How to fix a chair in 20 min using a Makerbot

I have this office chair that lost one of the bolts that holds the backing on the back support so that it keeps falling down. It's annoying so I can't lean back in my chair.

So I was thinking, "Hey (myself), I have a makerbot! I'll just design and print a new bolt to hold my chair backing together". I don't usually have conversations with myself but it was a lightbulb moment.

First, I took my calipers and started measuring the hole dimensions. Total bolt length would be 30mm (1.2"), about 5mm diameter (M5), and about a 15mm (.6") bolt head diameter. I simply drew circles in sketchup, extruded them to the right height and made my first part. Exported as STL (with plugin), skeinforged it in RepG, fired up the Makerbot and printed it.

First print worked well but I realized I entered in the dimensions as radius not diameter so it was twice as big as I needed. So design, forge, repeat and I had a correctly sized stud. As you probably know towering small diameter pieces doesn't work too good since the plastic is still molten and the extruder head is pulling the stacked plastic. It basically corrects the overall shape and is still within the right dimensions but it's very wobbly. It fit! Unfortunately, it would pop out of the chair because it wasn't secured well.

Third revision I designed a slot in the head to make it more like the other bolt, I increases the diameter .2mm and printed again. This time the bolt actually turned out pretty well, although still wobbly, but hard enough to considered a part. This time I used the newly designed bolt and it screwed right in, probably by gumming up the threads in the chair with ABS.

So there you have it. Designed, printed, revised, and fixed a chair without even leaving my desk!