How to Make an Outdoor Griddle

Home griddles are becoming more and more popular. They are an awesome way to make food when entertaining a group of people. They basically are a big piece of steel with burners that heat the steel. The big piece of steel is what makes them able to cook lots of food at once and sear foods with ease.

A grill is great for when you want to cook foods directly over coals or flame but a griddle can cook all those same foods plus more. Such as searing steaks, kabobs, fajitas filling and even stir-frys. Another benefit is it keep all the cooking smells and fumes outside.

In this Instructables I'm going to build an outdoor griddle from scratch including the burners. The whole thing will be made from stainless steel except for the griddle cook plate itself, which will be made from mild steel. The reason for this is stainless steel is a poor conductor of heat and doesn't season well (i.e non-stick).

This build requires a welder but it is possible to make it with out welding and just bolt all the parts together or using a propane torch to braze certain parts together.

These are the tools and materials I used but this is just a list, certainly there is more than one way to build this:

Materials

• 1" x 1/8" angle stainless steel
• 4" wide 18 gauge stainless sheet steel
• 1" x 1/8" flat stainless steel stock
• 4 casters (2 with locks)
• 1/4" steel plate with mill scale removed
• 2" x 1/8" flat mild steel stock
• 1" x 1/8" angle steel
• 3/8" round stainless steel rod
• 1/4" round stainless steel rod
• Electronic BBQ ignition system
• Stainless steel bolts and hardware

Note that all the stainless steel used was 304.

Tools

• MIG Welder with stainless steel wire and mild steel wire
• Angle grinder with cutting disc and flap discs
• Metal Bandsaw
• tap and die set
• Drill and drill bits
• Center punch

Check out an in depth build video of the griddle from start to finish, the written steps follow:

The first thing to build was the frame, I sized the griddle to be 22" x 18" so the frame would match those dimensions. The frame is made from 1" x 1/8" stainless steel angle and 1" x 1/8" stainless flat stock.

I wanted the griddle to be portable so it could be tore down for storage and transportation. The front and back were made first, it was important to make sure to check for squareness as you are building and correct as needed. These pieces were all welded together. Then the front and back were bolted together, I did this by cutting to length some of the stainless flat stock and clamp them in place to check for squareness and adjusted as needed. Measuring across the diagonal is the best way to check for squareness. If the two measurements are the same length then it means it's square.

Holes were drilled on the flat stock that makes up the sides of the frame. Then the holes had threads cut with a 8-32 tap. This allows the front and back to be bolted together making a frame. If you don't want to tap holes a bolts and nuts works just fine too.

It should be noted that stainless steel is really hard to work with, anneal the metal with a blow torch really helps when drilling it.

After the main part of the frame was built, some short pieces of stainless angle were welded to the legs so the casters had a place to be attached. The casters I used have a threaded rod so it was as simple as drilling out the holes and then bolting in place.

For the top of the frame where the burners would be mounted some 4" 18 gauge stainless steel was cut and then welded on the two sides and back. The front was made to be removable by tapping some holes so bolts could be used to secure it.

Warning working with propane can be dangerous, DO NOT attempt this unless you have some idea of how propane burns. I take no responsibility if you hurt yourself, property or others while trying this. This information is provided as reference only. Buy some burners if you do not have the skill or knowledge to make them.

At a minimum safety glasses, non flammable clothing must be worn and this burner should only be operated outside.

To build the burners I posted a whole other Instructables on my other account (https://www.instructables.com/id/How-to-Make-a-BBQ...) with detailed instructions and video but here is the process as well:

This is what I used for materials to build one burner:

• 1" x 1/16" stainless steel tubing (could substitute this with regular steel but stainless will last longer)
• 3/4" to 1 1/2" black iron reducer fitting
• 1/8" brass NPT pipe nipple
• 1/8" brass NPT end cap
• 1/8" ball valve rated for gas
• 3/4" steel bar stock
• Low pressure BBQ regulator and hose (depending on how many burners you hook up you will need to increase the capacity of the regulator)
• Flare fitting to go from the propane hose to 1/8" NPT thread
• Propane Tank
• PTFE tape or pipe dope

Tools:

• Drill and Drill bits Small Drill bits (1mm or 1.2mm) - you can get set off amazon if you can't find them locally
• Tap and Die set (8-32 tap and 1/8" NPT tap)
• Welder with cast iron welding rods or MIG Welder with stainless steel wire (this makes things easier but it is possible to braze the parts together as well with a propane torch)
• Bandsaw or hacksaw
• Center punch
• Angle grinder with cutting disc

So lets talk about theory, at least in my layman's terms

This burner design works off the venturi effect, as gas is being forced out through a small orifice mounted at the end of the burner, it pulls air along and mixes inside the burner tube. The mixed propane and air then is forced out of the burner holes or slots and when ignited it burns.

