Change out a rear Shock Absorber on a W123 and I sheared/broke one of the Bolt Heads off.
I decided to try to drill it out with the Trailing Arm still on the Car.

I center punched what was left of the Bolt OK but I have always had trouble drilling a staright hole even when what I am drilling is on a Bench and I continued My tradition and got the Hole off center and likely at some Angle.

I only had 2 choices of Easy Outs (see pic) that I already have and as the M10x1.5 Bolt is not much larger in diameter than an 3/8" Bolt the Easy Outs in that size are not very sturdy.

So I one of the Easy Outs and it did not work and I stopped before I broke it.
I drilled the hole out larger and tried the larger Easy Out and it jus sort of reamed out the metal.

I tried drilling a hole on the outside of the Threads to see if that would relieve it a bit and tried the larger Easy Out but no luck.

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84 300D, 82 Volvo 244Gl Diesel