Spring Pin removal from speedo gear box

I'm trying to service the speedo gear box so I can replace a worn pinion gear. I have managed to source the pinion (number 16 in the attached) but am stumped as to how to remove the spring pin (number 14) from the blind hole. I have already broken a drill bit attempting to drill it out and have since been told that the spring pin is harder than the case and will be nearly impossible to drill out. It looks as though it has been designed not to be pulled apart despite what the parts book implies. One suggestion was to flatten the rounded area opposite the blind hole and drill through and then punch out the spring pin from that side (see second photo). That came from my local machinist, but he didn't want to attempt it. Has anyone ever done this? Does anyone have any alternate suggestions? I'm not that keen to buy a used speedo gear box as it could have the same worn pinion gear as my current one.  Thanks.  

Your machinist was correct. 

 

I have done it once on a z1 drive and I believe I did drill from the other side and tapped it out. I remember trying to drill out the pin also along with a few other bad ideas.

You don't drill them, you tap them, stud them and using a collar. Pull them out. It's a split pin with teeth.

Thanks for the advice chaps. I'll let you know what method I use and how successful it is.