I had one of the springs snap off of my MRC brakes. I plan on using these on my RekTek build (see link below), so I had to fix them. I've been working like a dog lately and decided to take some time off or regular duties and hit the machine shop.
The original springs were made of 0.10" titanium rod. I couldn't find that diameter, but I found some slightly beefier 0.125" stock.
These are the pics of the repair.
I drilled the new holes with a #31 bit 0.1200" so that I could get a good press fit.
I then put the titanium rods in some liquid nitrogen to cool and shrink them, and I heated the aluminum block up with a heat gun. I then lined everything up and gave a few good hits with the ballpeen hammer.
I'm pretty ....chuffed (is that what you say in the UK?) with the results.
originally I was just going to drill out the remaining piece of the titanium that was stuck. You can see that I started to do that. Then I remembered that the replacement was slightly larger in diameter and might be too close to the outer edge. I decided to drill the other side and offset the hole slightly to accommodate the larger dia. rod.
here you see the old spring on the right. I was able to pull it out of by hand. I had one broken spring and one intact. I didn't think the brakes would feel correct if I had different springs on the left and right so I pulled the spring out.