Propane needs to mix with air to burn at a specific ratio, but with trial and error I was able to get the burner to burn with a nice blue flame. If you get a flame with yellow or orange, it means that there is un-burnt fuel and not enough air has mixed with the propane to get proper combustion. The size of the orifice hole is very critical to the size of the tube, if the tube is too small and the orifice hole too large you get incomplete mixing and incomplete combustion.

For this design I tested many different orfice holes, from:

• 1/32" - too small - very small blue flame
• 1/16" - too big - lots of yellow but a very powerful flame
• 0.8 mm - too small
• 1.0 mm - just right - no yellow flame
• 1.2 mm - just right with a bit of yellow but a very strong flame

I landed on either a 1.0 mm or 1.2 mm orifice hole.

Orifice Assembly

The orifice assembly is made from

• 1/8" brass NPT pipe nipple
  • 1/8" brass NPT end cap
  • 1/8" ball valve rated for gas
  • 3/4" steel stock

The center of the 1/8" brass NPT end cap was center punched and then drilled out using a 1mm or 1.2mm drill bit, cutting oil was used too. This hole is the orifice and propane will flow out from this hole at high velocity.

Also pro-tip, if the drill bits are too small for the chuck of your drill use some metal tape and wrap it around the drill bit so it will make the shaft large enough to be grabbed by the chuck.

Center punch the 3/4" steel stock and drill a hole that corresponds to the 1/8" NPT tap. Using lots of cutting oil cut threads into the hole. This hole will thread the 1/8" brass NPT pipe nipple. Once the pipe nipple has been threaded through the hole, cap off the opening of the tube with the cap that has the orifice hole drilled in from a previous step.

Thread the ball valve onto the other end of the nipple. Be sure to ensure a leak free seal between all the fittings by using PTFE tape or pipe dope to seal the threads.

Building the Burner Tube

The body of the burner is made from a piece of stainless steel tubing, stainless is really hard to work with as it work hardens. I first was going to drill burner holes in it but it would take far too long and far too much work so I decided I would cut small thin slots in the tube spaced 1cm apart for the burner "holes". I used my portable bandsaw and made short work of this but a hack saw could be used too.

The end of the stainless steel tube was heated and then bent closed in a vice. This allows the burner tube to be crimped and "capped" off, making a flat spot where a hole can be drilled and used for mounting the burner. The end of the tube was welded shut after crimping (this could be brazed as well).

Next the tube was welded on to the 3/4" to 1 1/2" black iron reducer fitting, the reducer fitting makes for a great burner intake for air and mount for the orifice. Two 3/4" steel tabs were welded on to the sides of the reducer that were tapped with a hole (3-32 bolts is what I used) to accept a bolt for mounting the orifice assembly. Again if you don't have access to a welder this could be brazed and the holes could be tapped directly into the end of the reducer fitting. I chose to weld on some tabs as it made it easier to work with.

A note about welding the black iron reducer fitting: these fittings are typically cast iron which do not weld very well or easy. Since I am just tack welding, it's not really an issue, also the cast iron should be preheated before welding. I am using a MIG welder with stainless steel wire, which I have heard that can be used to welding cast iron. So far I have had no issues with cracking.

Line up the orifice of the orifice assembly so it's in the middle of the 1 1/2" opening of the reducer fitting, you want the propane to shoot straight down the burner tube so it can mix with air, clamp in place and mark the holes with a marker. Holes were drilled into the orifice assembly that match the steel tabs with the tapped holes so the orifice assembly could be bolted to the reducer fitting.

Hooking Up the Burner and Testing

To hook up the burner to the propane I used a fitting that went from the flare fitting on the propane hose and regulator to 1/8" NPT threads, in my case the ball valve. This will depend on the fitting you used so just use what I have done as a guideline, check your local area for a propane supplier or fitting shop and they will be able to get the proper fittings for you.

The propane regulator I used was low pressure one for a BBQ, it needs to be large enough to handle the capacity of the number of burners, in this case I sized this regulator to 80,000 BTUs, more than enough. It's better to have excess capacity than not enough. Remember the flow rate of the regulator is different than the pressure it can provide. Low pressure propane regulators (less than 1 psi) are very common and are plain gray or silver in color, a high pressure regulator is red in color. An adjustable high pressure regulator could be used as well but it depends on how forceful you want the flame to be.

Clamp the burner securely into vise or table before testing.

