We are currently renovating our bonus room into a combination office/playroom (aka Ploffice...;). We needed more seating as well as additional beds for guests when they came over. What we landed on was a basic metal bed frame design that could function as both depending on the situation.
I recently picked up a MIG welder and wanted to give a steel frame a try. Overall I loved how quickly this thing went together, but I learned a few things not to repeat in the future. On to the build.

Supplies

Tools

Supplies

Step 1: Create the Design in Fusion 360

All of my larger/complex projects start with a design in Fusion 360. This one was no different. We went with a basic tube steel frame with plywood to fill in the back and sides.

To get the bed in the room it has to fit in a very narrow doorway. I knew that the design needed to be modular and I made the bottom frame completely removable.
Looking back at the design there are a few things I should have changed, as well as recommendations if you are going to do something similar. 1. The sides should have been lower. Since this is being used as a large couch in addition to a bed it's hard to see over the sides when you are sitting at it. This would have been pretty easy to fix from the start. 2. You will see it at the end but I didn't have nearly enough bottom supports. In addition to not having anything to support the mattress at the very top and bottom, they were also not spaced close enough together. I wound up placing a scrap piece of plywood on top of the supports to give the mattress a firm foundation. If you were using a box spring you might be ok, but make sure and think through how much support you will need in the base before you build it (I sure didn't....)

Step 2: Cut the Metal Stock

The frame was made from 1in 16 gauge square steel tubing I got from my local steelyard. The pieces initially came in 24 ft sections which they cut in half for me.

Back at the shop, I used a Dewalt Portaband to cut the pieces to their final sizes. The tricky part was to keep all of the cuts square. If you are using a stationary metal bandsaw or an abrasive saw then this will be pretty easy. Just make sure you are taking your time with any powered hand tools.

To prep the metal for welding hit all the edges and sides with an angle grinder. This gives a great clean surface for the welding.

Since I don't have a large metal table to weld too I went with the largest work surface in my shop...the floor. My floor is completely flat so had to be pretty careful to keep all pieces square.
These magnetic corner pieces were a huge help. But any type of square/clamp combo will work.

Step 3: Weld the Metal Frame Together

For welding, I used a brand new Lincoln Electric 140 Pro Mig. This was only my second time welding with the machine so it took a little bit to get my settings dialed in. I wound up at the lowest wattage and almost the slowest speed setting to get a good consistent arc/weld.

Make sure and test your settings out on a scrap piece of metal before starting to save grinding away lots of mistakes later.

I'm no expert by any means, but I did wind up getting some pretty good welds. I would take the frame into place first. And then after checking for square I went back and welded all the joints, making sure to alternate sides to (hopefully) account for the metal warping from the heat.

Step 4: Break It and RE-Make It

So even though this was one of my very first welding projects, the biggest mistake of this build wasn't from welding. It was measuring... or lack of it.

I wound up replacing 76 in with 67 in for the long supports. Which made them WAY too short.

The best workaround I came up with was cutting the frame in half and then welding the frame back together with a 9 in piece inserted between the sides.
I didn't do the best job keeping it exactly parallel to the other pieces, and there were probably some better ways I could have held everything in place. But once everything was ground down and painted you don't really notice it (unless you really looking for it).

Step 5: Create Metal Brackets

The entire bottom will be attached with corner brackets that will be welded at the bottom and then bolted into the frame.

To build the bracket I used some 1 in wide 1/8 in thick stock. Two pieces were cut out and welded together at a 90-degree angle to make a simple bracket that would attach the front of the frame to the two legs.

I drilled a 1/4 in hole with a drill press to use nuts and bolts to attach everything together.

Step 6: Weld the Bracket Into Place

With the brackets made and one side drilled out I welded them into place.

Step 7: Attach the Bottom Supports

I attached 4 supports to the bottom frame. Again this should have been way more with how the mattress would sit on top.

The supports were attached to the back frame with another bracket. This was probably pretty overkill but I still have left over stock and it was pretty easy to weld these into place.

Step 8: Cut the Plywood Inserts

The majority of the bed is taken up by simple rectangular inserts of 3/4 in plywood. These were ripped down to size with a circular saw with the Kreg Rip Cut. I used a hand saw to cut them to length since I couldn't fit the piece (safely) on my table saw.

Step 9: Cut Small Metal Supports

To attach the wooden inserts into the frame I used pieces of angle iron that were cut to about half an inch. I could then insert a screw through the metal support into the wood to keep everything in place.

Looking back again this was overkill. I could have just drilled directly through the frame into the side of the plywood and it would have held fine enough. I was worried that I would split the plywood and the screw connection wouldn't be strong enough for what I needed.

Step 10: Clean and Paint the Frame

To prep the frame for paint I first used Acetone to clean off any grease.

Then I used a self-etching primer over the entire frame before applying several coats of an enamel black spray paint.

Step 11: Attach Wooden Inserts

With the frame dry, I drilled holes into all the inserts and then screwed the panels into place.

Step 12: Fix the (Lack) of Supports

Even though the twin mattress has some support and spring built into it, you can see how it's easy to push it between the supports. I fixed this with a scrap piece of plywood that works kind of like a small box spring. Make sure to add more supports to your build!

Step 13: That's It

I learned a ton from this build. Working with metal was a blast, the pure speed of putting things like this together is crazy compared to woodworking with traditional joinery. I'm looking forward to building more furniture with metal frames in the very near future!

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