A DIY Oven Made from a Filing Cabinet (For Under $50!)
We recently made a fully functional DIY oven for the home workshop using little more than an old filing cabinet and ceramic heating elements from old room heaters!
The split, two door-ed oven is capable of operating at sustained high temperatures of at least 500°F (~260°C) with ease. It is surprisingly thermally efficient and temperatures remain relatively cool on the outer skin of the oven at all times.
The DIY oven is not fine art from any engineering or appearance perspective, but it is a masterpiece when considering how how well it performs and how useful it is in the workshop. Doubly so, considering we spent less than $50 and a only a couple of fun days in the workshop building it.
Both hobby and industrial grade ovens of similar size and heating capacity would run into the many thousands of dollars to purchase new.
Our DIY filing cabinet oven has surpassed our wildest expectations as a reliable, viable and highly adaptable piece of workshop heating equipment.
Design and Purpose of DIY Oven
The DIY oven was built from a filing cabinet and spare junk parts, mainly because we needed the cheapest possible DIY heating solution for curing electrostatic powder coating. Our CNC machined aluminium parts and steel design projects do not typically justify large financial outlays for large extraneous equipment like professional curing ovens.
The DIY oven was built without any planned initial design in mind. We came up with the design and ideas for the build as we went along.
Once we started cutting the filing cabinet apart, we were more hopeful rather than confident that the the following goals might be achieved.
- To build a DIY oven capable of reaching and sustaining a working temperature of at least 400°F (~200°C) for cycle times of approximately 20-30 minutes. (Preferably without starting fires in the workshop or electrocuting anyone!)
- To make a DIY oven with large openings and easy access doors which swung horizontally.
- To achieve relatively even distribution of heated air inside our oven without strong air currents that might disturb uncured powder paint surfaces.
- To build a DIY oven which vented little or no air during operation, due to the carcinogenic nature of the gases released by curing powder coat paints.
In the end, the results spoke for themselves. We achieved all goals with absolute success and are amazed at how well the DIY oven works.
We initially needed the oven for finishing CNC milling projects and curing larger powder coated metal parts and designs. But we now also use the oven for a variety of other DIY applications. This includes: heating acrylic sheets before bending (ie: bent using our DIY Acrylic and Metal Sheet Bender); softening plastics before vacuum forming; scorching pine wood (for a ‘traditional Japanese styled’ look in our projects), and heating bamboo to dry and seal the wood surfaces naturally before use.
There is no doubt, the oven is proving to be an extremely handy tool to have around.
Overview – From Filing Cabinet to DIY Oven
Our DIY oven was made using a standard four drawer office filing cabinet as the base enclosure. The oven cabinet stands approximately 120 inches (120 cm) high, 25 inches (65cm) wide and 27 inches (70cm) deep.
The structure was stripped of all combustible components, locking mechanisms, drawers and drawer railings. This involved a reasonable amount of angle grinding work.
Two hinged doors were made by pairing the front metal panels of the four original cabinet drawers. Simple swivelling door lock mechanisms were made out of strips of metal from the original file drawer support rods.
Heating elements, still with their heat reflective enclosures, electrics and dial switches intact, were removed from the outer housings of two disused room bar heaters. It should be noted that these were the older style heaters with ceramic element heating bars as opposed to the newer infra-red bar heaters. (True heater bars use hot tungsten wires that transfer their heat to a ceramic core. This in turn heats the oven air. Infra red heaters however, do not heat air directly. They only heat objects and surfaces which are subject to the infra red radiation. Infra red elements do not directly heat air themselves.)
Rectangular holes the same size as the element enclosures were cut into the side of the oven and the heating elements were attached securely.
An insulated false floor was made in the base of the filing cabinet in an effort to stop heat loss into the cold workshop floor during operation (and to prevent the risk of fire if the floor got too hot).
Sheet metal from the base of the original drawers was cut, bent and shaped to form outer protective enclosures for the heating elements. The same was done to protect and securely hold the electrics of the on/off dial switches. All of the fabricated enclosures were riveted to the outside of the newly transformed DIY oven.
