How to Make an Auto Seatby Russell Wood
Having a truly custom car means that everything is custom, including the interior. Building a custom seat may seem like a daunting task, but if you have basic welding skills, use the right tools and take your time, the job can be done.
Build a set of tabs for the floor mounts. Take the flat steel and cut it to length with the angle grinder. The mounts should have enough room for the bolt to go into the floor, as well as room for the round tubing, so depending on the size of your factory seat bolts, at least 2 1/2 inches. Then drill holes for the factory bolts and mount them to the factory seat mounts in the floor.
Bend the tubing so that it is level to the floor and connects two of the floor mounts. Do this to each floor mount so that you end up with two hoop shapes per seat. Tack-weld them into place. (A tack weld is a small weld that holds two pieces of steel together but is easy enough to break if you need to reposition something later.)
Connect the hoops you just made with round tubing. This will give you a square base to mount the seat body. Tack-weld the hoops into place as well.
Create a template out of cardboard for the base of your seat. Form it so that it contours to your body but also suits the vehicle. Continue this process for the back of the seat. Use one piece of sheet metal to make the back and base. If you want to add side bolsters, make them on the template and mark where your bends need to be.
Transfer your cardboard template to the sheet metal, including all bend marks. Cut it out using the tin snips or plasma cutter.
Using the marks you made in Step 6 as a guide, bend the sheet metal in the sheet-metal brake.
Tack-weld the seat base to the seat. Position it for use in the vehicle--remember, you will be sitting in it, so make it comfortable. Once you're secure with the positioning, finish-weld the entire seat. (A finish weld is your final weld for the material and should be a smooth, consistent weld that goes around the joint. A well-penetrating weld will have heat marks and should look like a stack of dimes.)
Spray the contact cement to both the seat and the 2-in. foam. Once the contact cement gets tacky, place the foam onto the seat.
Use an angle grinder, then the sandpaper on a sanding block, to grind the foam down to the desired shape. Take the seats to an upholstery shop to get the seats stitched and wrapped.