Had a job this week to remove a broken bolt. 3/4-10 x 4.5" long bolt, about 2.25" of thread in a blind hole snapped off just below the surface. The bolt is one of four that hold a pillow block bearing for the disc on a track chipper.

No way to weld something on to the bolt unless we disassembled the chipper to remove the disc so I drilled. First a small pilot at 1/4". The problem was from the top of the pillow block to the mounting pad was 2 5/16" but I was just able to grip the end of the bit to get almost through it. Once I got to a 3/8" bit I was able to drill all the way through the bolt. Then to 1/2" bit, luckily I was able to drill through the bottom plate too so it was no longer a blind hole. I figured I would drill up from the bottom with a 9/16" bit & it would catch & spin out the top. No such luck. I tried heating what was left of the bolt but no luck either. Drilled it to 21/32" which is the tap drill size & re tapped it very slowly.

Very limited working area but finally got it. I did recommend at one point to just drill it clean through at 3/4" & put a bolt & nut as it would be cheaper but customer said to keep trying to remove it.

First pic is the work area. Second pic is the pillow block. Third pic is the hole. I know it looks off but just the angle of the pic. Fourth & fifth pic is where the hole came through. I crawled in to drill up from here.