I bought an office chair a while ago that recently had a couple of bolts break off on the bottom of the chair. I'm not sure what the name of the types of bolts are but I need to find replacements for the bolts because the back of the chair is very unstable without the missing bolts. These bolts came preinstalled with the chair IIRC. Below is an image of one of the bolts as well as an image of the part of the chair that the bolts broke off from:
What is the name of this kind of bolt and where might I be able to find it?
UPDATE: As requested, here is the picture of the remaining unbroken bolt:
Width: 5/16in, Length: ~2 and 2/16in
I ended up using a hammer drill (on the drill setting not the hammer setting) to drill the broken bolts through the other side of the holes. I did end up dulling a couple of drill bits in the process though. Using needle nose pliers didn't work. I bought replacement bolts at a big box store b/c the local hardware stores I went to only had the hex head screws that could only be turned with a wrench.