintain some of the visual elements of the original filing cabinet, so the handle and label holders were left on.

Next up was stripping the existing paint from the cabinet. I didn’t know what this was made of, and I didn’t want it decomposing under the heat and releasing anything harmful onto the food. I grabbed myself a bottle of this citristrip, coated the cabinet, and wrapped the whole thing in plastic wrap to slow down evaporation of the stripping solvents.

I let this stuff sit and soak for several days but this paint would not budge. I even tried multiple coats of the Citristrip, as well as more aggressive solvents like acetone or toluene with absolutely no luck. I never figured out what type of coating was on this guy but no solvent I had access to would even touch it.

Even using a propane torch to try directly burn off the paint didn’t do much other than discoloring it slightly. The silver lining with this experiment though was that it told me the paint would not peel or blister at high heat. If it could survive the blowtorch without even smoking, it would survive the mild 300F (max) heat of cooking. I was going to put a coat of high temperature paint over everything and knowing that the existing paint was stable, I could paint right over it without worrying about it flaking off.

I managed to mechanically remove this much using a razor blade scraper and a wire brush, but gave up after a couple days of this. I used some sandpaper to lightly scuff up and finally wiped everything down with rubbing alcohol to prep for painting.

The outside of the cabinet recieved a full can of this Rustoleum High Heat Ultra paint to protect it from rust. The inside of the cabinet was left unpainted and bare, since I wanted to minimize the amount of paint close to the food.

I masked off the drawer hardware and sprayed the remaining outside-facing surfaces down with the black high-heat paint.

On top of the cabinet, I drilled a 1″ hole and installed this dial thermometer to measure air temperature inside the cooking chamber.

This is mostly cosmetic since I was going to be using a set of probe thermometers close to the food to monitor the air temperature more accurately.

Once the paint had been allowed enough time to cure, I removed the masking and threw a bunch of coals into both cabinet drawers. I ran in the box at 400F-450F for a couple hours to stabilize everything and drive off any potential VOCs that might otherwise settle on the food.

Laser Marking Stainless Steel Labels

Just to be a little extra, I decided to make some heat-proof labels to stick into the front-facing label holders on the cabinet drawers

I cut a couple of blanks out of a stainless steel sheet and applied a coat of CerMark compound on both.

Stainless and most other metals can’t be engraved directly using a CO2 laser cutter because too much of the light just reflects off. The CerMark, on the other hand, absorbs the laser’s IR wavelengths strongly. It heats up and bonds to the underlying metal anywhere it is hit with the laser. The un-lasered compound is washed off with water, leaving the metal and a permanent dark marking behind.

I made sure to also engrave the border of the labels onto the metal blanks. I could then use a shear and a disk sander to trim the labels down to that outline.

All done. These will be able to resist cooking temperatures and survive outside without rusting.

Machining Handles

For an additional little bit of flair, I wanted to add some handles across the top of the cabinet. I could also put a board across the top of these handles and create a surface for food prep.

The handles themselves would be made out of 1.25″ wooden dowels but I needed to make some clamps to attach them to the top surface of the smoker. I started with this pile of scrap 1/2″ aluminum plates and cut out some chunks that would be big enough to fit the part.

In the mill, two holes were drilled, expanded, and tapped for 1/4-20 screws to clamp these appropriately sized chunks to a sacrificial fixture plate. I needed this because there wasn’t really another good way to clamp the pieces in the vice directly and machine the full profile.

I laid out a basic 2D profile toolpath in Fusion 360 to cut out the main shape of the clamps. I designed the clamps to be machined using a 1/4″ endmill, so I had to be a little conservative with the size of stepdown. The diameter of this cutter is limited by the gap it has to fit through in the mouth of the clamp.

The freshly machined clamp body is drilled and tapped to accept a 1/4-20 screw. This is what allows the clamp to tighten and grip the dowel rod. They also receive clearance holes on their base through which they will be secured to the top of the cabinet.

I repeated this process three more times to make a total of four clamps.

The dowels themselves didn’t need too much work except for a light sanding and a couple coats of butcherblock conditioner to protect them from water damage outside. I didn’t know too much about wood finishes at the time, so you won’t be surprised to hear this washed off pretty much the first time it rained. I ended up putting on a couple coats of a more durable polyurethane.

