DIY Stainless Steel BBQ With Double Layer Bottom

DIY a Stainless Steel (AISI 304) Barbecue with double layer bottom.
The second level layer protects the barbecue's bottom from

overheating,
dilation,
deformation,
and reduce the losses of the heat.

Barbecue dimensions 500x340x110mm

Base dimensions 510x350x690mm

Total height Base+BBQ 740mm

What is Stainless Steel in short

Stainless steel is an alloyof iron which contains at least 10% chromium (Cr).

This addition of chromium defines the unique properties stainless, corrosion and heat resisting.

The chromium content of the steel allows the formation of an invisible,corrosion-resisting chromium oxide film on the steel surface.

If damaged mechanically or chemically, this film is self-healing, providing that oxygen, even in very small amounts, is present.

A common form of rusting stainless steel is after the stainless steel has been exposed to very high temperatures (400-850°C) or (750-1550°F).

If this happens, sensitization can occur which is where the carbon and the chromium bond together in the stainless steel and form carbides.

These carbides situate themselves at the stainless steel grain boundaries, and the grain boundaries become deficient of chromium.

With lower chromium concentrations at the grain boundaries, the chromium oxide protective film can become discontinuous and start rusting.

Chemical Composition

Stainless Type 430 (magnetic) also known as 18/c

Carbon 0.12% max.
Manganese 1% max.
Phosphorus 0.040% max.
Sulfur 0.030% max.
Silicon 0.75% max.
Chromium 16-18%
Nickel --

Stainless Type 304 (non-magnetic) also known as 18/8 for its composition of 18% chromium and 8% nickel

Carbon 0.08% max.
Manganese 2.00% max.
Phosphorus 0.045% max.
Sulfur 0.030% max.
Silicon 1.00% max.
Chromium 18.00-20.00%
Nickel 8.00-10.50%

Stainless Type 316 (non-magnetic) also known as 18/10 for its composition of 18% chromium and 10% nickel

Carbon 0.08% max.
Manganese 2.00% max.
Phosphorus 0.045% max.
Sulfur 0.030% max.
Silicon 1.00% max.
Chromium 16.00-18.00%
Nickel 10.00-14.00%
Molybdenum 2.00-3.00%

Step 1: Tools & Materials

Tools

For BBQ

Angle grinder 115 or 125mm -- (4 ½” or 5”)
Cutting disc ø115 x 1mm – (ø4 ½” x 0.04”) or ø125 x 1mm – (ø 5” x 0.04”)
Grinding Sanding Flap Disc
Snips (optional)
Sheet metal brake
Hand Drill
Drill Press (optional)
Drill bit ø4mm
Countersink or Drill bit ø8mm (to clean up the holes that will pass through the rivets)
Rivet tool
Tape measure
Vernier
Caliper
Square tool
Center punch
Pen Scriber
Mark pen
Clamp
Rope ø6mm about 4m

If you interested for a Sheet Metal Brake DIY

you can visit my Instructable pages

https://www.instructables.com/id/DIY-Sheet-Metal-B... simple version

https://www.instructables.com/id/DIY-Sheet-Metal-B... modified version with much more capabilities

For Base

Welding machine
Angle grinder
Grinding disk
Vise grips

Materials

For BBQ

Stainless Steel AISI 304 sheet metal

You can use any grade of Stainless Steel magnetic or non-magnetic AISI 430, 304, 308, 316

At any surface: shiny, glace, mat, satin.

Recommend: as cheaper choice, magnetic AISI 430

Recommend: for non-magnetic, AISI 304

AISI 308 (more expensive than 304) & AISI 316 (more expensive than 308) but I think, that it is an exaggeration.

1pcs 810X650mm thickness 0.7mm
4pcs 490x140mm thickness 0.6mm
20pcs Rivets ø4mm 5~10mm length

For Base

1. Angle iron 30x3mm about 6m

2pcs 508mm
2pcs 348mm
4pcs 600mm
4pcs 60mm
2pcs 448mm
2pcs 288mm

2.Flat bar 20x3mm about 0.5m

2pcs 250mm

3.Galvanized Steel Grid

1pcs about 500x400mm

4. Stick Electrodes 6013 2.5mm

Step 2: Plans

The red lines represent the bends

The green lines represent the cuts

Step 3: Plot the Sketch/plan, Onto Sheet Metal

Remember Safety First.

Welding Cutting and Grinding Tools are Dangerous!

Do it at your own Risk!

Use Always the Suitable Protective Equipment.

Before start the plotting process, be sure that the piece of sheet metal is orthogonal.

Plot the sketch/plan with cuts and bends onto sheet metal (AISI 304 810x650x0.70mm) using

square tool - caliper - rule - mark scriber - mark pen

At this point let's assume that all the cuts will be onto the bending lines.

Mark a line at 155mm distance from the edge of each side of sheet metal.

Do the same at 45mm distance and then at 25mm.

Mark the small cuts at the short sides at 175mm from the edge of the long sides.

Check the measurements and the squareness of the rectangular shapes.

A mistake at this step can cause an unexpected and irreversible failing at a later step.

Step 4: Preparation and Cutting

Lay out, and bore holes ø4mm at the 8 points that intersecting cuts and bends.

Use a piece of wood under sheet metal while drilling the holes to avoid damages at the bench.

The holes help to do clear cuts and stop's the tension of bending at the edges of each bend.

At the previous step we had had assumed that all the cuts will be onto the bending lines, but this isn't true.

