3/28/2012 UPDATE: Wow, thanks for the feature! As an update, the chair is still going strong 4 years later. I haven't had to do a thing to it, but my needs have changed, and I'm considering converting it to a lounge chair for my man cave. Thank you all again for the kind words. It was one of my more fun projects. Keep creating!

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Build a unique piece of furniture and recycle in the process!

I got the idea for this project after watching old seasons of "Top Gear". In the studio, the show hosts sit on seats taken from an old car, and recycled into living room furniture.

For my project, I wanted a unique office chair built from a car seat that could recline and rolls around like this example HERE.
Since I was a poor college student, I couldn't afford a $680 office chair, and instead set a budget of $40.

Total Cost:

Chair - $25
Base - $10
Hardware - $3
Plywood - free! (I already had it)

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$38!
The rest of the pages describe the steps I took to find the parts and build the chair. Enjoy and good luck!

Step 1: Find a Seat.

Obviously, the most important ingredient here is the seat. Here are some things to consider when choosing a seat:

Although the seat might look great in the car, keep in mind that its new home will be completely out of its element, presumably in a house, so make sure that the chair wouldn't look hopelessly dated in your home. (For example: A '67 Mustang chair might be pretty sweet in a Mustang, it might not look so good with your wife's Ikea furniture.) It's just something to consider.
Make sure your seat has a mostly square bolt hole pattern, and that all the bolt holes face straight down. If your brackets are asymmetrical, or angled (or, God forbid, both) you'll just be adding that much more complexity to the project. I was lucky enough to find a seat with mostly symmetrical bolt holes, making my base pretty easy to cut.
Try to avoid electric seats. If you want to able to use the chair's built in adjustment controls, it's much easier to pick a chair with manual controls. You might be able to wire up a system to power an electric seat, but that's out of the scope of this instructable. Sorry.

Then again, if you don't care about the controls, go right ahead with an electric seat.

Now that you know what to look for, where do you actually get a seat? Here's some ideas:

Ebay or Craigslist - These probably won't have the cheapest seats, but they will have the best selection, and you're not going to have to pull it from the car yourself. Keep in mind, though, that some cleaning will probably be required, unless the seat is brand new.
Auto parts stores - This will be the most expensive option, but if you really want a SPARCO race seat, or don't want to bother with used seats, you'll mostly like find one here.
Dig one up yourself at an auto recycling lot (like U-Pull-It, or something similar) - This is going to be your cheapest bet, and the option I chose. Bring a tool kit with a decent socket set, pay a small entrance fee (usually about $2) and start looking! You will have to look hard. The lots are huge, but most vehicles have been sitting there a while, and the seats are likely to be moldy, torn, and/or pretty dirty. After 2 hours of searching, my brother and I found this leather seat from a newer Infiniti that hadn't been beat up, ripped, or otherwise defiled. The company charges for seats based on features, not condition. Since my seat only had manual controls, it was just $24.99! What a steal!

Step 2: Find a Base.

Now that you have a nifty car seat, find yourself a base. I got mine from a surplus store for $10. Here's some stuff to think about when you're looking:

Like the seat, a simple bolt pattern and a flat top will make your life much easier.
Check to make sure the controls still work, if you want to use them, and that none of the components are rusted out, as that's just not safe.
It's unlikely that you'll be able to get just a base like I did. (I got really lucky there.) So make sure you can easily remove the office chair from the base, and that the chair arms aren't directly attached to the base. Make sure you have a way to dispose of the old chair before you buy it!

Step 3: Build and Assemble the Base Plate.

Now that you have the key components, start making your base plate. I used 3/4" plywood for my base. This is the thinnest you should go!

Set your seat down on the plywood, and measure the smallest possible square for the chair to sit on. You'll want to leave a bit of room around the bolt holes of the chair, in order to maintain the plywood's strength.

Use a circular saw to cut out your plate, then center it on the base. Set the chair on the plate, and mock up your seat before you start drilling bolt holes. Make sure the plate places the seat on the base in a comfortable position, and that the chair is more or less level.

NOW you can drill. Mark the positions of the bolt holes for both the base and the seat and drill them out. (It might be easier to completely mount the plate to the base, then do the chair.)

Hardware: I used four 1/4" diameter bolts for the base, and four 5/8" bolts for the seat. All the bolts were 1.5" long. These are just for reference, as your chair and base will undoubtedly vary from mine.

Make sure to use washers between the bolts and the wood. The wood will experience quite a bit of force when you recline, so spread out the load wherever possible.

Step 4: Finish.

Although you're technically done now, here's some other steps to add:

Paint the base. (Black will probably be your best bet.)
Clean your seat, if dirty. I used leather conditioner and leather cleaner to wipe away the dirt smudges. A good vacuum job took care of all the crumbs tucked away in the cracks.
If you kept the seat belt, staple it underneath the base and buckle it in! Although you probably won't want to do this all the time, it's just one more conversation piece on an already unique chair.

Now get out there and have fun with it!