63c is very safe.
You are good.
The temperature at which the processor will throttle to protect itself is around 100c.
The metric that you want to monitor is vcore. It will go up as the clock rate is upped.
As of 10/11/16 here are the odds of I7-6850K
overclocking at a reasonable vcore around 1.35v.
4.3 83%
4.4 53%
4.5 21%
4.6 3%