All significant holes which could allow air to escape the oven were sealed with strips of heat safe 100% aluminium tape.
All doors and walls of the cabinet were then lined with a continuous initial layer of standard aluminium kitchen foil (shiny side facing in), using heat safe aluminium tape again to stick the sheets in place.
Matted fibreglass sheet was cut to approximate size and was snugly fitted to all internal surfaces and walls of the filing cabinet. We ensured the fibreglass matting was well overlapped in all corners.
Drill holes were made in the metal walls of the oven and rivets were used to hold the fibreglass matting firmly in place with the aid of metal stay backing plates (made of strips of scrap metal).
At least two layers of fibreglass matting were fixed to all inner walls of the oven. Loose edges of the matting in the corners of the filing cabinet, etc, were also fastened down securely using strategically placed and riveted metal stays.
A second continuous layer of aluminium foil was then applied over top of the fibreglass matting on all sides and doors and again sealed with aluminium tape. Rolls of fibreglass matting covered with aluminium tape were used to form effective door seals.
The aluminium foil and fibreglass matting sheet insulation arrangement proved to be extremely effective.
All further potential heat leaks around the doors, edges of elements, enclosures, inspection hatch, etc, were inspected and sealed with insulation and heat safe aluminium tape to ensure thermal efficiency.
A hole for an inspection hatch was cut into the top of the upper door. Two lengths of aluminium railing was used as the upper and lower slide guides of the hatch and a piece of rectangular scrap sheet metal with a bolt punched through it was used for the inspection hatch door itself.
An old metal induction motor was modified to act as a slow turning heat circulation fan. This was attached to the top of the oven and covered with the enclosure from an old burnt out PC power supply.
Holes were drilled into the skin of the oven to allow for insertion of thermometer probes. A sturdy hanging rack was also attached to the inner ceiling for hanging metal parts or project materials for heating.
There you have it! A hacked box of leftover as well as collected junk, stuck together with a handful of rivets …. The random combination just happens to function fantastically as a DIY oven!
Operation and Capability of DIY Oven
The filing cabinet oven is capable of reaching and maintaining a working temperature of 500°
Various temperatures and rates of heating can be selected by energizing various combinations of the five bar heat elements within the filing cabinet oven. Full power is rated at 2000W, but standard operation usually runs around 1200-1600W (ie: one or two of the element bars can usually be turned off after pre-heat).
We routinely operate the oven at 400-450°F (~200-230°C) for baking and curing electrostatic powder coatings on CNC machined aluminium and steel parts. At this temperature over a 20-25 minute cycle, the metal of the outer surface of the oven barely even gets warm. Even after one hour of operation, the sheet metal skin of the cabinet only gets warm to touch, but never uncomfortably hot. The thermal efficiency of the internal insulation is surprisingly high.
While making the oven, our concerns were for overly high temperature on the outer skin and the risk of fire in our workshop. For this reason, we also fitted the insulated false floor. But despite the oven being so hot on the inside, we have become quite less concerned about any risk of fire after witnessing how low the outer skin temps remain.
Pre-heating is extremely fast. Our standard operating temperature of 400°F (~200°C) can be achieved within less than 5 minutes at full power (ie: using all 5 heating elements). Following pre-heat, a steady operating temperature can usually be maintained even after switching off one or two heating elements (depending on season).
The oven does not draw air from the outside at all. The heated air is contained within the oven and evenly recirculated using a slow speed metal fan protruding into the oven from the top surface.
And damn … did we mention this oven was made from an old rusty filing cabinet for under 50 bucks!?! And that an industrial oven of the same size which would only achieve the same thing, would set us back well over $5,000-8,000!?
Anyway, you get the idea. The outlay for this DIY project was limited and the end results were phenomenal!
WARNING: This DIY project is potentially (extremely) unsafe! It involves equipment requiring wiring with mains power to allow the oven to operate at high temperatures. A recipe for disaster and a serious risk of electrocution, serious burns and fire during fabrication and/or operation. This article and the photos contained in it are for interest purposes only. We are not responsible for loss or liability as a result of peoples using the information presented. Copying this project may not be safe and may lead to serious damage, injury and/or death!