Turn on the propane on the tank and open the ball valve 1/4 of a turn ,gas should start flowing, using a BBQ lighter the gas was ignited flowing from the slits cut in the burner tube. There should be a nice blue flame if everything is working properly. I tried adjusting the flow of gas to make sure the flame is burning correctly, it should be blue when turned up low or high. Changing the size of the orifice or the position of the orifice assembly was done to tweak the setup.

Burner Assembly

Now that the burners work, it's time to plumb and put the burner assembly together. All the fittings used were 1/8" NPT, look the pictures show how the whole system was plumbed. Basically each burner has it's own valve and then each burner was plumbed to a manifold. Since there are a lot of individual fittings to assembly I used pipe dope/thread sealant instead of PTFE tape.

Plumbing the Burners

Once the burner was working properly, three of them were plumbed together using 1/8" NPT fittings, see the pics on how this was done as it's fairly simple. Each burner had it's own ball valve and was plumbed into a manifold.

The ends of the burners that were clamped off had a piece of flat stainless steel welded in place and a hole drilled for mounting. A piece of 1" angle stainless steel was welded to the back of the frame with three holes drilled for mounting the ends of the burner tubes.

At the front of the frame two pieces of angle steel were welded in place with holes drilled and tapped to accept a bolt. A piece of 1" angle stainless steel would be bolted to these two pieces of steel with the tapped holes. A bolt with a nut could be used as well. This piece of steel is used to keep the front of the burner assembly mounted and supported. The bolt allows for adjusting the tightness and height of the burner.

The burner assembly was then placed onto the back mounting piece of stainless steel and bolted in place. The front of the burner assembly was then supported using the angle bracket and mounted with bolts. The bolts were tightened until the burner assembly was snug.

A universal BBQ igniter was installed so a push button start would light the griddle. This really give the griddle a professional feel. I won't go into detail on how to install it as the instructions that come with it are very straight forward, you can buy them at Walmart, Amazon, Home Depot etc..

The griddle is a big heavy piece of steel, don't drop it on your toes! 1/4" thick is what I went with so there would be lots of thermal mass and it will prevent hot spots by conducting the heat over a large area. It's important to use mild steel as it will season like a cast iron pan.

Steel comes from the manufacturer usually hot rolled, meaning it was heated and then worked into shape. This means the steel had a coating of mill scale left on it from the process. This mill scale is super tough and needs to be removed before the cook top can be used. The easiest way is to soak the steel in acid, in this case I used vinegar. It will take a day or two but it will come off. I built a box from some wood and lined it with garbage bag so I could soak the piece of steel in vinegar. Wash with lots of water and dry or else it will rust like crazy.

Some 2" x 1/8" mild steel sides were welded to the 1/4" plate on three sides. The front of the 1/4" plate had a piece of 1" x 1/8 angle steel welded in place that channels the oil and grease into a holding container.

Some 3/8" stainless steel rod was welded to the corners of the cook top so it can be mounted to the frame. The frame has matching holes drilled out where the cook top will sit.

The side tables are a nice option to the griddle station. They were made to be fold-able for storage. I could have used wood to make the side tables but I like the idea of having something that would stand the test of time and easy to wipe down so I made them from stainless steel as well.

They are very simple, just a piece of 20 gauge stainless steel sheet metal welded to a stainless steel angle frame.

To install all I did was weld some stainless steel hinges to the top part of the frame and then bolted the side table to the hinges. Two pieces of stainless steel were drilled and welded to the bottom of the frame so a stainless steel support rod could be used to support the side table. The rod just wedges into the bottom of the table and holds it up.

Some short pieces of 1/4" stainless rod was welded to the front for hanging cooking utensils on.

Some finishing touches needed to be completed, some grinding and smoothing of the welds and a polish of all the stainless was done with some metal polish.

The final step before the griddle can be put to use is seasoning the cook top. Since the cook top is a piece of 1/4" mild steel it will make a nice non stick cooking surface once it is seasoned. Seasoning the griddle is no different than seasoning a cast iron frying pan. The griddle was heated to a medium heat and some canola oil was rubbed on all the surfaces including the sides with paper towel or cloth. Then let the oil smoke and cook off, repeat the process a few times. What this does it creates a non-stick surface as the oil is polymerized to the hot steel, think of it as coating the steel with a hard plastic.

The griddle is ready to be used, the more the griddle is used the more non-stick it will become!

Also included are a few pictures of the griddle taken apart to show how portable it is.

Here are a few photos of the griddle in action. It works amazing, better than I hoped. Retains heat so well and makes the best smash burgers. The seasoning is very non-stick and I can fry an egg over easy with no issues.

I hope you enjoyed this build an check out my youtube channel for food related videos that I will be making using this griddle in the future.