The short sides need to be a little bit shorter, about 1mm from edges.

Having this tolerance we will be able to correcting small mistakes (if any), and assembly will done too easy.

In retrospect

At the long sides the cuts must done at the outer side of the lines and be adjacent to the line.
At the short sides the cuts must done at the inner side of the lines and be adjacent to the line.

The use of Inox cutting disc 1mm is required.

Secure the sheet metal so to can't move or vibrate.

The use of two pieces of wood and a clamp is good enough (see photos).

Start cutting slowly and stable, without any haste.

Yes I know what you can tell me:

So you did the cuts with a grinder, yes?

But how you made them perfectly straight?

You know it is very hard to make straight line with a grinder.

Yes I know that is a little difficult but ...this is only a thought on our mind.
Free up your mind from these thoughts and say yourself, yes I can do it.

Mark a straight line at a piece of sheet metal and secure it so as to can't move.

Start cutting over the line slowly and stable, without any haste.

Do the same again.

After some practice your cuts will be 99% straight.

This is a job that needs patience.

Use a Grinding Sanding Flap Disc and refine the cuts so to be smooth enough.

Step 5: Bending the Simple Bends

Using my sheet metal brake, did at first all of the simple bends, starting from long sides.

Adjust the clamping bar according to material thickness

Place the sheet metal over the break's bed - adjust and then tighten the brake.

Push the handle of bender till you have a 90° degree bending. (Need to push a little over the 90°)

I think that not need a more detailed description for this step.

You can follow the photos or view the video with the bending process here

Step 6: Bending the Box Bends

Now a change at the brake's setup is needed, so to be able to bend boxes

Replace the tightening bolts of clamping bar (brake) with stud bolts ø12x220mm.

Adjust the clamping bar according to material thickness and secure the stud bolts using lock nuts so can’t move.

Also needing:

flat bar 40x3x330mm,
flat bar 80~100x10x250~300mm,
a piece of stock steel,
some pieces of wood,
square tube or stock steel about 250~300mm

You can follow the photos or view the video with this bending process here

Place the sheet metal at the center of the brake's bed.

Place: flat bar - stock steel - wood pieces - flat bar

Adjust and then tighten the clamping bar.

Use a piece of wood between the long sides to increase the free space.

Bend the short side till the bender touch at long sides.

Place a piece of square tube e.g. 20x20mm or a piece of stock steel onto the bender and push to bend a little over the 90 degrees.

Do the same at the other short side.

At the last three photos you can see another similar way for this type bends,

using a piece of angle iron, some pieces of wood and two clamps.

Step 7: Corner Joints

For the making of the four corner joints we can use two pieces of the wastes that have left from cuts.

The dimensions of these pieces are a little less than the plan but isn't a big deal.

(80x100mm at plan, 77x100mm 2 pcs from one waste)

Do a mark line 100mm from the one edge.

Does a second cross mark line, at the middle of piece so to be divided in two equal segments.

Do the same at the second piece.

Do the cuts.

Now have four rectangle pieces almost equal.

Mark the points for the bevel cuts at 25 mm left/right from the corners at the short side.

Do the same at the rest three.

Use a Grinding Sanding Flap Disc refine the cuts and round off the corners so to be very smooth.

Lay out, and bore four holes ø4mm at each piece.

The centers of holes must be as follows:

20mm from left, 30mm from up, 20mm from right
20mm from left, 20mm from down, 20mm from right

Use a countersink to clean up the holes.

Using the sheet metal brake, bend the joints at 90°.

Step 8: Assembling

Use a rope and keep in place all pieces.
I start riveting, at first the four upper side corners and then the corners joints riveting one by one hole.

Drill/rivet one hole then other and so on.

I have used aluminum rivets ø4x10mm

Someone can be say:

why not, stainless steel rivets?

ok I agree, the stainless steel is always the best choice,

but if you have a rivet tool suitable for SS rivets.

I don’t want to buy one SS rivet tool, neither to kill my rivet tool using SS rivets.

Anyway, the aluminum melts at 660°C or 1220°F so the (Al) rivets isn't a so bad choice.

Step 9: Second Level Layer

For the second level layer needs four pieces Stainless Steel AISI304 490x140x0.60mm.

This layer is removable and after years and hundreds of grilling can be replaced easily and not need to make a new one barbecue.

Cut and bend the four pieces and arrange side by side at the barbecue's bottom.

Step 10: BBQ's Base

For the making of BBQ's base will need angle iron 30x30x3mm about 6m, flat bar 20x3mm about 0.5m and a piece of galvanized steel Grid about 500x400mm.

Angle iron

Cut to length 2pcs 508mm & 2pcs 348mm (the edges must be cut at 45°)

All the other cuts are straight except of the 4pcs 60mm that has a 45° bevel too at the top edge of the angle sides.(15mmm from top and 15mm from side)

4pcs 600mm

2pcs 448mm

2pcs 288mm

Assemble the upper frame where will sit the barbecue, using the 45°bevel cuts pieces

adjust and do tack welds

check the squareness - weld.

Mount /weld the feet, one by one at each corner of the frame, using vice grips and two pieces of angle iron.

Mount/weld the pieces for the down frame about 80mm from the feet edges (this frame can be used as shelf for the charcoals).

Flat bar 20x3mm

Cut two pieces 250mm length for the handles.

At distance 50mm from both edges, do a 90° bending.
Mount/weld the handles at the middle of the short sides of the upper frame.

Galvanized Steel Grid