The locations for the clamps and rods are marked on top of the cabinet before drilling clearance holes for more 1/4-20 screws. I machined nutplates (sadly not shown here) with matching threaded holes that went inside of the cabinet to secure the clamps in place.

Lastly, I cut the excess length off of the dowels. The ends were sanded and finished with several helpings of the butcher block conditioner.

Installing Air Control Vents

To allow air into the coals chamber and smoke out of the meat chamber, I needed to addd some adjustable venting. The primary way to control the temperature inside the smoker is to adjust the amount of airflow to the fuel source, so it was important that I had good control over this. To save some time, I purchased these radially adjustable vents from amazon.

I didn’t have a way to cut a hole the full size of the vents, so I marked their location and drilled a collection of smaller holes within the footprint.

I covered the bare metal edges of these holes with a little bit of the high heat paint to avoid rusting.

With these vents in place, the main body of the smoker is complete.

Welding Stainless Cooking Grate

I needed a grate of some kind of surface to hold the meat inside the top drawer. It would be kinda goofy to put the meat directly on the bottom of the cabinet, especially since that would be directly heated by the coals underneath. Moreover, it would be nice to have space for a drip catch or water tray under the meat.

I picked up these stainless steel grill meshes at a nearby supermarket for a couple of dollars. These are too big and too flimsy for what I need, so some modifications were in order.

I started by cutting off one of the framing rods along the log edge and clamping it at the width I needed, around 32cm.

This is TIG welded in place.

To attach the mesh back to the frame rod at the new location, I tried at first to use the TIG torch. Even at minimum amperage, it was too hot and kept melting the frame wires.

I gave the spot welder a try instead and this actually ended up working really well.

The remaining excess mesh was trimmed off using a cutoff wheel in an angle grinder

I cut two more frame rods from another grate and welded them in to support the frame in the middle. These just brace the mesh and prevent any bowing once loaded up with 10-20lbs of pounds of meat.

Quick Charcoal Chimney Build

One of the chemicals I use for my research shipped to me in this stainless steel tin. I had couple hours free after work and as a little side project, I figured it would handy to turn this into a charcoal starter chimney.

Handle

The handle for the chimney was made of the same 1.25″ dowel I used for the smoker handles.

To attach this to the frame, I bent a pair of 1″ wide steel flat bar sections into right angles

I drilled some holes to attach the dowels with screws. The other end of the bars received holes for rivets.

Three rivets on the top and bottom fixed the handle securely to the can

Chamber

I cut the base out of the steel can using a plasma cutter.

With a thicker sheet of stainless steel, I plasma cut another circle using this laser cut template. This platform would support all the hot coals, so I wanted it to be a little more substantial than the circle I cut out in the last step.

I am clearly no artist with this tool, but this will do just fine.

Used a step drill bit to punch some holes into this plate. This will be more than enough for adequate airflow.

I cut a few right angle tabs and spot welded them to the outside of the circle.

These were then spot welded to the inside of the canister to mount the plate a few inches up from the bottom. This lower chamber would be filled with paper or some other material which when lit, would in turn heat and light the coals above the platform.

I drilled some holes around the base for airflow as well as a few more supplementary holes higher on the canister. Rising hot air inside the chamber will pull fresh air through these holes and add oxygen to the coals as they smolder. This thing actually works almost too well—if I leave it unattended for more than 5 minutes, it reduces a full load of coals into ashes.

Here it is in action.

Barbecue

Finally it is time for food. Since I still had to learn how to use the smoker, I wanted to start small. The first attempt was done with cheap potatoes and sausages, since it wouldn’t be a big deal to ruin these.

That worked extremely well and I graduated to pork butt. This was smoked over a combination of cherry and hickory with a few onions thrown in once in a while for flavor.

These pork spare ribs also turned out great. These were also smoked over cherry, braised with apple cider and butter, and then glazed with a texas style barbecue sauce.

The barbecue sauce was given a little longer in the smoker to set up and get sticky.

These were brisket burnt ends. I seasoned these just with salt, pepper, and garlic before smoking with mesquite. Similar to the ribs, these were braised in beef broth and butter before being coated with a Kansas city barbecue sauce and allowed to caramelize.